Countermeasures against deterioration of the 400
V class motor insulation
In the PWM type inverter, a surge voltage attributable to wiring constants is generated at the motor terminals. Especially in a
400 V class motor, the surge voltage may deteriorate the insulation. When the 400 V class motor is driven by the inverter,
consider the following countermeasures:
Countermeasures (with induction motor)
It is recommended to take one of the following countermeasures:
Rectifying the motor insulation and limiting the PWM carrier frequency according to the wiring
For the 400 V class motor, use an insulation-enhanced motor.
• Order a "400 V class inverter-driven insulation-enhanced motor".
• For the dedicated motor such as the constant-torque motor and low-vibration motor, use an "inverter-driven dedicated
• Set Pr.72 PWM frequency selection as indicated below according to the wiring length.
Pr.72 PWM frequency selection
Suppressing the surge voltage on the inverter side
• If the motor capacity is 280 kW or lower, connect the sine wave filter (MT-BSL/BSC) to the output side.
Countermeasures (with PM motor)
When the wiring length exceeds 50 m, set "9" (6 kHz) or less in Pr.72 PWM frequency selection.
• When using an optional sine wave filter (MT-BSL/BSC), set "25" (2.5 kHz) in Pr.72.
• For the details of the sine wave filter (MT-BSL/BSC), refer to the Instruction Manual of each option.
• A sine wave filter (MT-BSL/BSC) can be used under V/F control. Do not use the filters under different control methods.
• The carrier frequency is limited during PM sensorless vector control. (Refer to the FR-A800 Instruction Manual (Detailed).)
3. PRECAUTIONS FOR USE OF THE INVERTER
3.5 Countermeasures against deterioration of the 400 V class motor insulation
100 m or shorter
6 (6 kHz) or lower
Longer than 100 m
4 (4 kHz) or lower