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 PM motor control, the following carrier frequencies are used.
Pr. 72 setting
0 to 5
6 to 9
10 to 13
In the low-speed range (lower than 10% of the rated motor frequency), the carrier frequency is
automatically changed to 2 kHz.
(For FR-F820-00490(11K) or lower and FR-F840-00250(11K) or lower)
● When using the optional sine wave filter (MT-BSL/BSC), set Pr. 72 = "25" (2.5 kHz).
(FR-F820-03160(75K) or higher, FR-F840-01800(75K).)
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-F820-02330(55K) or lower and FR-F840-01160(55K) or
lower, set Pr. 72 to "5 kHz or less".
To enable it for the FR-F820-03160(75K) or higher and FR-F840-01800(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.
Carrier frequency [kHz]
Carrier frequencies in different control modes
(E) Environment setting parameters
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