BSI Standards PublicationMechanical structures for electronic equipment — Tests for IEC 60917 and IEC 60297 Part 5: Seismic tests for chassis, subracks and plug-in units... INTRODUCTION
General
The parameters including time history, zero period acceleration, damping ratio, and severities—such as frequency range, required response spectrum, and acceleration per axis—are derived from the methodologies outlined in IEC 60068-3-3, IEC 60068-2-57, and the specifications for environment zone 4 as defined in IEC 60721-2-6.
General conditions
The seismic tests will utilize a synthesized waveform and can be conducted under either single-axis or tri-axis conditions as specified in the standard The duration of the significant portion of the time history is determined from the moment the plot first reaches 25% of its maximum value until it decreases for the final time.
The Test Response Spectrum (TRS) must meet or exceed the Required Response Spectrum (RRS) as illustrated in Figures 1 and 3 for single-axis and tri-axis evaluations, respectively A damping ratio of 3% or 2% is utilized for assessing both the TRS and RRS, excluding the frequency range below 0.5 Hz and above 50 Hz Additionally, the standard acceleration due to gravity (g) is rounded to the nearest whole number.
The test waveform must comply with the Required Response Spectrum (RRS) It is permissible for the Test Response Spectrum (TRS) to be lower than the RRS, particularly in frequency ranges below half or above twice the first natural frequency, but it must not exceed 20% of the RRS Additionally, if the TRS fails to meet the RRS due to the displacement limitations of the vibration table, it must still conform to the requirements at frequencies equal to or greater than 1 Hz.
Single-axis acceleration
The vibration table must have each axis accelerated independently, with acceleration measurements taken during the test as outlined in sections 6.2.7 b) and 6.3.6 b) The strong portion of the time history should last at least 18 seconds, while the zero period acceleration of the input test wave must be set at 16 m/s², following the specifications in Figure 1 Additionally, the time history of the test wave is illustrated in Figure 2.
A cc el er at ion (m /s 2 )
Figure 1 – RRS for the test wave (single-axis acceleration)(damping ratio 2,0 %)
Figure 2 – Time history of the test wave (single-axis acceleration)
Tri-axial acceleration
The vibration table must be accelerated along all three axes simultaneously, with each axis experiencing different levels of acceleration as measured during the tests outlined in sections 6.2.7 b) and 6.3.6 b) The strong portion of the time history should last at least 30 seconds For the input test waveform, the maximum required acceleration is 12 m/s² for horizontal movement and 6 m/s² for vertical movement, as specified in Figure 3 Additionally, examples of the time history for each axis are illustrated in Figure 4.
A cc el er at ion (m /s 2 )
0,1 1 10 100 b) Up-and-down A cc el er at ion (m /s 2 )
Figure 3 – RRS for the test wave (tri-axial acceleration)(damping ratio 3 %)
A cc el er ar tion (m /s 2 ) 8
A cc el er ar tion (m /s 2 ) 8
A cc el er ar tion (m /s 2 )
Figure 4 – Time history of the test wave for each axis (tri-axial acceleration)
Specimen monitoring
The functionality of the chassis, subrack, or plug-in unit must be monitored before and after seismic testing, and optionally during the test, in accordance with IEC 61587-1 and IEC 61587-3 Additionally, the structural and mechanical condition of these components should be verified before and after testing For Low Level Contact Resistance (LLCR) testing, monitoring instrumentation must operate at a rate sufficient to detect intermittent malfunctions, with acceptable malfunctioning times being application-specific.
Seismic simulation
The chassis, subrack, or plug-in unit must undergo vibration tests across three axes: longitudinal, transverse, and vertical, as well as seismic simulation tests using a reference waveform The resultant Test Response Spectrum (TRS) will be evaluated to ensure it meets or exceeds the Required Response Spectrum (RRS) within the frequency range of 1.0 Hz to 50 Hz Additionally, the TRS should not exceed the RRS by more than 30% in the amplified region of 3.0 Hz to 7.0 Hz to avoid over-testing of the components.
6 Test setup and parts to be monitored
General
The seismic testing of the chassis, subrack, or plug-in unit must be conducted under intended use and simulated load conditions This testing aims to evaluate the structural and mechanical integrity of individual components, including a single chassis, subrack, or plug-in unit.
