Microsoft Word C001454e doc Reference number ISO 5344 2004(E) © ISO 2004 INTERNATIONAL STANDARD ISO 5344 Second edition 2004 07 01 Electrodynamic vibration generating systems — Performance characteris[.]
General
Clauses concerning the electrodynamic vibration generator, power amplifier, and overall system provide essential specifications that guide procurement These subclauses specify key requirements and parameters, enabling the specification writer to detail the necessary criteria for acquiring either a complete system or individual components Including comprehensive information ensures the system’s performance aligns with project objectives and facilitates a clear evaluation process.
When developing a specification, it’s important to understand that a single relevant standard may not encompass all subclauses needed for your application For instance, if you are only acquiring an amplifier, many system subclauses may be unnecessary, and only specific vibrator subclauses related to interface information might be required To ensure accuracy and completeness, it is recommended that the specifier thoroughly review the entire standard before selecting the relevant subclauses for their particular use case.
Subclause coding
A code appears after the title of each subclause as an aid to the reader and to the writer of relevant specifications This code has the form (X,y)
The entry at position X specifies the type of acquisition for which the subclause is applicable:
S only for system acquisitions, and
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C only if a component, vibrator or amplifier, is being acquired, but not if both are being acquired
The entry at position y specifies the type of use for which the subclause is applicable:
Symbol coding
Symbols used frequently in the text are coded as K g,h :
symbol K means F for force, t for time to temperature stabilization, I for current, V for voltage, Z for amplifier load, and d for distortion;
subscript g means s for system, v for vibration generator, and a for amplifier;
subscript h means s for sine, r for random, and i for impulse
General
Vibrators and amplifiers experience performance decline as operating temperature rises For continuous operation tests, equipment must undergo a conditioning heat run to stabilize its temperature before testing Exceptions to continuous operation should be explicitly noted, especially for air-cooled systems not suitable for high-altitude environments Additionally, certain vibrators risk overheating or failure when subjected to continuous sine operation at specific resonance points, such as pedestal-to-body or body-to-moving element suspensions.
System specifications (S,a)
An electrodynamic vibration generator system is primarily defined by its ability to generate force tailored to specific applications such as sine, random, or impulse vibrations When designing the system, it is essential to account for the mass of all necessary fixtures to accurately determine the required force output This ensures optimal performance and reliability in fulfilling the desired vibration testing purposes.
The system force generation capabilities shall be specified as follows:
for sine operation, the specified system force capability with test masses m 10 and m 40 is F s,s (see 5.3.2 and 5.4.2);
for random operation, the specified system force capability with test masses m 10 and m 40 and acceleration spectral density shape of 3.13 is F s,r (see 5.3.3 and 5.4.3);
for impulse operation, the specified system force capability with test masses m 10 and m 40 is F s,i
(see 5.3.4 and 5.4.4); the impulse acceleration time history to be produced (see 8.6) shall also be specified
If the power amplifier of the system is large, the system force capability and the vibrator force capability are the same
If the power amplifier is small, the system force capability is less than the force capability of the vibrator
System performance tests (see 5.3) are essential when acquiring and evaluating the entire setup, including both the power amplifier and the electrodynamic vibration generator These tests are typically conducted when both components are purchased together from the same supplier, ensuring optimal integration and reliable performance of the complete vibration system.
When a vibrator is likely to be used with other amplifiers, or an amplifier with different vibrators, it’s essential to specify the individual performance characteristics of both devices This ensures compatibility and optimal operation, particularly when used together now or in the future (see sections 6.2 and 7.3).
For general-purpose vibration generators used in wide bandwidth sine or random testing, no-load maximum acceleration current-to-acceleration distortion or fuzz should not exceed 1% to 3% However, for long-stroke vibration generators, especially those with rolling element guidance, a higher value of X may be acceptable to accommodate their specific performance requirements.
The system performance tests apply if the components are purchased from the same source
When the system is to be assembled from components, the components shall be individually specified and tested (see 6.1 to 6.3; 7.1 to 7.3)
When the test procedures are used, the acquisition of accurate interface data from the two sources and the calculation of the system forces shall also be specified.
System performance
force capability for continuous operation (see 8.2),
displacement capability, between mechanical stops,
The endurance tests (see 8.3) provide some assurance of reliable operation
The system performance test report shall give the information listed in 5.3.2 to 5.3.4
In the system sine conditioning run, as outlined in sections 8.2.1 and 8.2.2, the force Fₛ,ₛ and test mass m₁₀ are utilized to determine the time to temperature stabilization, denoted as tₛ,ₛ During this process, it is essential to monitor for any abnormalities or deviations from an uneventful run, ensuring accurate assessment of system performance and stability Proper analysis of these parameters helps optimize system functionality and identifies potential issues early.
During the sine endurance test (refer to section 8.3) at force F s,s, record the actual test duration, which should be at least 10 t s,s unless specified otherwise Throughout the test, measure and document temperatures of the vibrator body iron, moving elements, vibrator cooling mediums (air, water, oil), room ambient air, coolant-to-vibrator cooling system, and cooling systems for the amplifier Additionally, monitor and report the maximum and minimum main power voltage values Any abnormalities, deviations from normal operation, or issues identified during post-test inspection—such as damage or changes to the vibrator, cooling systems, or amplifier—must be described and documented to ensure proper assessment of the test's integrity and the equipment's condition.
Ensure that the system achieves the manufacturer's rated displacement and velocity
Measure the spill-over acceleration and ensure that the limit specified in 8.4 has not been exceeded
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The system's random conditioning run, conducted as described in sections 8.2.1 and 8.2.3, involves applying the force F_s,r to the test mass m_10 to assess temperature stabilization Key metrics include the time to achieve temperature stability (t_s,r) and identifying any abnormalities or deviations during the run Monitoring these parameters ensures optimal performance and highlights potential issues in the system’s thermal regulation process.
