IEC/TS 60034 2 3 Edition 1 0 2013 11 TECHNICAL SPECIFICATION SPÉCIFICATION TECHNIQUE Rotating electrical machines – Part 2 3 Specific test methods for determining losses and efficiency of converter fe[.]
Instrumentation
General
In the case of AC machines, unless otherwise stated in this technical specification, the arithmetic average of the three line currents and voltages shall be used
When testing electric motors under load, it is common to encounter fluctuations in output power and other measured quantities To ensure accurate efficiency determination, multiple measurements should be taken at each load point over a period of approximately 30 seconds, with the average of these values used for analysis.
When selecting measuring equipment for converters that supply AC motors, it is essential to consider the harmonics and their impact on motor losses The equipment must be chosen based on the relevant frequency range and should provide sufficient accuracy to ensure reliable measurements.
For temperature measurements a thermo-sensor installed in the hot-spot may be optionally used, as described in IEC 60034-2-1:2007.
Power analyzer and transducers
The instrumentation used for measuring power and current at the motor's input must primarily comply with IEC 60034-2-1:2007 standards However, due to the presence of higher frequency components, additional requirements must also be fulfilled.
The nominal accuracy of the power meters shall be 0,2 % or better at 50 Hz/60 Hz and 0,5 % up to a frequency f r of at least: f r = 10 × f sw for PWM converter output
The measurement range shall be chosen adequately in relation to the measured currents and voltages
For optimal performance, it is recommended to connect current and voltage directly to the power analyser If an external current transducer is necessary, avoid using conventional current transformers; instead, utilize wide bandwidth shunts or zero-flux transducers.
The bandwidth of the current sensors and acquisition channels shall range at least from 0 Hz to 100 kHz
Internal filters in digital power meters shall be turned off
For accurate power measurement, the three-wattmeter method is preferred While the two-wattmeter method (Aaron-connection) is also acceptable, it is important to recognize that not all equipment can effectively compensate for potential errors associated with this method Users should verify this capability by consulting the manufacturer's data sheets.
All cables used to transmit measurement signals shall be shielded.
Mechanical output of the motor
The instrumentation for measuring torque and speed at the motor's output shall meet the requirements of IEC 60034-2-1:2007.
Converter set up
General
All test methods utilizing the test converter must be parameterized in accordance with the specifications outlined, or tailored specifically for a unique combination of converter and motor being tested It is essential to document the selected parameter settings in the test report.
Test converter set up for rated voltages up to 1 kV
The test converter has to be understood as a voltage source independent of load current, set at rated voltage and fundamental frequency (50 Hz or 60 Hz) of the motor under test
The test converter operating mode is specifically designed for establishing comparable test conditions for motors intended for use with commercially available converters, and it is not meant for any commercial applications.
The following reference conditions are defined:
• Two level voltage source converter
• No motor current feedback control activated (to be deactivated, if necessary)
• “Slip compensation” shall not be applied
• No additional components influencing output voltage or output current shall be installed between the test converter and the motor, except those required for the measuring instruments
The fundamental motor voltage must match the rated motor voltage (\$U_{Mot} = U_{N}\$) at frequencies of 50 Hz or 60 Hz To ensure the rated motor voltage is applied without causing overmodulation, the input voltage of the test converter should be set appropriately, but it should not exceed the minimum required level to achieve this condition.
• Fundamental motor frequency equal to rated motor frequency f Mot = f N (50 Hz, 60 Hz)
• Switching frequency f SW = 4 kHz for rated output powers up to 90 kW
• Switching frequency f SW = 2 kHz for output powers above 90 kW
Annex A defines the test converter output stage and establishes test methods to check its conformity The test converter can be fed by an appropriate AC or DC input
A shielded cable shall connect the test converter to the motor The cable length shall be less than 100 m The cable size shall be selected according to the motor rating.
Testing with the converter for the final application
For voltage ratings exceeding 1 kV, it is not feasible to define a standard test converter and cable length Instead, testing must be conducted on the entire power drive system, as the pulse patterns of frequency converters for higher output powers vary significantly among manufacturers and differ markedly between no-load and rated load conditions.
6 Test methods for the determination of the efficiency of converter-fed motors
Test method (see Table 1)
Ref Method Description Subclause Required facility
Harmonic loss determination with test- converter according to Annex A
6.2 Sinusoidal supply and test converter supply for full-load operation
Supply with specific converter for final application
Harmonic loss determination with converter for final application
6.3 Sinusoidal supply and specific converter supply for full-load operation
2-3-C Input-output Torque measurement 6.4 Dynamometer for full-load; specific converter supply 2-3-D Calorimetric Loss determination from coolant temperature rise
Method 2-3-A: Summation of losses with test converter supply
General
Voltage source converters exhibit increased harmonic motor losses with higher loads, even when their output voltage and pulse pattern remain independent of the load In low voltage converters, a constant pulse pattern is typically maintained until the voltage modulation amplitude approaches the limits of the intermediate circuit voltage.