Category A – Plug-in units
General
Plug-in units according to IEC 60917 and IEC 60297 series interface with the subrack or chassis with integrated subrack Plug-in units occupy a corresponding position (also called a
To perform a seismic test on a single plug-in unit, it is essential to replicate the corresponding subrack position and interface conditions in the intended use subrack The guide features of the plug-in unit within the subrack must align with the intended use conditions, including guide width, depth, rigidity, and material.
• The subrack or chassis shall be pre-qualified to Clause 4 of this standard and comply with Category B1, B2, or B3
The plug-in unit being tested must have the appropriate free connector attached for its intended use, while the corresponding fixed connector should be securely connected to the subrack or chassis, in accordance with the specified intended use.
The plug-in unit being tested must be placed in the central slot of the subrack and secured using the designated retention devices, which should be tightened to the specified torque values Refer to Figures 7, 8, and 9 for guidance.
• The subrack or chassis with integrated subrack test fixture shall be rigid, see Figures 7, 8 and 9 The test fixture shall be designed using the practices outlined in IEC 60068-2-47.
Plug-in unit simulated load
The simulated mass of a plug-in unit, as outlined in Clause 4, Categories A1 to A4, encompasses both the mass of the plug-in unit itself and the additional simulated load, reflecting its intended use.
To test a plug-in unit, it must be loaded with a simulated mass that reflects the worst-case scenario, as illustrated in Figure 5 for intended use A (discrete distribution of simulated load) and Figure 6 for intended use B (compact distribution of simulated load).
• The simulated load shall be attached to the plug-in unit PB without loosening during the test
• Single or multiple free connectors shall be placed according to their mechanical and electrical mounting features and according to the intended use of the plug-in unit
• Input and output cable(s) on the plug-in unit front panel shall be attached at their end(s) to the test fixture without loosening during the test
• Intended use plug-in unit covers shall be attached
To secure the plug-in unit within the test chassis or subrack during testing, retention screws must be utilized These screws should be tightened to the specified torque values for optimal performance.
Input/output cable(s) Length 254 mm End attached to the test fixture Simulated load
Intended use plug-in unit covers
Plug-in unit front panel Plug-in unit retention
Figure 5 – Plug-in unit intended use A load distribution (discrete)
Input/output cable(s) Length 254 mm End attached to the test fixture Simulated load
Plug-in unit front panel Plug-in unit retention
Figure 6 – Plug-in unit intended use B load distribution (compact)
Plug-in unit test setup onto the test fixture
The plug-in unit to be tested shall use a 6.2 intended use and pre-qualified subrack or chassis with integral subrack, mounted onto the vibration table using a rigid fixture
Mounting condition is referred to in IEC 60068-2-6, in which there is a reference to IEC 60068-2-47
The test fixture must be designed according to IEC 60068-2-47 standards, ensuring a minimum of 1U (as per IEC 60297) or 1SU (according to IEC 60917) of free space above and below the test specimen, as illustrated in Figures 7 and 8.
• The plug-in unit under test shall be mounted into the centre slot of the intended use chassis or subrack (with worst condition in mind)
• Filler panels (any type or size) shall be attached to close any open slot positions in the pre-qualified subrack or chassis
• The choice of pretested chassis or subrack and filler panels shall comply with the type of plug-in unit under test (non-EMC or EMC)
• The plug-in unit under test and the filler panel retention screws shall be tightened to their recommended torque values
• Input and output cable(s) on the plug-in unit front panel under test shall be attached at their end(s) to the test fixture without loosening during the test
• The test fixture shall have at least 1U (per IEC 60297) or 1SU (per IEC 60917) free space above and below the chassis or subrack to be tested
1U or 1SU min n × U or n × SU
Centre positioned plug-in unit with simulated load under test
I/O cable attachment Subrack pre-qualified per 6.2 IEC 2887/13
Figure 7 – Plug-in unit test setup – Subrack
Centre positioned plug-in unit with simulated load under test
1U or 1SU min n × U or n × SU
Subrack integrated Chassis pre-qualified per 6.2 z x y
Figure 8 – Plug-in unit test setup – Chassis with integrated subrack
Plug-in unit test fixture setup to the vibration table
Mounting condition is referred to in IEC 60068-2-6, in which there is a reference to IEC 60068-2-47
The chassis or subrack test fixture is to be attached to the vibration table via bolts, see Figure
Motor actuator and Vibration table
Acceleration monitor Displacement transducer Subrack/chassis pre-qualified per 6.2
Plug-in unit under test Front panel z y x
Plug-in unit under test
Figure 9 – Block diagram of the plug-in unit test setup
Plug-in unit mechanical parts under test
• Overall mechanical construction of the plug-in unit
• Guidance feature (guide rail) of the subrack
• Subrack retention device of the plug-in unit
• Plug-in unit mechanical hot-swap functionality
• Free connector/fixed connector mechanical reliability according to connector of choice standard or specification
• Free connector/fixed connector electrical (LLCR) reliability (optional) See 6.2.9
• Earth bond continuity See IEC 61587-1
• ESD contact interface to the Subrack See IEC 60297-3-101
• EMC contact mechanical reliability See IEC 61587-3.
