Is it good of the VFD brings high DV/DT to the motor?

Introduction of power electronics makes the motors vulnerable to harmonics is a known fact. The presence of common mode voltages decorates the life of the bearing. If the problem is severe, playing with the common voltages using SVPWM in multi level inverters is advantageous. Recently I have witnessed the similar phenomenon in our DFIG based systems. However get rid by changing the switching frequency as it offers high capacitive reactance for this responsible harmonic current. Also by changing the bearings possesses high reactance value. Luckily the stator inductance acts as a pass filter for these harmonic currents. LC is also a preferable solution.

Driving the motor with sinusoidal voltages conveniently eliminates the issue of dv/dt related problems, voltage doubling effects and common mode currents flowing into the motor. The motor-side inverter of the variable frequency drive would have an LC-filter, and the capacitor voltage is a controlled sinusoid. However, the downside would be additional complexity in control, as the inverter would see a third-order LCL filter at the motor end; and also motor terminal voltages need to be controlled to a sinusoid, apart from the conventional vector-controlled quantities.

In addition to the harmonics and harmonic heating, reflected waves can also be an issue in using inverter drives. Since the peak of a reflected wave is almost 2x bus voltage, this has the potential to degrade winding insulation. I believe with some very high dv/dt drives the phenomena can occur with motor leads as short as 10m. Mitigation works best at the motor end, since the reflected waves occur there. This involves filters or other devices to suppress the reflected waves. Mitigation can occur at the inverter, usually in the form of output filtering that slows the rise of the output voltage pulses.