The total additional loss due to converter supply can be calculated by comparing the results of a load test conducted at fundamental frequency supply with those from a load test at converter supply The additional harmonic loss is identified as the difference between the measured losses from these two tests.
A sinusoidal voltage source according to IEC 61000-2-4, class 1, shall be available in addition to the converter to perform these tests (nominally sinusoidal power supply)
The tests utilize a standardized test converter as outlined in Annex A, enabling a consistent comparison of efficiency figures across various machines due to its fixed pulse pattern In contrast, a specific converter with a unique control mechanism, as detailed in method 2-3-B, results in output voltage variations that depend on the manufacturer's specific control schemes.
Test procedure
The sequence of tests is as follows:
• Perform a load test with sinusoidal power supply of rated frequency and rated voltage according to IEC 60034-2-1:2007, method 2-1-1B, 6.1.2.1.1 for the determination of the total losses P Tsin
• Determine the load losses according to IEC 60034-2-1:2007, method 2-1-1B, 6.1.2.1.2
• Perform a load curve test with sinusoidal power supply of rated frequency and rated voltage according to IEC 60034-2-1:2007, method 2-1-1B, 6.1.2.1.3 and determine the losses accordingly
• Perform a no-load test with sinusoidal power supply of rated frequency and rated voltage according to IEC 60034-2-1:2007, method 2-1-1B, 6.1.2.1.4
• Determine the constant losses P C at sinusoidal power supply according to IEC 60034-2-
• Perform a load curve test with test converter supply of rated frequency and rated voltage according to IEC 60034-2-1:2007, method 2-1-1B, 6.1.2.1.3 and determine the losses accordingly
• Perform a no-load test with test converter supply of rated frequency and rated voltage according to IEC 60034-2-1:2007, method 2-1-1B, 6.1.2.1.4
• Determine the constant losses P CC at test converter supply according to IEC 60034-2-
Load-dependent additional harmonic losses – Residual losses P LL and P LLC
Based on the above mentioned tests, the residual losses shall be determined according to
Residual losses at each load point are calculated by deducting the output power, uncorrected stator winding losses at test resistance, iron losses, windage and friction losses, and uncorrected rotor winding losses based on the determined slip value from the input power.
This has to be done for sinusoidal power supply fw fe r s 2 1
P = − − − − − and test converter supply fw fe r s 2C 1C
P LrC to be determined for the same load points as P Lr
= 1 are the corrected friction and windage losses according to IEC 60034-2-1:2007
Residual loss data will be smoothed using linear regression analysis, following IEC 60034-2-1 standards, by expressing the losses as a function of the square of the load torque.
When the slope constants A and A C are established, a value of additional load losses for rated load point shall be determined for sinusoidal and converter supply respectively by using the formulas:
The additional load losses P LLC now encompass all load-dependent losses, including those arising from the fundamental load current and the load-dependent component associated with the harmonics of the test converter.
The difference between the additional load losses for operation with the test converter and with a sinusoidal power supply gives the load-dependent part of the additional harmonic motor losses:
Constant additional harmonic losses – Constant losses P C and P CC
The difference between the no-load losses for operation with the test converter P CC and with a sinusoidal power supply P C is the constant part of the additional harmonic motor losses:
Efficiency determination
The difference between the additional load losses for operation with the test converter and with a sinusoidal power supply are the additional harmonic motor losses
To determine motor efficiency during frequency converter operation, the additional harmonic motor losses must be combined with the fundamental motor losses, as established by IEC 60034-2-1:2007, method 2-1-1B, using a sinusoidal power supply.
The efficiency at test converter supply is determined from converter - test T 2
The harmonic loss ratio is given by
It should be rounded to a full (integer) number.
Method 2-3-B: Summation of losses with specific converter supply
The total additional loss from converter supply is assessed through a load test at the fundamental frequency and another at the converter supply using the designated converter for the application The testing procedure mirrors method 2-3-A, aside from the use of the specific converter system.
Method 2-3-C: Input-output method
Test set-up
The mechanical power \( P_{2C} \) of a machine is assessed through the measurement of shaft torque and speed, while the electrical power \( P_{1C} \) of the stator is recorded during the same testing procedure.
