Mitsubishi Electric FR-A800, Instruction Manual

Page: 141 / 1042

Precautions for use of the inverter Countermeasures against deterioration of the 400 V class motor insulation
FR-A800 3 - 19
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.
●
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".
Wiring length
50 m or shorter 50 m to 100 m Longer than 100 m
Pr. 72 "PWM frequency selection" 15 (14.5 kHz) 9 (9 kHz) 4 (4 kHz)
Tab. 3-13: Setting of Pr. 72 according to the wiring length
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.)