Vibration response monitoring
The control accelerometer must be installed on the front panel of the plug-in unit, which should be positioned in the center slot of the subrack Refer to Figures 7, 8, and 9 for visual guidance.
Plug-in unit measurements
The following measurements must be reported: a) the critical frequency and damping ratio of the plug-in unit under test, assessed through sinusoidal or random waveform sweeps before and after the seismic test; b) the acceleration of the vibration table during the test; c) the acceleration of the plug-in unit; and d) the Low Level Contact Resistance (LLCR) as per IEC 60512-2-1, which can be measured before, after, and/or during the test as an optional step.
Test sequence
• Mount the test fixture in one of the three axes to the vibration table
• Attach the vibration monitoring equipment to the plug-in unit per 6.2.6
• Perform a resonance survey in accordance with 5.2
• Plot all accelerometer data in the format of acceleration versus frequency and record resonant frequency(s)
• Verify the plug-in unit structural/mechanical condition
• Verify all securing mounting parts torque and re-torque as necessary
• Perform a seismic simulation in accordance with 5.5 and 5.6
• Plot all accelerometer’s shock response spectra and the time history of the control accelerometer
• Inspect the plug-in unit and record any structural/mechanical or functional non- conformance
• Verify all securing mounting parts torque and re-torque as necessary
• Repeat the above sequence in the two remaining mutual perpendicular axes.
Plug-in unit electrical parts test (free and fixed connector)
This standard focuses solely on mechanical reliability during seismic testing While electrical tests for seismic plug-in units, such as Low Level Contact Resistance (LLCR), are optional, they can be agreed upon by the supplier and user or mandated by specific application requirements Users must specify the parameters for measurement equipment, which should include current, voltage, resistance, and the duration for assessing maximum intermittent or high resistance values.
Acceptance criteria
The plug-in unit and its interface with the test chassis or subrack show no permanent deformation, ensuring the integrity of components like the retention mechanism, ESD interface, EMC interface, guide rail, and hot swap switch function Additionally, there is no visible damage, such as abrasion, to the fixed and free connectors Furthermore, the earth bond continuity remains intact, measuring less than 0.1 Ω in accordance with IEC 61587-1 standards.
Category B – Chassis or subracks
General
Subracks defined by IEC 60297 and IEC 60917 can be integral components of a cabinet or chassis, as illustrated in Figure 10 Additionally, chassis without subracks are also considered part of a cabinet under the IEC 60297 and IEC 60917 standards.
The chassis or subrack under test must be installed in a pre-qualified cabinet that complies with IEC 61587-2 This standard specifies the cabinet position for conducting a generic seismic test on a single chassis or subrack The mounting conditions are determined by the intended use, which includes factors such as the mass of the chassis/subrack, attachment points to the cabinet, and any necessary additional support like support rails or telescopic slides It is essential that the attachment points are secured to the cabinet with the recommended torque values.
To establish a standardized ecosystem, 3 mm aluminum front panels must be utilized and installed in accordance with IEC 60297 or IEC 60917 at the unused mounting positions of the cabinet's front and rear This approach ensures consistency in test reports across various supplier solutions Alternative thicknesses or materials for front panels may be allowed with user agreement It is essential to secure the front panel attachment points to the cabinet by adhering to the recommended torque values.
• Chassis with integrated subracks and subracks shall be assembled with simulated load plug-in units complying with Clause 4, Category A1 to A4 and 6.2.1
• Chassis with integrated subracks and subracks shall be assembled with simulated loads complying with Clause 4, Category B1 to B3
• Chassis (without integrated subracks) shall be assembled with simulated loads complying with Clause 4, Category B1 to B3
Plug-in unit 3 Front panel 1
Cabinet pre-qualified per IEC 61587-2 x z y
1 Front panels according to the IEC 60297 or IEC 60917 series are to be assembled to the front/rear of the cabinet
3 Plug-in unit load boards see 6.2.1
Figure 10 – Chassis or subrack test setup
Chassis or subrack simulated load
Subracks must be designed to accommodate the intended use mass, which should be properly loaded and distributed through the designated plug-in unit categories (A1 to A4) and include the necessary free connector The fixed connector within the subrack must be securely attached according to its intended use Additionally, chassis must also support the mass in alignment with their intended purpose For chassis that incorporate an integrated subrack, they should represent a combination of these requirements.
