Mitsubishi Electric FR-A800 Series Instruction Manual page 359

 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 carrier frequency automatic reduction function is used, 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
Pr.570 setting
setting
0 (SLD), 1 (LD)
1
2 (ND), 3 (HD)
0 (SLD)
1 (LD)
0
2 (ND), 3 (HD)
NOTE
• 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
Pr.570 Multiple rating
Pr.788 Low speed range torque characteristic
Pr.800 Control method
358
5. PARAMETERS
5.7 (E) Environment setting parameters
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FR-A820-04750(90K) or lower, FR-A840-
02600(90K) or lower
The carrier frequency will reduce automatically with continuous operation of 85% of the inverter rated
current or higher.
The carrier frequency will reduce automatically with
operation of 150% of the inverter ND rated current
or higher.
The carrier frequency will reduce automatically with continuous operation of 85% of the inverter rated
current or higher.
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.)
Without carrier frequency automatic reduction
selectionpage 431
settingpage 343
selectionpage 233
selectionpage 221
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Carrier frequency automatic reduction operation
Continuous operation with the 85% or higher
inverter rated current for the ND rating 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.)
FR-A840-03250(110K) or higher