5.4.18 PWM carrier frequency and Soft-PWM control
The motor sound can be changed.
PWM frequency selection 2
The setting range of the FR-F820-02330(55K) or lower and the FR-F840-01160(55K) or lower
The setting range of the FR-F820-03160(75K) or higher and the FR-F840-01800(75K) or higher
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
• Under PM motor control, the following carrier frequencies are used.
Carrier frequency (kHz)
0 to 5
6 to 9
10 to 13
In the low-speed range (less than 10% of the rated motor frequency), the carrier frequency is automatically changed to 2 kHz
(for the FR-F820-00490(11K) or lower and the FR-F840-00250(11K) or lower).
• When using an optional sine wave filter (MT-BSL/BSC), set "25" (2.5 kHz) in Pr.72 (for the FR-F820-03160(75K) or higher
and FR-F840-01800(75K) or higher).
• In the low-speed range (about 10 Hz or lower), the carrier frequency may be automatically lowered. 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 function 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, set Pr.72 to 5 kHz or less for the FR-F820-02330(55K) or lower or the FR-F840-
01160(55K) or lower. For the FR-F820-03160(75K) or higher or the FR-F840-01800(75K) or higher, set Pr.72 to 4 kHz or
• While a sine wave filter (Pr.72 = "25") is being used, the Soft-PWM control is disabled.
The PWM carrier frequency can be changed. The setting value
0 to 15
represents the frequency in kHz. However, "0" indicates 0.7 kHz, "15"
indicates 14.5 kHz, and "25" indicates 2.5 kHz. (The setting value "25"
0 to 6, 25
is for the sine wave filter only.)
Soft-PWM control disabled.
Soft-PWM control enabled.
PWM carrier frequency automatic reduction function disabled (for the
LD, ND, or HD rating).
PWM carrier frequency automatic reduction function enabled.
5.4 (E) Environment setting parameters