MITSUBISHI ELECTRIC FR-S520 - Manual (Page 184)

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5
.4 Inverter-driven 400V class motor
In the PWM type inverter, a surge voltage attributable to wiring constants is generated
at the motor terminals. Especially for a 400V class motor, the 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 surge voltage on the inverter side
On the secondary side of the inverter, connect the optional surge voltage
suppression filter (FR-ASF-H).