During the system random endurance test at force F_s,r, the actual test duration should be at least 10 times the specified endurance time, unless otherwise stated Throughout the test, record and report temperature readings of the vibrator body iron, moving element, cooling mediums (air, water, oil), room ambient air, coolant-to-vibrator cooling system, and the amplifier cooling system, along with the maximum and minimum power voltage values Document any abnormalities or deviations observed during the test and include the findings of post-test inspections to assess potential damage or changes to the vibrator, cooling systems, and amplifier components.
If the manufacturer's rated random displacement and/or velocity are greater than the sine performance rating, confirm that the rated random values have been achieved
Measure the spill-over acceleration and ensure that the limit specified in 8.3 has not been exceeded
The system impulse time history test requires generation of the specified acceleration time history by the procedure of 8.6
The system impulse endurance test (refer to 8.3.6) with a mass of 10 kg requires documenting the actual test duration, which should be at least 10×t seconds unless specified otherwise During the test, record the impulse acceleration time histories at both the start and end to monitor performance Additionally, note any abnormalities or deviations observed throughout the testing process After completion, conduct a thorough inspection of the vibrator and amplifier to identify any signs of damage or changes resulting from the test, ensuring the system’s integrity and reliability.
The system impulse endurance test was conducted with a mass of 40 kg, lasting a minimum of 10t seconds unless otherwise specified The impulse acceleration time histories were recorded at both the start and the end of the test to monitor performance consistency No abnormalities or deviations were observed during the testing process Post-test inspections revealed no damage or changes to the vibrator or amplifier, confirming the system’s durability under the specified testing conditions.
If the manufacturer's rated impulse displacement and/or velocity are greater than the sine performance rating, confirm that the rated impulse values have been achieved
Measure the spill-over acceleration and confirm that the limit specified in 8.4 has not been exceeded.
Calculated system performance
The calculated system performance requires the amplifier current and voltage capabilities as specified in 7.1 and confirmed by test in 7.3
Also required are the vibrator force capabilities as specified in 6.1 and confirmed by test in 6.2
Also required are the vibrator drive requirements as measured in 6.3
Referring to the amplifier capabilities and the vibrator requirements, two ratios are calculated: i,s a,s v,s
The available system force is F s,s =K F v,s , where K is the smaller of K i,s or K v,s , but is not greater than 1
Referring to the amplifier capabilities and the vibrator requirements, two ratios are calculated: i,r a,r v,r
The available system force is F s,r =K F v,r , where K is the smaller of K i,r or K v,r , but is not greater than 1
Referring to the amplifier capabilities and the vibrator requirements, two ratios are calculated: i,i a,i v,i
The available system force is F s,s =K F v,s , where K is the smaller of K i,i or K v,i , but is not greater than 1
Vibration generator specification (C,a)
An electrodynamic vibration generator's primary feature is its ability to produce the necessary force for specific applications, whether for sine, random, or impulse vibrations Accurate force calculation must also account for the mass of support fixtures to ensure optimal performance Considering these aspects is essential for designing effective vibration testing systems.
The vibration generator force generation capabilities shall be specified as follows:
for sine operation, the specified vibrator force capability with test masses m 10 and m 40 is F v,s
for random operation, the specified vibrator force capability with test masses m 10 and m 40 and with the acceleration density spectral shape of 3.13 is F v,r (see 6.2.3);
for impulse operation, the specified vibrator force capability with test masses m 10 and m 40 is F v,i
(see 6.2.4); the impulse acceleration time history to be produced (see 8.6) shall also be specified
For optimal maximum force capabilities, vibrators must be driven by an appropriately sized amplifier According to International Standards, this refers to a large amplifier designed to fully realize the vibrator's potential, distinguishing it from the smaller, system-specific amplifiers that may limit the vibrator's maximum force in practical applications.
Optionally, testing of the vibrator as a component may be specified, which is particularly important if the initial system includes an amplifier significantly smaller than the large amplifier, and if a future increase of amplifier size may occur
Optionally, the maximum value of the full current-to-acceleration distortion may be provided (see 6.3.2)
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Vibration generator performance
force capability for continuous operation (see 8.2),
displacement capability, between mechanical stops,
The endurance tests (see 8.3) provide some assurance of reliable operation
The performance of this clause is specified for a vibrator to be acquired as a component Optionally, it may be specified for a vibrator to be acquired in a system
This performance is demonstrated with a large amplifier The performance test report shall provides the information listed in 6.2.2 to 6.2.4
For the vibrator sine conditioning run (see 8.2.1 and 8.2.2) at the force F v,s and with the test mass m 10 , provide the time to temperature stabilization t v,s (see 8.2.2) and any abnormalities or deviations
Immediately after the sine conditioning run, take the data of 6.3.2 using the mass m 10
Change the test mass to m 40 , repeat the conditioning run until the same temperatures are achieved, and take the data of 6.3.2 using the mass m 40
During the vibrator sine endurance test at the specified force F v,s, record the actual duration of the test, ensuring it meets or exceeds at least 10 t v,s unless otherwise specified Throughout the test, measure and document temperatures of the vibrator body iron, moving components, cooling system (air, water, or oil), room ambient air, and coolant-to-vibrator cooling system Note any abnormalities or deviations observed during testing, and provide results from post-test inspections to identify potential damage or changes to the vibrator or its cooling system.
Confirm that the vibrator achieves the manufacturer's rated displacement and velocity
For the vibrator random conditioning run (see 8.2.1 and 8.2.3) at the force F v,r and with the test mass m 10 , provide the time to temperature stabilization t v,r (see 8.2.3) and report any abnormalities or deviations
Immediately after the random conditioning run, take the data of 6.3.4 using the mass m 10
Change the test mass to m 40 , repeat the conditioning run until the same temperatures are achieved, and take the data of 6.3.4 using the mass m 40
During the vibrator random endurance test at the specified force Fv,r, the test duration should be at least 10 times the standard period, unless otherwise noted Throughout the test, it is essential to measure and record the temperatures of the vibrator body, moving element, cooling medium (air, water, or oil), ambient room air, and the coolant-to-vibrator cooling system Any abnormalities or deviations observed during the test should be thoroughly documented Following the test, an inspection must be conducted to assess potential damage or changes to the vibrator and its cooling system, ensuring compliance with operational standards and identifying any signs of wear or malfunction.
