Mitsubishi Electric Freqrol-A100 Instruction Manual page 188

6.2 DRIVING A 400V CLASS MOTOR WITH THE INVERTER
<n a PWM type inverter, a micro surge voltage attributable to a wiring
is generated at the motor terminals.
Especially for a 400V class motor, the micro surge voltage may deteriorate
the insulation.
When the 400V class motor is driven by the inverter, consider the following measures:
Measures
It is recommended to take either of the following measures:
(1) Rectifying the motor insulation
For the 400V class motor, use an insulation-rectified motor. Specifically,
1) Specify the "400V class inverter-driven, insulation-rectified motor".
2) For the dedicated motor such as the constant-torque motor and low-vibration motor, use the
"inverter-driven, dedicated motor".
(2)
Suppressing the micro surge voltage on the inverter side
On the secondary side of the inverter, connect a filter which suppresses the micro surge voltage
to make the terminal voltage of the motor 850V or less.
When the motor is to be driven by Mitsubishi inverter, connect the optional surge voltage
suppressing filter (see page 191) on the secondary side of the inverter.