• 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 Real sensorless vector control, vector control, and PM sensorless vector control, the following carrier frequencies
(For the control method and fast-response mode selection, refer to Pr.800 Control method selection on
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 an optional sine wave filter (MT-BSL/BSC), set "25" (2.5 kHz) in Pr.72. (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 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 control method that changes the motor noise from a metallic sound into an inoffensive, complex
• 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 the 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 the 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.
PWM carrier frequency automatic reduction function (Pr.260)
• Setting Pr.260 = "1 (initial value)" will enable the PWM carrier frequency auto-reduction function. If a heavy load is
continuously applied while the inverter carrier frequency is set to 3 kHz or higher (Pr.72 ≥ "3"), the carrier frequency is
automatically reduced to prevent occurrence of the inverter overload trip (electronic thermal O/L relay function) (E.THT).
The carrier frequency is reduced to as low as 2 kHz. Motor noise increases, but not to the point of failure.
5.7 (E) Environment setting parameters
Real sensorless vector control,
Carrier frequency (kHz)
PM sensorless vector control