If the manufacturer's rated random displacement and/or velocity are greater than the sine performance rating, confirm that the rated random values have been achieved
The vibrator impulse time history test requires the generation of the specified acceleration time history by the procedure of 8.6
Provide the m 10 vibrator impulse current and voltage time history waveforms for the specified acceleration time history with the test mass m 10
Provide the m 40 vibrator impulse current and voltage time history waveforms for the specified acceleration time history with the test mass m 40
The vibrator impulse endurance test with a mass of 10 kg was conducted for a minimum duration of 10 times the vibration period (at least 10 t_v seconds), unless specified otherwise During the test, impulse acceleration time histories were recorded at both the start and end to monitor performance Any abnormalities or deviations observed during the test were documented, and a post-test inspection was carried out to assess potential changes or damages to the vibrator The results confirmed whether the vibrator maintained its integrity or exhibited signs of wear or damage after the testing.
For the vibrator impulse endurance test with the mass m 40 , provide the actual time duration of the vibrator impulse endurance test (at least 10t v,s unless otherwise specified), the impulse acceleration time histories at both the start and the end of the test, any abnormalities or deviations from an uneventful test, and the results of an after-test inspection to determine if any changes or damage to the vibrator have occurred
If the manufacturer's rated impulse displacement and/or velocity are greater than the sine performance rating, confirm that the impulse values have been achieved.
Vibrator drive requirements
To ensure optimal performance, the vibrator powered by a large amplifier must meet the specified current and voltage drive requirements at the full designated forces This applies across various types of use, including sine, random, and impulse testing, guaranteeing accurate and reliable operation under all specified test conditions.
The vibrator drive requirements of this clause are specified for a vibrator to be acquired as a component Optionally, they may be specified for a vibrator to be acquired in a system
After completing the sine conditioning run (refer to Sections 6.2.2, 8.2.1, and 8.2.4) with test mass m10, perform a one-octave-per-minute sweep at the full specified displacement, velocity, and force within the designated frequency range Record the acceleration at the top center of the test load, along with the drive coil root-mean-square (RMS) current and voltage, which are essential for calculating the m10 curves described in Section 6.3.3.
To generate the M40 curves as outlined in section 6.3.3, change the test mass to M40 and repeat the conditioning run until consistent temperature levels are achieved Conduct an octave-per-minute sweep at the full specified displacement, velocity, and F_v,s force within the agreed frequency range Measure the acceleration at the top center of the test load, as well as the root-mean-square current and voltage of the drive coil, to accurately calculate the M40 response curves.
The maximum current needed for either sweep corresponds to the vibrator sine current requirement (I v,s) necessary to generate the force (F v,s) Similarly, the maximum voltage required for either sweep is defined by the vibrator sine voltage requirement (V v,s) required to produce the same force.
To ensure accurate testing, remove the test load and repeat the conditioning run until consistent temperatures are achieved Subsequently, conduct an additional one-octave-per-minute sweep at the full specified displacement, velocity, and force (F v,s) within the agreed frequency range During this process, document the moving element acceleration, drive coil root-mean-square (RMS) current, and drive coil RMS voltage for the m0 curves outlined in section 6.3.3.
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Perform a signal purity test, also known as a fuzz test, during a no-load run by carefully listening to the vibrator's acoustic output and observing its motion on an oscilloscope Look for any noise, distortion, or high-frequency fuzz on the acceleration wave, and report if fuzz exceeds 2% of the acceleration fundamental Common causes of no-load fuzz include poor or loose connections on the moving element or its suspension, which should be inspected and corrected to ensure optimal vibrator performance.
Provide the current-to-acceleration H f i ( ) and voltage-to-acceleration H v ( )f transfer function curves for the vibrator with masses m 0 , m 10 and m 40 , similar to those illustrated in Figure 1, from the data of 6.3.2
These temperature-stabilized vibrator curves are essential for sine and random testing, providing accurate performance data under controlled conditions For impulse testing, similar curves can be specified for cold vibrators, which serve as an effective starting point Generally, cold condition curves can be approximated from hot curves, aiding in test setup and ensuring reliable results across different operating environments.
H f , multiply the entire curve by 1,05 For H v ( )f , multiply the midband values by 1,25, tapering to 1,0 at f s and f t
At the end of the random conditioning run (see 6.2.3, 8.2.1 and 8.2.3) at the vibrator specified random force
F v,r with the test mass m 10 and the acceleration spectral density shape of 3.13, provide the driver coil root-mean-square random current and root-mean-square random voltage
Replace the test mass with m 40 and repeat the random conditioning run at the specified random force Fv,r on the vibrator Continue this process until consistent temperatures are achieved, ensuring the acceleration spectral density shape remains as defined in 3.13 Record the driver coil's root-mean-square (RMS) random current and RMS random voltage for comprehensive results.
The maximum current required for either conditioning run is the vibrator random current requirement I v,r for the force F v,r The maximum voltage required for either conditioning run is the vibrator random voltage requirement V v,r for the force F v,r
The vibrator impulse current requirement I v,i for the impulse force F v,i is the m 40 vibrator impulse current time history of 6.2.4, unless m 10 is specified (see 8.6)
The vibrator impulse voltage requirement V v,i for the impulse force F v,i is the m 40 vibrator impulse voltage time history of 6.2.4, unless m 10 is specified (see 8.6)
1 mechanical resonance of moving element suspension
2 mechanical resonance of moving elements a) Acceleration per unit current in the drive coil
Y transfer function, m/(s 2 ◊V) b) Acceleration per unit voltage across the drive coil
Figure 1 — Typical electrodynamic vibration generator transfer functions
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Vibrator maintenance (A,a)
Vibrator maintenance is required if the vibrator is to continue to provide the specified performance
Regular maintenance for optimal equipment performance includes inspecting and replacing air, water, and oil filters, water electrodes, distilled water, and water/glycol in the water tower Additionally, it’s essential to check and service flexible cables and hoses connected to the vibrator, field coils, and moving components Removing dust and dirt buildup, especially from the cooling air path, helps prevent overheating and prolongs the lifespan of the machinery.
