Mitsubishi Electric FR-F820-00077 Instruction Manual page 262

(E) Environment setting parameters
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.)
● When the PWM carrier frequency automatic reduction function is used, the operation with the
carrier frequency set to 3 kHz or higher (Pr. 72 ≥ "3") automatically reduces the carrier frequency
for heavy-load operation as shown below.
Pr. 260 setting
Tab. 5-42:
.
NOTES Reducing the PWM carrier frequency is effective as a countermeasure against EMI from the
inverter or for reducing leakage current, but doing so increases the motor noise.
When the PWM carrier frequency is set to 1 kHz or lower (Pr. 72 ≤ 1), the increase in the harmonic
current causes the fast-response current limit to activate before the stall prevention operation,
which may result in torque shortage. In this case, disable the fast-response current limit in Pr. 156
"Stall prevention operation selection".
Parameters referred to
Pr. 156
Pr. 570
Pr. 800
5 - 90
Pr. 570 setting
1 0 (SLD), 1 (LD)
0 (SLD)
0
1 (LD)
Parameter settings for PWM carrier frequency automatic reduction operation
Stall prevention operation selection
Multiple rating setting
Control method selection
Carrier frequency automatic reduction operation
Continuous operation with the 85% or higher inverter rated current
reduces the carrier frequency automatically.
Continuous operation with the 85% or higher inverter rated current
reduces the carrier frequency automatically.
Without carrier frequency automatic reduction
(Perform continuous operation with the carrier frequency set to 2 kHz or
lower or with less than 85% of the inverter rated current.)
Parameters
=> page 5-180
=> page 5-71
=> page 5-41