Mitsubishi Electric FR-A820-00046 Instruction Manual page 401

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
1
0
Tab. 5-89:
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".
The lower limit of carrier frequency after the reduction under PM sensorless vector control (low-
speed range high-torque characteristic enabled) is 6 kHz.
During fast-response operation, the carrier frequency automatic reduction function is disabled.
Parameters referred to
Pr. 156
Pr. 570
Pr. 788
Pr. 800
FR-A800
Pr. 570
FR-A820-04750(90K) or lower,
setting
FR-A840-02600(90K) or lower
0 (SLD), Continuous operation with the 85% or higher rated inverter current reduces the carrier
1 (LD) frequency automatically.
Operation with the 150% or higher rated
2 (ND),
inverter current for the ND rating reduces the
3 (HD)
carrier frequency automatically.
Continuous operation with the 85% or higher rated inverter current reduces the carrier
0 (SLD)
frequency automatically.
Without carrier frequency automatic reduction
1 (LD)
(Perform continuous operation with the carrier frequency set to 2 kHz or lower or with less than
85% of the rated inverter current.)
2 (ND),
Without carrier frequency automatic reduction
3 (HD)
Parameter settings for PWM carrier frequency automatic reduction operation
Stall prevention operation selection
Multiple rating setting
Low speed range torque characteristic selection
Control method selection
Carrier frequency automatic reduction operation
FR-A840-03250(110K) or higher
Continuous operation with the 85% or higher
rated inverter 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 for the
ND rating.)
(E) Environment setting parameters
=> page 5-84
=> page 5-201
=> page 5-75
=> page 5-56
5 - 221