![]() ![]() ![]() Another aspect is the transmission of noise caused by the frequency switching from the motor to the choke. At the output of the du/dt choke we should get a perfectly sinusoidal signal. These chokes also reduce the propagation of electromagnetic disturbances. In addition, they allow to increase the motor main cable length from 30 up to 100 meters depending on the switching frequency. This feature increases the life time of the device by protecting the isolation from damage, reducing operating temperature and reducing motor noise. The task of chokes du/dt is to limit the steepness of voltage rise. How to mitigate effects of the too high voltage rise steepness dV/dtĪ tried and tested way to limit the du/dt parameter is to use filter chokes. In motors designed to operate with VFDs, the permissible values are several dozen percent higher, hence it is worth to specify insulation dedicated for VFDs, when sending an order to the vendor of the electric motors. The insulation of motors with a rated voltage of 400 V is not significantly impaired if the maximum voltage Umax < 1000 V and the steepness of the voltage du/dt < 500 V/μs. fThe total 3 Phase motor/VFD upgrade cost was about 315. The fan blows air up through the VFD and out a passive vent on the top of the box. Fluke virtual demos and product selectorsīoth the maximum value of the voltage pulse and the rise steepness (dV/dt) are dangerous for the motor insulation. The box contains the VFD, the original contactor, a terminal strip, a wall wart for the tachometer, and the optional fan. ![]()
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