efficiency is the ratio of output power to input power expressed in the same unit, usually expressed as a percentage. the output power is equal to the input power minus the total loss. if two of the three variables (input, total loss or output) are known, the efficiency can be calculated with the following formula 1 or 2:
gb 30253 energy efficiency limit and energy efficiency grade of permanent magnet synchronous motor gb / t 22669 test method for three-phase permanent magnet synchronous motor is used for motor energy efficiency detection.
the input efficiency of asynchronous motor (gb 2262.2) "shall be determined by the input loss method of permanent magnet synchronous motor in gb 2262.69".
the efficiency of permanent magnet synchronous motor for elevator and variable frequency drive permanent magnet synchronous motor shall be determined according to 10.2.1 "direct method input output method (method a)" in gb / t 22670.
1. test method for efficiency of asynchronous starting three-phase permanent magnet synchronous motors - method b
method b - loss analysis method for measuring input-output power requires electric power test instrument and torque speed test instrument to measure and collect relevant parameters.
the accuracy of the electric quantity measuring instrument shall not be lower than grade 0.5. when measuring the motor efficiency with method b, in order to maintain the accuracy and repeatability of the test results, the accuracy level of the instrument is required to be no less than 0.2 (full scale).
the accuracy grade of torque measuring instrument (including dynamometer and sensor) for general test shall not be lower than 0.5. when the efficiency is measured by method b, the accuracy grade of the torque tester shall not be lower than grade 0.2 (full range).
the reading error of tachometer is within ± 1r/minl. the accuracy level of frequency meter shall not be lower than 0.1 (full scale).
method b test is mainly composed of rated load thermal test, load test and no-load test. the thermal test shall be carried out first, which is conducive to the stability of motor friction loss. then the load test shall be carried out, and finally the no-load test shall be carried out. if the test cannot be carried out continuously in the above sequence, the motor must reach the thermal stability state during the rated load thermal test before the load test.
2. controller driven three-phase permanent magnet synchronous motors - method a
method a - input-output method is to calculate the efficiency by using the ratio of measured output power to input power. during the test, the tested motor shall reach the thermal stability state under the rated load for load test, and the efficiency shall be obtained by analyzing and calculating the measured data. the accuracy of a-method input electric power measuring instrument shall not be lower than grade 0.5, and grade 0.2 is preferred for model selection; output mechanical power measurement: use dynamometer or torque and speed sensor to measure the torque and speed of motor, and the accuracy of torque sensor shall not be lower than 0.2.
when the test points of method a are adopted, the input and output power shall be corrected for temperature, and the copper consumption of stator and rotor shall be converted to the ring temperature of 25 ℃; the output power shall be determined by torque correction.