Recommended periodic care also includes inspection and/or repair of the body-to-moving element suspension/guidance, and load-to-moving element mounting point inserts
Regular vibrator maintenance is essential, especially when the acceleration waveform significantly differs from the current waveform Such discrepancies often indicate cavitations in the liquid coolant or loose components within the moving parts Addressing these issues promptly can prevent equipment failure and ensure optimal performance.
Regular maintenance of vibrators is essential to prevent performance degradation; it is recommended to schedule monthly no-load, maximum acceleration, and slow sine sweep tests, with results properly recorded, as outlined in section 6.3.2 A properly maintained vibrator should produce clean acceleration waveforms without distortion or fuzz, while an increase in no-load fuzz over time indicates the need for preventive maintenance Monitoring these parameters helps ensure optimal performance and longevity of the equipment.
Vibrator maintenance should be provided by qualified personnel
Amplifier specification (C,a)
The amplifier current and voltage capabilities shall be specified as follows:
for sine operation, the specified amplifier current is I a,s and voltage is V a,s (see 7.2.2);
for random operation, the specified amplifier current is I a,r and voltage is V a,r (see 7.2.3);
for impulse operation, the specified amplifier current is I a,i and voltage is V a,i
Unless otherwise specified, the specified impulse current time history I a,i is the specified vibrator drive coil current time history when the vibrator is producing the desired acceleration time history with the mass m 40
If a system is being acquired for a specific type of use (sine, random and/or impulse) and if only the minimum size amplifier for that type of use is required, the size of the amplifier need not be specified It is understood that the specified amplifier current and voltage are the maximum required current and voltage for the specified vibrator at the specified force for the specified type of use
The system tests confirm that the amplifier performance is adequate Optionally, testing of the amplifier as a component may be specified
An oversize amplifier can optionally be specified to ensure optimal performance For each application, it is essential to specify the amplifier's current and voltage ratings, making sure they meet or exceed the maximum required vibrator current and voltage for the designated force This guarantees reliable operation and prevents overload conditions in the system.
If an oversize amplifier is being acquired in a system, the system testing confirms only the minimum amplifier size The amplifier shall also be tested as a component
Amplifier size is often expressed in terms of power, apparent power, or kVA, which represent the product of output current and voltage; however, these metrics are not effective indicators for selecting amplifiers in electrodynamic vibrator systems Instead, it is more useful to focus on four critical parameters: the available sinusoidal current (Ia,s), sinusoidal voltage (Va,s), random current (Ia,r), and random voltage (Va,r), all under a load with inductive properties of 7.2.
Not all vibrators operate at the same impedance level Some require high currents and low voltages and others require low currents and high voltages The use of impedance-matching transformers should be explored before writing a specification for an amplifier to be switched from one vibrator to another.
Amplifier test loads
Amplifier test loads are used to test the amplifier as a component They are expensive to construct, so they are usually used only when an appropriate vibrator is not available
Resistive test loads are unsuitable for evaluating amplifier performance when driving vibrators, as they do not accurately replicate the internal dissipation experienced during normal operation Both linear and switching amplifiers behave differently under real-world conditions, and resistive loads fail to mimic these dynamics Additionally, some switching amplifiers require an inductive load to function correctly, emphasizing the importance of using the appropriate load type for accurate testing and reliable operation.
Unless otherwise specified, the values of the resistive and inductive components of the amplifier test loads are selected such that the current lags the voltage by 60° ± 3 %
Ensure that amplifier sine and random test loads are equipped with adequate cooling to keep both resistive and inductive impedance components within 3% of the specified values throughout all testing For larger load sizes, circulating water cooling is typically employed to meet these requirements The cooling specifications are primarily determined by the demands of the conditioning and endurance tests, as outlined in sections 8.2.1 and 8.3.1.
In the middle of an amplifier's frequency range, its operation remains unaffected by frequency variations, making it possible to use a single inductor for both sine and random test loads By simply adjusting the test frequency, engineers can reliably evaluate amplifier performance across different conditions without changing the inductor This characteristic enhances testing efficiency and ensures consistent results during amplifier assessments.
The amplifier impulse test load has specific requirements that differ from those of the amplifier sine and random test loads (refer to sections 7.2.4 and 8.6) While cooling issues are less significant during impulse testing, it is essential that the amplifier impulse test load impedance properly matches the inductance and resistance of the vibrator to ensure accurate testing and reliable results.
To ensure the amplifier delivers sufficient voltage and current outputs under the most adverse loading conditions, the sine test load impedance must be specified accurately Proper impedance settings are crucial for verifying the amplifier’s performance and reliability during testing This guarantees that the amplifier can operate effectively, maintaining both voltage and current output standards even under challenging load scenarios.
= I when driven with a sinusoidal current at a frequency between 200 Hz and 1 000 Hz
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To make sure that the amplifier can provide, at the same time, under the most adverse loading, both an adequate voltage output and an adequate current output, the amplifier random test load shall have an impedance a,r a,r a,r
= I when driven with a narrow-band random current at a centre frequency between 200 Hz and 1 000 Hz
The filter used to generate a narrow-band random signal should have a bandwidth (b) between 3% and 5% of the center frequency to ensure precise signal filtering It must have steep filter skirts so that signals at frequency multiples are at least 50 dB below the center frequency signal, minimizing interference Additionally, the demodulation filter should have a time constant greater than 300 divided by the bandwidth (b) to achieve optimal signal processing.
The narrow-band random current (Ia,r) and narrow-band random voltage (Va,r), when used with the amplifier's random test load (Za,r), must have the same magnitudes as the wide-band random current and voltage that drive the vibrator This ensures accurate simulation of the acceleration spectral density shape of 3.13, crucial for reliable vibration testing Maintaining these equivalent magnitudes allows for precise replication of the spectral density profile essential for consistent test results and compliance with testing standards.
The design and fabrication of the amplifier impulse test load rely on first generating the desired impulse acceleration time history using the procedure outlined in 8.6 Additionally, it is essential to measure and record the vibrator's current and voltage time histories to ensure accurate test results.
