Specific test methods for determining losses and efficiency of converter-fed AC motors
IEC 60034-2-3-2020 pdf download.Rotating electrical machines — Part 2-3: Specific test methods for determining losses and efficiency of converter-fed AC motors
Machines electriques tournantes — Partie 2-3: Méthodes d’essai spécifiques pour Ia determination des pertes
et du rendement des moteurs a courant alternatif alimentés par convertisseur.
Internal line filters in digital power meters shall be turned off. Synchronization filters (also known as zero-cross filters) that are not in the signal path may be used.
For power measurement, the three-wattmeter method is preferred. All cables used to transmit measurement signals shall be shielded. It has to be noted, that the cable shield is not routed through the current transducers.
5.1.3 Mechanical output of the motor
The instrumentation used to measure supply frequency shall have an accuracy of ±0,1 % of full scale. The speed measurement should be accurate within 0,1 revolutIon per minute for speeds up to 3 000 min1 and 0,03 % above.
The instrumentation used to measure the torque shall have a minimum class of 0,2 when the rated efficiency is expected to be below 92 %, 0,1 below 95 %and 0,05 or better for higher efficiencies. The minimum torque measured shall be at least 10 % of the torque measurement device’s rated torque. If a better class instrument is used, the allowed torque range can be extended accordingly.
5.2 Converter set-up
5.2.1 General
For all tests using the comparable converter, it should be parameterized according to the requirements of this document or, if a unique combination of converter and motor is to be tested, the converter should be parameterized according to the specific application requirements. The chosen parameter settings shall be recorded in the test report.
5.2.2 Comparable converter set-up for rated voltages up to I kV
The comparable converter has to be understood as a voltage source independent of load current.
It has to be noted, that the so-called comparable converter operating mode is not intended or requested for any commercial application, but it is a typical set-up. The purpose of the comparable converter set-up Is to establish comparable test conditions for motors designed for operation with commercially available converters.
The reference conditions defined below shall only be used for verification of compliance with national energy efficiency regulations, in particular the 90 % speed and 100 % torque load point. For all other purposes including the interpolation procedure according to Annex A preferably the original system configuration should be used.
• Operation at 90 % speed and rated torque with constant rated flux (approx. 90 % of rated voltage) for both induction machines and synchronous machines.
NOTE The raled flux is defined by the rated voltage given on the name plate of the motor. Therefore, a measurement at the 90 % speed and 100 % torque point with rated flux will be fully replicable for regulation authorities
• For motors with a rated speed up to 3 600 min1, the switching frequency shall not be higher than 5 kHz.
• For motors with a rated speed above 3 600 min1, the switching frequency shall not be higher than 10 kHz.
The conductor cross-sectional area of the motor cable should be selected such that the voltage drop is not significant at rated load. An example for a typical test setup can be found in
IEC 61800-9-2:2017.
5.2.3 Testing with converters with rated voltages above I kV
For converters with voltage ratings above 1 kV a generally accepted comparable converter and cable length cannot be specified. Such motors, cables and specific converters can only be tested as a complete power drive system because the pulse patterns of frequency converters for higher output powers vary between manufacturers and differ greatly between no-load and rated load.
5.2.4 Testing with other converters
Motors that are operated with converters that produce a voltage with less harmonic content than in case of supply by the comparable converter, for example multi-level converters or converters with higher switching frequencies, will typically have lower losses compared with measurements made with the comparable converter at 4 kHz or 8 kHz switching frequency. Reference measurements on such motors shall still be performed under the reference conditions as given above. Motor efficiency values measured under non-reference conditions can be provided in the motor documentation.
6 Test method for the determination of the efficiency of converter-fed motors
6.1 Selection of determination method
For the verification of the rated losses and energy efficiency according to energy efficiency classification schemes, the preferred method 6.2 according to Table 1 shall be applied.
The preferred method 2-3-A is mandatory for verification of rated efficiency declared by the manufacturer. This verification may be required by end-users and regulators. For the declaration process and the seven load points according to Annex A the manufacturer is free to use other determination methods also.IEC 60034-2-3-2020 pdf download.