Mitsubishi Electric FR-A800, Instruction Manual

Page: 401 / 1042

Parameters (E) Environment setting parameters
FR-A800 5 - 221
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
Pr. 570
setting
Carrier frequency automatic reduction operation
FR-A820-04750(90K) or lower,
FR-A840-02600(90K) or lower
FR-A840-03250(110K) or higher
1
0 (SLD),
1 (LD)
Continuous operation with the 85% or higher rated inverter current reduces the carrier
frequency automatically.
2 (ND),
3 (HD)
Operation with the 150% or higher rated
inverter current for the ND rating reduces the
carrier frequency automatically. Continuous operation with the 85% or higher
rated inverter current reduces the carrier
frequency automatically.
0
0 (SLD)
Continuous operation with the 85% or higher rated inverter current reduces the carrier
frequency automatically.
1 (LD)
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 rated inverter current.)
2 (ND),
3 (HD)
Without carrier frequency automatic reduction
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.)
Tab. 5-89: Parameter settings for PWM carrier frequency automatic reduction operation
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 Stall prevention operation selection => page 5-84
Pr. 570 Multiple rating setting => page 5-201
Pr. 788 Low speed range torque characteristic selection => page 5-75
Pr. 800 Control method selection => page 5-56