Before conducting the actual impulse test load, it is essential to measure and optimize the response of a simulated impulse load Apply a scaled-down version of the required vibrator voltage to an amplifier connected to a simulated load with adjustable resistance and inductance Measure the load voltage and current waveforms, then fine-tune the simulated resistance and inductance values until their peak voltages and currents, as well as low-frequency wave shapes, closely match those of the original vibrator signals Achieving an exact match across the entire voltage time history may not be feasible due to frequency-dependent variations in vibrator inductance and resistance.
From the optimized simulated load, an actual impulse test load is calculated and fabricated It has the value
Accurate reproduction of current time history is essential since force is proportional to current Additionally, capturing the peak voltage is crucial, as avoiding voltage clipping ensures the primary amplifier requirement for impulse production is met.
The I a,i value used with Z a,i corresponds to the specified I a,i outlined in section 7.1.1, which replicates the same current time history as measured and recorded using the vibrator to produce the desired impulse acceleration profile Similarly, the V a,i value matches the specified V a,i from section 7.1.1, maintaining the same voltage peak and low-frequency waveform shape as the recorded vibrator voltage time history, though the overall wave shape may differ throughout the entire duration.
Amplifier performance
current and voltage capability for continuous operation (see 8.2),
satisfactory distortion and spill-over (see 8.4 and 8.5), and
The endurance tests of 8.3 provide some assurance of reliable operation
This performance is demonstrated for the specific amplifier being acquired The performance test report includes the following
During the amplifier sine conditioning run, use the specified test load Z a,s and apply the designated root-mean-square sine current I a,s and voltage V a,s Record the time to achieve temperature stabilization, t a,s, and monitor for any abnormalities or deviations from normal conditioning procedures.
When performing the amplifier sine distortion test (refer to section 8.5), measure the total amplifier sine distortion (dₐ,s) at the specified RMS current and voltage using the test load Zₐ,s Additionally, identify the magnitude of each harmonic component exceeding 1.0% Any distortion surpassing the spill-over limits outlined in section 8.4 should be documented accordingly.
The amplifier sine endurance test (see 8.3) involves operating the amplifier with test load Z a,s at specified RMS current and voltage, with a minimum duration of at least 10 times the test period (t a,s) During the test, record the minimum and maximum temperatures of the cooling air or water, as well as the cooling system, and note any abnormalities or deviations in the mains power voltage After completing the test, conduct an inspection to identify any changes or damage to the amplifier or its cooling system and document the test results accordingly.
For the amplifier random conditioning run, ensure the use of the test load Z a,r and the specified RMS narrow-band random current I a,r and voltage V a,r Record the time to achieve temperature stabilization t a,r and monitor for any abnormalities or deviations from normal, uneventful conditioning, as outlined in sections 8.2 and 8.2.3.
The amplifier random distortion test (refer to 8.5) evaluates the amplifier's performance using the test load Zₐ,r at specified root-mean-square narrow-band random current and voltage levels Key results include the total amplifier random distortion (dₐ,r, see 8.5.5) and the magnitude of each harmonic component exceeding 1.0% Any distortion surpassing the spill-over limits must be reported to ensure compliance with standards.
The amplifier random endurance test should be conducted using the specified test load Z a,r at the designated root-mean-square narrow-band random current and voltage levels The test duration must be at least ten times the specified time t a,r unless otherwise specified During the test, record the minimum and maximum temperatures of the cooling air or water flowing to the amplifier and its cooling system Monitor and document the minimum and maximum mains power voltage during testing Any abnormalities or deviations from normal operation should be noted, along with the overall success of the test Following the endurance test, perform a thorough inspection to identify any changes or damages to the amplifier or its cooling system.
The amplifier impulse time history test involves generating the desired impulse acceleration time history using procedure 8.6, measuring the vibrator driver coil current and voltage time histories, and preparing the amplifier impulse test load Z a,i according to procedure 7.2.4.
In the amplifier impulse time history test, the specified impulse current waveform, Iₐ,i, is applied to the impulse test load, Zₐ,i The test results include detailed impulse current and voltage time history waveforms, which are documented in the performance report to ensure compliance and accuracy.
The amplifier impulse endurance test involves applying a repetitive sequence of specified impulse time histories to the test load, with a minimum duration of at least three times the standard impulse duration unless otherwise specified During the test, the actual time duration, impulse current and voltage waveforms at both the start and end, any abnormalities or deviations observed, and the results of post-test inspections are documented to assess potential changes or damages to the amplifier.
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For the amplifier impulse distortion test (see 8.5) for the amplifier with the test load Z a,i with the gated sinusoidal wave train of 8.5.8, provide the total amplifier impulse distortion d a,i (see 8.5.9) and the magnitude of each harmonic component in excess of 1,0 % Distortion in excess of the spill-over limits of 8.4 shall be reported.
Amplifier maintenance (A,a)
Regular amplifier maintenance is essential to ensure optimal performance and longevity Key tasks include replacing air and water filters, water electrodes, and distilled water, as well as inspecting and replacing filter capacitors and hoses Additionally, it is important to replace water tower water or glycol and remove dust and dirt buildup, especially around high-voltage components and in cooling air passages, to prevent overheating and equipment failure Following these recommended periodic care measures will keep your amplifier operating efficiently and reliably.
For optimal amplifier performance, it is recommended to record maximum output voltage distortion measurements monthly Monitoring month-to-month performance degradation helps identify the need for preventive maintenance Always ensure maintenance is carried out by qualified personnel to maintain reliability and efficiency.
General
Tests to be specified and performed on systems, vibrators and amplifiers are described in Clauses 5, 6 and 7 This clause describes other considerations relating to these tests
Before drafting the purchase specifications, the equipment purchaser and the manufacturer must agree on the required tests and acceptable test reports for the specific equipment For instance, the purchaser may approve manufacturer’s endurance test reports on similar equipment as an alternative to conducting the specified endurance tests outlined in Clauses 5, 6, or 7.
