  This article studies the possibility of controlling the surge impedance of
the electric motor in motor drives. The existing solution to suppress (or
eliminate) the reflected wave impact on the motor insulation run by a Si-IGBT
or SiC-MOSFET-based drive is to use either a sinewave filter or dv/dt filter.
The alternative solution suggested in this article is to implement a
high-bandwidth electronic circuit at the end of the cable or at the motor
terminals to match the surge impedance of the cable and motor. The
high-frequency voltage ringing due to the reflected waves in motor drives is
around 1 MHz, depending on the cable parameters and the length of the cable. In
the proposed method, the electronic circuit can quickly detect the dv/dt rise
and fall edges and adjust the electronic circuit equivalent impedance when
pulses arrive the motor terminals. Thus, the cable and motor surge impedances
can be matched over a short time to prevent reflected waves. As a result, the
leakage currents passing through the ball bearing and overvoltage stress on the
motor insulation can be suppressed significantly.
