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
• For the FR-F840-01160(55K) or lower, connect the surge voltage suppression filter (FR-ASF-H/FR-BMF-H) to the inverter
• For the FR-F840-01800(75K) or higher, connect the sine wave filter (MT-BSL/BSC) to the inverter 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.
• For the details of Pr.72 PWM frequency selection, refer to
set "25" (2.5 kHz) in Pr.72.)
• For the details of the surge voltage suppression filter (FR-ASF-H/FR-BMF-H) and the sine wave filter (MT-BSL/BSC), refer to
the Instruction Manual of each option.
• A surge voltage suppression filter (FR-ASF-H/FR-BMF-H) can be used under V/F control and Advanced magnetic flux vector
A sine wave filter (MT-BSL/BSC) can be used under V/F control. Do not use the filters under different control methods.
3. PRECAUTIONS FOR USE OF THE INVERTER
3.5 Countermeasures against deterioration of the 400 V class motor insulation
Shorter than 50 m
15 (14.5 kHz) or lower
50 to 100 m
9 (9 kHz) or lower
207. (When using an optional sine wave filter (MT-BSL/BSC),
Longer than 100 m
4 (4 kHz) or lower