Conditioning before data runs
When performance is specified for continuous operation, as is typical, the performance data shall be taken immediately after a conditioning heat run to stabilize the temperature of the equipment
Since the durations of impulse tests are short, impulse performance tests shall be taken on cold equipment (within 10 °C of room temperature) to maximize the available force
Perform conditioning heat runs with the equipment operating at maximum dissipation to ensure optimal performance For vibrator or system heat runs, operate at the specified force, starting with m 10 and then increasing to m 40, to thoroughly evaluate thermal stability For amplifier heat runs, run the system at the designated current and voltage into Z a,s or Z a,r as applicable to verify consistent operation under maximum load conditions.
Unless otherwise specified, cooling for the vibrator and amplifier shall be adjusted for typical warm weather conditions: low altitude air warmer than 35 °C and/or heat exchanger water warmer than 15 °C
For accurate temperature monitoring, install adhered thermocouples at two key points on the vibrator—one on the body iron near the load attachment end and another on the moving element close to the driver coil diameter Additionally, measure the temperature of the power transformer iron and the heat exchanger of the output power transistors on the amplifier These temperature readings are essential for ensuring optimal performance and preventing overheating of critical components.
To achieve temperature stabilization, it is essential to record temperature changes over time and calculate the temperature rise rates (ΔT/Δt) The temperature rise rates initially increase to a maximum point before gradually decreasing The time to reach temperature stabilization is defined as the moment when all temperature variations have halted, indicating a stable thermal state Monitoring these parameters ensures accurate assessment of thermal equilibrium in your process.
The temperature rise rates have decreased to 5% of their maximum values, indicating improved thermal stability The time taken to reach temperature stabilization is documented and used as the time base for endurance testing, as specified in section 8.3 For systems or vibrators, an accurate approximation is that the temperature stabilization time for mass m=40 is equivalent to that measured for mass m=10.
8.2.2 System or vibrator sine conditioning
Carry out conditioning at the sinusoidal specified force at the frequency of maximum dissipation, typically between 200 Hz and 300 Hz The time to temperature stabilization is t s,s or t v,s
8.2.3 System or vibrator random conditioning
Carry out conditioning at specified random force, with the standard random spectral shape of 3.13 The time to temperature stabilization is t s,r or t v,r
Carry out conditioning with the specified sine current and sine voltage with the amplifier loaded with Z a,s The time to temperature stabilization is t a,s
Carry out conditioning with the specified narrow band random current and voltage with the amplifier loaded with Z a,r The time to temperature stabilization is t a,r
Endurance tests
Endurance tests offer some evidence of equipment reliability; however, they do not guarantee conclusive results Equipment that successfully passes these minimum endurance tests is unlikely to harbor significant design or manufacturing flaws, indicating a higher level of dependability.
The sine and random endurance tests should be conducted for a duration equal to ten times the time required for adequate temperature stabilization, as specified in section 8.2.1 The vibrator or system endurance testing is performed sequentially, first using a test mass of 10 kg, followed by testing with a larger test mass of 40 kg to ensure comprehensive assessment of system durability under varying load conditions.
When temperature stabilization times (t g,h) are long, endurance test durations are typically limited to either ten times t g,h or 25 hours after stabilization, whichever is shorter It is common for specifications to require the test source to submit comprehensive reports detailing all endurance test procedures, results, current and voltage waveforms at both the start and end of testing, and noting any abnormalities or deviations observed during the tests.
As in 8.2.1, unless otherwise specified, the environment is adjusted for typical warm weather, low altitude conditions
8.3.2 System or vibrator sine endurance test
This endurance test consists of repeated cycles, each including a 30-minute run at full specified force with maximum dissipation, as outlined in section 8.2.1 Following this, there is a one octave per minute sweep at the specified displacement, velocity, and force, ranging from minimum to maximum force The cycles are repeated continuously to ensure the test duration meets the required length for accurate results.
10t s,s or 10t v,s (see 8.2.2) for the test mass m 10 and again for the test mass m 40
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8.3.3 System or vibrator random endurance test
Perform the endurance test at the specified random force with a standard spectral shape of 3.13, ensuring a duration of at least 10t_s or 10t_v (refer to 8.2.3) This test should be conducted for test mass m10 and repeated for test mass m40 to verify durability under specified conditions.
Carry out this test with the specified sine current and voltage (see 7.1.1) with the amplifier loaded with Z a,s for an amplifier endurance test duration not less than 10t a,s (see 8.2.4)
Carry out this test with the specified narrow-band random current and voltage (see 7.1.1) with the amplifier loaded with Z a,r for an amplifier random endurance test duration not less than 10t a,r (see 8.2.5)
8.3.6 System or vibrator impulse endurance test
The test is a repetitive sequence of cycles At the start of each cycle, switch on the field supply and allow it to stabilize for about 1 min, then generate a single full-force impulse time history Switch off the field supply off, and allow the vibrator allowed for 10 min to end the cycle Repeat the sequence of cycles for a time duration of not less than 10t s,s or 10t v,s (see 8.22) Carry out the test first with the vibrator loaded with the test mass m 10, and again with the test mass m 40 (see 8.6)
The test is a repetitive sequence of cycles Each cycle is an impulse at the specified amplifier impulse current and voltage time histories (see 7.1.1, 7.2.4 and 7.3.4), followed by a 1 min period for the amplifier to cool Repeat the sequence of cycles for a time duration not less than 3t a,s (see 8.2.4) Carry out the test with the amplifier loaded with the load Z a,i (see 7.2.4 and 8.6).
Spill-over limits
When conducting system sine testing with masses, the maximum allowable harmonic current spill-over is limited to 1% of the maximum current below 2,000 Hz Additionally, the maximum harmonic acceleration spill-over should not exceed 10% of the maximum acceleration within the same frequency range These limits are essential unless otherwise specified to ensure accurate and reliable testing results.
