(E) Environment setting parameters
Changing the PWM carrier frequency (Pr. 72)
● The PWM carrier frequency of the inverter can be changed.
● Changing the PWM carrier frequency can be effective for avoiding the resonance frequency of
the mechanical system or motor, as a countermeasure against EMI generated from the inverter,
or for reducing leakage current caused by PWM switching.
● Under Real sensorless vector control, vector control, and PM sensorless vector control, the follow-
ing carrier frequencies are used. (For the control method and fast-response mode selection, refer
to Pr. 800 "Control method selection" page 5-56.)
Pr. 72 setting
0 to 5
6 to 9
10 to 13
When low-speed range high-torque characteristic is disabled (Pr. 788 = "0"), 2 kHz is used.
In the low-speed range (3 Hz or lower) under Real sensorless vector control, the carrier frequency
is automatically changed to 2 kHz.
(For FR-A820-00490(7.5K) or lower and FR-A840-00250(7.5K) or lower)
● When using the optional sine wave filter (MT-BSL/BSC), set Pr. 72 = "25" (2.5 kHz).
(FR-A820-03800(75K) or higher, FR-A840-02160(75K) or higher.)
In the low-speed range (about 10 Hz or lower), the carrier frequency may be automatically low-
ered. Motor noise increases, but not to the point of failure.
When Pr. 72 = "25", the following limitations apply.
● V/F control is forcibly set.
● Soft-PWM control is disabled.
● The maximum output frequency is 60 Hz.
Soft-PWM control (Pr. 240)
● Soft-PWM control is a control method that changes the motor noise from a metallic sound into
an inoffensive, complex tone.
● Setting Pr. 240 = "1" will enable the Soft-PWM control.
● To enable the Soft-PWM control for the FR-A820-03160(55K) or lower and FR-A840-01800(55K) or
lower, set Pr. 72 to "5 kHz or less".
To enable it for the FR-A820-03800(75K) or higher and FR-A840-02160(75K) or higher, set Pr. 72 to
"4 kHz or less".
While a sine wave filter (Pr. 72 = "25") is being used, the Soft-PWM control is disabled.
5 - 220
Real sensorless vector control,
Carrier frequencies in different control modes
Carrier frequency (kHz)
PM sensorless vector control