Mitsubishi Electric FR-F800 Series Instruction Manual page 220

 Soft-PWM control (Pr.240)
• Soft-PWM control is a function that changes the motor noise from a metallic sound into an inoffensive, complex tone.
• Setting Pr.240 = "1" will enable the Soft-PWM control.
• To enable the Soft-PWM control, set Pr.72 to 5 kHz or less for the FR-F820-02330(55K) or lower or the FR-F840-
01160(55K) or lower. For the FR-F820-03160(75K) or higher or the FR-F840-01800(75K) or higher, set Pr.72 to 4 kHz or
less.
NOTE
• 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 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
setting
1
0
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.
Parameters referred to
Pr.156 Stall prevention operation
Pr.570 Multiple rating
Pr.800 Control method
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Pr.570 setting
The carrier frequency will reduce automatically with continuous operation of 85% of the inverter rated
0 (SLD), 1 (LD)
current or higher.
The carrier frequency will reduce automatically with continuous operation of 85% of the inverter rated
0 (SLD)
current or higher.
Without carrier frequency automatic reduction (Perform continuous operation with the carrier frequency
1 (LD)
set to 2 kHz or lower or with less than 85% of the inverter rated current.)
selectionpage 290
settingpage 204
selectionpage 177
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Carrier frequency automatic reduction operation
5. PARAMETERS
5.4 (E) Environment setting parameters
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