For system random or impulse testing with masses m 10 and m 40 , unless otherwise specified, the maximum allowable random current spectral density (impulse current spectrum) spill-over above 2 000 Hz is
where Φ b is the random current spectral density (impulse current spectrum) below 2 000 Hz
For amplifier sine, random and impulse distortion testing with amplifier test loads Z a,s , Z a,r and Z a,i , unless otherwise specified, the maximum allowable current spill-over of any harmonic is 1 % of the maximum current below 2 000 Hz
Distortion tests
Distortion tests are essential for verifying that the system, vibrator, and amplifier can deliver the required performance levels, ensuring they are capable of generating the specified accelerations, currents, and voltages As drive levels increase beyond optimal ranges, distortion rises quickly, making it a key indicator of performance limits Typically, a distortion threshold of 1% to 3% is used to identify the maximum available output, helping to assess system adequacy and prevent overdrive.
Sections 8.5.5 to 8.5.9 employ simplified methods to estimate whether the system and components are adequately sized, utilizing amplifier test loads and simplified waveforms These techniques focus on frequencies or frequency bands that represent typical worst-case conditions, ensuring reliable performance under demanding scenarios.
The distortion of any vibration test system variable, applicable for sinusoidal operation, and with limitation to random and impulse operation as well, is
The root-mean-square (RMS) magnitude of the fundamental component is represented by x1, while x2, x3, x4, , xn denote the RMS magnitudes of the undesired harmonic components All harmonic components of significant magnitude are included in this analysis to ensure comprehensive understanding This approach provides a clear assessment of the harmonic distortion in the system, essential for optimizing electrical performance Accurate measurement of both fundamental and harmonic RMS magnitudes is crucial for effective power quality management and minimizing energy losses.
NOTE 1 Some distortion measuring instruments replace the denominator by the total root-mean-square magnitude of the variable:
Unless the distortion is large, typically 10 % or more, the difference between the two definitions is negligible
Some distortion measuring instruments incorporate hum components into the numerator of the measurement equation, which can include frequencies at the fundamental, sub-multiples, and multiples of the system’s fixed frequencies, such as power and switching frequencies Although these hum components are typically undesired, they are not considered a form of distortion in the traditional sense Therefore, if hum components are of significant magnitude and influence the measurement value, they should be excluded to ensure accurate distortion assessment.
Make sine and random system distortion tests at the specified force after conditioning heat runs to stabilize the temperature of the equipment
Carry out impulse system distortion tests at a specified force on equipment at room temperature, i.e 20° to
Make sine, random and impulse system distortion tests with both test masses m 10 and m 40 The larger of the two distortion measurements is the system distortion
To accurately measure system current distortion, it is essential to account for resonances of the moving element and load that may cause large distortion values If such resonances significantly impact measurements, recording the input signal to the amplifier under rated conditions with the vibrator field turned off can help isolate true distortion levels Repeating the current distortion measurement after disabling the vibrator field allows for a more accurate assessment; if the measured distortion is lower, these results should be used for analysis.
Carry out amplifier sine and random distortion tests at the specified sine and random current after conditioning heat runs to stabilize the temperature of the amplifier
Make amplifier impulse distortion tests at the specified impulse current with the amplifier at room temperature, i.e 20 °C to 40 °C
Distortion tests on the system are used to determine whether the system meets the spill-over limits of 8.4 and avoids undesired excitation in the operating band, typically 20 Hz to 2 000 Hz Distortion tests on the power amplifier with test loads are primarily carried out to predict whether a system using the amplifier will meet the same limits
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For accurate distortion measurements, the harmonic components exceeding 0.3% should be included, while all harmonic components above 1.0% must be reported The amplifier's output voltage must be visually monitored throughout all distortion tests to identify any irregularities If waveform clipping occurs, the specific conditions causing it should be documented to ensure comprehensive analysis and compliance with testing standards.
System sine distortion (d s,s) measures the distortion of acceleration at the top center of the test mass using frequency tracking instrumentation This measurement is conducted over a one-octave-per-minute sweep from the minimum to maximum frequency (f min to f max) The process employs sinusoidal vibration control with sufficient accuracy to ensure that load acceleration does not vary by more than 3% from the specified value, ensuring precise assessment of the system’s distortion characteristics.
System sine distortion should be measured at full specified displacement, velocity and force with the test mass m 40
If, during the sweep test of 8.5.2, the magnitude of any single harmonic of the system sine distortion exceeds
1 % of the maximum acceleration below f max , curves showing the maximum values of the distortion components in the f min to 10 000 Hz band shall be provided
System sine acceleration distortion is a measure of the distortion of the acceleration at the top centre of the test mass, measured as in 8.5.2
Amplifier sine distortion da,s measures the current distortion of the amplifier with load impedance Za,s To accurately assess this distortion, drive the amplifier with a low-distortion sinusoidal signal at frequencies between 200 Hz and 1,000 Hz, ensuring both the specified current and voltage are achieved This testing provides a clear evaluation of the amplifier's performance under optimal conditions.
System random distortion d s,r quantifies the random acceleration distortion at the top center of the test mass, providing a critical measure for system performance This distortion is measured using a narrow-band random output within the frequency range of 200 Hz to 1,000 Hz, ensuring consistent root-mean-square current, root-mean-square voltage, and Gaussian amplitude distribution comparable to the system-specified wide-band random output Utilizing a narrow bandwidth simplifies the measurement process of distortion, enhancing accuracy and repeatability (see 7.2.3).
Amplifier random distortion, denoted as d a,r, quantifies the level of random current distortion associated with the load impedance Z a,r This distortion is measured similarly to the method outlined in section 8.5.6, but it employs the specified root-mean-square (RMS) values of random current and voltage Accurate assessment of amplifier random distortion is essential for evaluating signal integrity and ensuring optimal audio and electronic performance.
System impulse distortion d s,i quantifies the impulse acceleration distortion at the top center of the test mass This measurement is performed using a short gated sinusoidal wave train, typically lasting 1 ms to 10 ms, with the frequency carefully adjusted to match the impulse peak voltage and peak current Utilizing a sine wave simplifies the process of assessing distortion, providing a clear and accurate representation of the system's impulse response.
Amplifier impulse distortion d a,i is a measure of the amplifier impulse output current distortion into the load
Impulse generation
To generate the desired impulse time history, it is essential to use measurements from the actual system and load Accelerating the process involves first measuring the transfer function between the amplifier input and the load acceleration By utilizing this transfer function and the target load acceleration time history, you can accurately calculate the necessary amplifier input time history to produce the desired output acceleration This approach ensures precise control and efficient generation of impulse responses in testing setups.
