Countermeasures Against Deterioration Of The 400 V Class Motor Insulation - Mitsubishi Electric FR-A820-00046 Instruction Manual

Precautions for use of the inverter
3.5 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
length
For the 400 V class motor, use an insulation-enhanced motor. Specifically:
– 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 motor".
– Set Pr. 72 "PWM frequency selection" as indicated below according to the wiring length.
Pr. 72 "PWM frequency selection"
Tab. 3-13:
● Suppressing the surge voltage on the inverter side
– For the FR-A840-01800(55K) or lower, connect the surge voltage suppression filter (FR-ASF-H/
FR-BMF-H) to the output side.
– For the FR-A840-02160(75K) or higher, 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".
NOTES For the details of Pr. 72 "PWM frequency selection", refer to page 5-219. (When using an optional
sine wave filter (MT-BSL/BSC), 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 control.
A sine wave filter (MT-BSL/BSC) can be used under V/F control. Do not use the filters under differ-
ent control modes.
The carrier frequency is limited during PM sensorless vector control. (Refer to page 5-219.)
FR-A800

Countermeasures against deterioration of the 400 V class motor insulation

50 m or shorter
Setting of Pr. 72 according to the wiring length
Wiring length
50 m to 100 m
15 (14.5 kHz) 9 (9 kHz)
Longer than 100 m
4 (4 kHz)
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