Is there a problem with the inverter current detection circuit that will cause the motor to run jitter?
Fault phenomenon: a special frequency converter for 24kw Fuji elevator. The fault is that the elevator starts and stops with severe vibration, and the relative vibration is lighter during operation.
Fault Detection: it is normal to check the drive of the frequency converter, and it is also normal to test the drive capability of the six pipes in the module with low voltage 40v and 10 amperes current, when I checked the current detection circuit, I found that the A7840 on the board was abnormal. I suspected that there was an aging phenomenon. The fault was that I input 100 millivolts and the output was only 0.
234 v, while the normal A7840 has an output voltage of 0 at 100 mV input. About 79 v.
Fault Analysis: If the current detection fails, that is, the voltage after the current detection has a large deviation, this voltage enters the cpu post-processing, which will affect the frequency of the final six output pulses of the inverter, the voltage obtained by current sampling also participates in the calculation after entering the cpu, which eventually affects the output pulses of six channels, thus causing the motor to shake.