To verify or improve the amplifier input time history, apply a low-level scaled version of the calculated input signal to the amplifier input and record the resulting acceleration time history This process ensures accurate calibration and reliable measurement for your testing needs.
To ensure accurate impulse testing, analyze the acceleration time history and refine the amplifier input accordingly before applying the full impulse to the load When sourcing the amplifier and vibrator separately, perform initial testing with a test mass of 10 kg to validate acceleration and displacement time histories, recording the driver coil voltage and current simultaneously, then repeat with a 40 kg test mass Conduct full impulse force tests with both masses to verify the vibrator's impulse force capability At the amplifier source, use the 40 kg vibrator data to create an impedance load (Z_a,i) that mimics the vibrator impedance and delivers the same peak voltage, which is essential for confirming the amplifier’s impulse current capability, endurance, and distortion performance If the 10 kg mass better represents the actual load conditions, use its voltage and current data for fabricating the impedance load instead of the 40 kg data.
Note that the vibrator and amplifier impulse performance and the amplifier impulse distortion measurement are unique to this specific impulse acceleration time history
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Electrodynamic vibration generation systems vary between manufacturers to meet diverse user needs When drafting a purchase specification, it is essential to request detailed information from potential suppliers about additional equipment features Manufacturers should provide comprehensive data, covering the characteristics listed in sections A.2 to A.20, to ensure customers make informed decisions and select the best vibration testing solutions.
A.2 Mass of the moving element, m e
The mass, as defined by the manufacturer (see 3.8), plays a crucial role in determining the force produced by the system It includes the moving element structure and, in some cases, incorporates parts of the supporting suspension, connecting leads, and the coolant within the coil conductor and leads This comprehensive definition ensures accurate assessment of the system's dynamics and performance.
When describing the attachment interface of a moving element, it is essential to include detailed information about materials, dimensions, and the precise location(s) of force application points or fastening positions, such as on a test table Providing a dimensioned drawing that indicates whether inserts are raised or flush enhances clarity Additionally, details on mounting torque requirements and the maximum allowable axial load ensure proper installation If safety features, like mechanically fusable inserts, are incorporated to prevent damage from over-length fixing bolts, these mechanisms must be thoroughly described to ensure reliable use and maintenance.
A.4 Flatness of the mounting surface
The allowable deviation from a flat surface shall be specified, either of the test table or of the tops of the raised inserts
The allowable static load shall be stated, both with the force axis vertical and with the force axis horizontal, and how this load affects the allowable travel
This is the resonance frequency of the moving mass on its supporting spring and is typically between 5 Hz and 30 Hz
This is the frequency at which the current in the drive coil is in phase with the voltage, and the electrical impedance is a minimum
A.8 Resonance frequency of the moving system
The lowest frequency above the electrical resonance frequency at which the table acceleration phase shifts by 90° from the drive current is generally above 1,500 Hz This frequency indicates the point where phase differences become significant for system performance Typically, the useful upper limit of the operating frequency range is approximately 1.5 times this lower frequency, ensuring optimal functionality and stability in operation.
A.9 Non-uniformity of axial motion of the test table
This is the variation in vibratory motion across the table surface or between the tops of the raised inserts as a function of frequency
A.10 Transverse motion of the test table
This is measured at the load fixing locations on an unloaded table as a function of frequency
To evaluate the performance of a vibration test system, the manufacturer utilizes a set of masses that are ideally dynamically "dead" (see 3.10) Detailed information about these masses, including their geometry, flatness, materials, and fixing locations, is typically provided to ensure accurate and reliable testing results.
An electrodynamic vibrator inherently generates a stray magnetic field above the moving element table, which can affect testing accuracy It is essential to specify the magnetic field's axial profile in the specimen area when the table is unloaded, detailing how it varies with distance from mounting points Both axial and radial magnetic field components should be described to ensure comprehensive understanding If a degaussing coil is employed, its use and effectiveness must also be clearly stated to account for potential magnetic interference.
In the testing region, the magnetic field should be specified for an unloaded table as an axial function of distance from each mounting point, including both axial and radial components, operating at full rated current across the entire frequency range If an alternating current degaussing coil is used, this must be disclosed, along with any resultant reduction in force or increased amplifier current or voltage Providing this data can be costly and should only be requested if the specimen is sensitive to such magnetic fields.
This article discusses the acceleration noise of an unloaded table or force take-off system operating under normal conditions without drive, with the amplifier, field supply, and cooling system all connected and functioning It emphasizes the importance of separately identifying wide band, random, and periodic components of the noise Additionally, it highlights the need to provide detailed information on the magnitude and time history of acceleration transients caused by internal protection devices and on-off sequencing devices.
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This device supports the vibrator's body, incorporating mechanisms to adjust its orientation from vertical to horizontal with precise positioning stops It also often features locking systems to secure the vibrator body and isolate the system effectively.
When designing a vibrator body isolation system, it is essential to specify the resonant frequencies of the body mass on the isolation springs, both with the force axis oriented horizontally and vertically Proper identification of these frequencies ensures effective vibration control and system stability Including these parameters enhances system performance by preventing resonance and reducing transmitted vibrations.
A.17 Sound pressure level of the emitted acoustic noise
Vibration, hydraulic, and cooling systems must be tested at their full rated acceleration using sinusoidal, random, and impulse methods across the entire vibration generator frequency range Measurements should be conducted in at least four directions, including along the axis, and results must be recorded in one-third-octave acoustic bands The specific test method used should be clearly specified to ensure compliance and repeatability.
This is the stabilized temperature of the unloaded test table under continuous full-force conditions
When planning equipment handling, it is essential to specify the dimensions and mass of all components, along with the necessary services such as electrical power, cooling water, air, exhaust or discharge water, air conditioning, and compressed air A detailed description of all cables, hoses, and special tools required for installation and operation should also be included to ensure smooth setup and maintenance.