Chassis or subrack test setup onto the vibration table
Mounting condition is referred to in IEC 60068-2-6, in which there is a reference to IEC 60068-2-47
The chassis or subrack test cabinet is to be attached to the vibration table in compliance with IEC 61587-2, see Figure 11.
Chassis or subrack mechanical parts under test
• Overall mechanical construction of the chassis or subrack
• Guidance feature (guide rail) of the subrack
• Plug-in unit retention device in the subrack
• EMC contact mechanical reliability See IEC 61587-3
• Earth bond continuity See IEC 61587-1.
Vibration response monitoring
• The control accelerometer shall be mounted near one of the specimen mounting bolts
A tri-axial response accelerometer must be installed on the specimen, specifically at the location on its exterior where the highest acceleration levels are anticipated.
Motor actuator and Vibration table
Plug-in unit load boards
Chassis or subrack under test
Chassis or subrack under test
Cabinet pre-qualified per IEC 61587-2 see Figure 8
Figure 11 – Block diagram of the chassis or subrack test setup
Chassis or subrack measurements
The following measurements must be taken and reported: a) the critical frequency and damping ratio of the loaded chassis or subrack, assessed through sinusoidal or random waveform sweeps before and after the seismic test; b) the acceleration of the vibration table during the test; and c) the acceleration of the chassis or subrack.
Test sequence
• Mount the chassis or subrack in one of the three axes to the cabinet on the vibration table
• Attach the vibration monitoring equipment to the chassis or subrack per 6.3.4
• Perform resonance survey in accordance with 5.2
• Plot all accelerometer data in format of acceleration versus frequency and record resonant frequency(s)
• Verify the chassis or subrack structural/mechanical condition
• Verify all securing mounting parts torque and re-torque as necessary
• Perform a seismic simulation in accordance with 5.5 and 5.6
• Plot all accelerometer’s shock response spectra and the time history of the control accelerometer
• Inspect the chassis or subrack and record any structural/mechanical or functional non- conformance
• Verify all securing mounting parts torque and re-torque as necessary
• Repeat the above sequence in the two remaining mutual perpendicular axes.
Acceptance criteria
The chassis and subrack structure, along with their interfaces to the plug-in unit under test, show no permanent deformation, ensuring the integrity of components like the plug-in unit retention, ESD interface, EMC interface, and guide rail Additionally, the test cabinet interface and retention remain undamaged, with no visible wear on the fixed and free connectors Furthermore, the earth bond continuity is maintained at less than 0.1 Ω, in compliance with IEC 61587-1 standards.
Example of test setup reporting
Subrack test setup reporting
The cabinet has been pre-qualified according to IEC 61587-2 standards, ensuring compliance with Test Category B as specified in IEC 61587-5 It falls under Subrack Mass Category B2, also per IEC 61587-5 The plug-in unit is designed to support a load of 12x 7HP, with each unit weighing 5 kg, and the subrack's aperture is theoretically divided into 84 horizontal pitches, where 1 HP equals 5.08 mm For detailed load distribution of the plug-in unit, refer to Figure 6 in accordance with IEC 61587-5.
Plug-in unit test setup reporting
The article discusses a resonance-free (rigid) test fixture compliant with IEC 61587-5 standards It highlights a subrack that has been pre-qualified under IEC 61587-5 category B2 Additionally, it mentions a plug-in unit that falls under mass category A3, with a width of 6HP and a weight of 4 kg, indicating that the subrack's aperture is theoretically subdivided.
84 horizontal pitches, 1 HP=5,08 mm) e) Plug-in unit intended use load distribution per IEC 61587-5, see Figure 5 f) Filler panels 13 × 6HP
ATIS-0600329:2008: Network Equipment – Earthquake Resistance
GR-63-CORE: Network Equipment-Building System (NEBS) Requirements: Physical Protection
NOTE Vibration generators and waveform contact:
• For the synthesized waveform shown in Figure 2 (single axis seismic acceleration test), contact: Telcordia Technologies, Inc
• For the synthesized waveform shown in Figure 4 (tri-axial seismic acceleration test), contact: NTT Facilities, Inc