Test procedure
Testing will be performed using the designated converter and a fully assembled motor, ensuring that all necessary components are in place to achieve test conditions that closely resemble normal operating conditions.
Connect the motor being tested to a dynamometer load machine Run the machine at its rated torque until thermal equilibrium is achieved, indicated by a temperature change of 1 K or less over a half-hour period.
At the end of the test, record:
P 1C Input power at specific converter supply
Efficiency determination
Method 2-3-D: Calorimetric method
Efficiency can be assessed through calorimetric measurements of total losses in the tested equipment within the primary or secondary water cooling circuit, following the test procedures outlined in IEC 60034-2-2.
When motor ratings surpass available testing capabilities, calculating additional harmonic losses from converter operation can provide an estimate of these losses This calculation should utilize the actual pulse patterns of the converter, the frequency-dependent equivalent circuit parameters of the electric motor, and motor models that account for harmonic effects.
Definition of the output voltage of the test converter
Definitions and schematic
For the purposes of this part of the document, the following terms and definitions apply in addition to Clause 4
U d ,U d+ ,U d– DC link voltages of the converter section U d+ means the voltage of the positive rail, U d– the potential of the negative rail with reference to NP
U U , U V , U W Phase to NP voltages at the inverter output; block shaped in steady state operation
U* U , U* V , U* W Set-points of the phase to NP voltages at the inverter output
U UD , U VD , U WD Phase to starpoint voltages at the inverter output; block shaped in steady state operation
U* UD , U* VD , U* WD Set-points of the phase to starpoint voltages; sinusoidal in steady state operation
U CCM Common mode voltage related to the star point of the motor
The amplitude of the phase voltages of the motor, denoted as \$U_{ref}\$, remains constant during steady-state operation Similarly, the frequency set-point of the motor voltage, represented as \$f_{1ref}\$, is also constant in this steady-state condition.
U* ext Linearity extension voltage Common mode voltage used in the modulator
S U , S V , S W Switching commands for the inverter phases
Figure A.1 shows star-connected motor, nevertheless the technical specification can also be applied to delta-connected motors with internal or external star-points
The inverter's output voltage, represented as \$U_U\$, \$U_V\$, and \$U_W\$, can be categorized into two types: the differential mode voltage system, also referred to as the symmetrical voltage system (\$U_{UD}\$, \$U_{VD}\$, \$U_{WD}\$), and the common mode voltage relative to the converter's reference point (\$U_{CCM}\$).
The differential mode voltage represents the voltages across the three motor phases, calculated by subtracting the common mode voltage from the inverter output voltage for each phase.
The common mode voltage can be calculated as follows:
Voltage reference and generation of output voltage waveform
This clause describes a method to realize the pulse pattern of the test inverter and it explains, why the measurements should look like shown in Figure A.3
A basic controller generates the set points of the absolute value of the desired motor voltage and the motor frequency U ref , f 1 ref for steady state operation
The sinusoidal voltage set points (U* UD , U* VD , U* WD ) to be applied to the motor are computed in the converter controller
A linearity extension signal, denoted as U* ext, is applied to all voltage set points to enhance the voltage range This common mode voltage ensures that the motor voltage aligns with the set point while minimizing low order harmonics.
Finally these signals are compared to a switching triangle to compute the pulse pattern S u , S v ,
S w The switching triangle is a periodic symmetrical triangle waveform, the frequency of which defines the switching frequency of the inverter The inverter generates the output voltages
(U U , U V , U W ) according to the pulse pattern The block diagram in Figure A.2 describes the system
Figure A.2 – Functional schematic for voltage generation system
The linearity extension signal \( U^*_{\text{ext}} \) for the test inverter is defined as half of the medium of the three sinusoidal voltage set points \( U^*_{\text{UD}} \), \( U^*_{\text{VD}} \), and \( U^*_{\text{WD}} \) The medium voltage is identified as the one with the lowest absolute value, as illustrated in Figure A.3 below.
Figure A.3 – Sinusoidal voltage set point and linearity extension voltage
The sinusoidal voltage set point and the resulting reference voltage to be compared to the switching triangle are shown Figure A.4 for phase U:
Figure A.4 – Voltage set point and extended reference voltage
The inverter's output voltage, measured between the inverter terminal and NP, reflects the pattern formed by comparing the extended reference voltage with the switching triangle This relationship is illustrated in Figures A.5 and A.6, showcasing a fundamental frequency of 50 Hz alongside a switching triangle frequency of 4 kHz.
Figure A.5 – Pulse pattern of motor terminal voltage (fundamental frequency 50 Hz; switching triangle frequency 4 kHz)
Figure A.6 – Magnification of marked area of Figure A.5
The distance between the centers of any two adjacent blocks is the reciprocal value of the switching triangle frequency which is identical with the switching frequency of the inverter.
Checking in the time domain
To check the correct pattern of voltage and frequency applied to the motor, a measurement shall be done at the operation point defined in 5.2.2
The terminal voltage \( U \) of the inverter is illustrated in Figures A.5 and A.6, ensuring that no pulse is absent For a switching frequency of 4 kHz, the distance between the centers of two adjacent blocks is 0.25 ms, while for a switching frequency of 2 kHz, this distance is 0.5 ms.
If there are missing pulses, the DC link voltage shall be increased
To check whether the linearity extension is correctly applied, the terminal voltage U U shall be measured through a low pass filter Figure A.7 shows how the signal should look like
Figure A.7 – Filtered inverter terminal voltage (fundamental frequency of 50 Hz; 2 nd order low pass filter 500 Hz / 0,7)
Only the shape form with double extrema is specific, the signal shall not show any sign of saturation such as a flat segment at the top or at the bottom
Alternatively the terminal voltage may be measured with respect to the positive or the negative DC rail potential, resulting in an offset of –/+U d /2
The earth potential is not suitable as reference potential
IEC/TS 60034-25, Rotating electrical machines – Part 25: Guidance for the design and performance of a.c motors specifically designed for converter supply
IEC 61800-2, Adjustable speed electrical power drive systems – Part 2: General requirements
– Rating specifications for low voltage adjustable frequency a.c power drive systems
IEC 61800-4, Adjustable speed electrical power drive systems – Part 4: General requirements
– Rating specifications for high voltage adjustable frequency a.c power drive systems above
5.1.2 Analyseur de puissance et transducteurs 31
5.2.2 Configuration du convertisseur de référence pour des tensions assignées jusqu’à 1 kV 31 5.2.3 Essais avec le convertisseur destiné à l'application finale 32
6 Méthodes d’essai pour la détermination du rendement des moteurs alimentés par convertisseur 33
6.2 Méthode 2-3-A: Sommation des pertes avec alimentation du convertisseur de référence 33
6.3 Méthode 2-3-B: Sommation des pertes avec alimentation par le convertisseur spécifique 36
Annexe A (informative) Définition de la tension de sortie du convertisseur de référence 38
A.2 Référence de tension et génération de forme d'onde de la tension de sortie 39
A.3 Vérification dans le domaine temporel 42
Figure A.1 – Schéma relatif à un PDS 38
Figure A.2 – Schéma fonctionnel du système de génération de tension 40
Figure A.3 – Point de consigne de tension sinusọdale et tension d’extension de linéarité 40
Figure A.4 – Point de consigne de tension et tension de référence étendue 41
Figure A.5 – Séquence d’impulsions de tension aux bornes du moteur (fréquence fondamentale 50 Hz; fréquence du triangle de commutation 4 kHz) 41
Figure A.6 – Grossissement de la zone marquée de la Figure A.5 42
Figure A.7 – Tension aux bornes de l’onduleur filtrée (fréquence fondamentale de
50 Hz; filtre passe-bas du 2 ème ordre 500 Hz/0,7) 42
Partie 2-3: Méthodes d'essai spécifiques pour la détermination des pertes et du rendement des moteurs à induction en courant alternatif alimentés par convertisseur
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The purpose of this specification is to outline testing methods for determining additional harmonic losses in induction motors powered by converters These losses occur in addition to the losses identified under sinusoidal supply, as defined by IEC 60034-2-1 methods The results obtained from this specification enable the comparison of harmonic losses across various alternating current induction motors powered by converters.
Dans les systốmes d’entraợnement ộlectriques de puissance (PDS: power-drive systems), le moteur et le convertisseur de fréquence sont souvent fabriqués par différents fournisseurs
Motors of the same design are produced in large quantities, with some operating from the grid and others from various types of frequency converters Individual settings of these converters, such as switching frequency and DC bus voltage level, can significantly impact system efficiency It is unrealistic to determine additional harmonic losses for each combination of motor, frequency converter, cable, output filter, and parameter settings Given the challenges in specifying the efficiency of motors powered by converters, this specification outlines a limited number of approaches based on voltage levels and the assigned characteristics of the tested machine.
The procedures outlined in this specification yield a unique value, the harmonic loss ratio \( r_{HL} \), which represents the additional harmonic losses of the motor compared to the motor losses measured under nominal sinusoidal voltage supply.