Pwm Carrier Frequency And Soft-Pwm Control - Mitsubishi Electric FR-E800 Series Instruction Manual

8.15

PWM carrier frequency and Soft-PWM control

The motor sound can be changed.
Pr.
72
PWM frequency selection
E600
240 Soft-PWM operation
E601 selection
260 PWM frequency automatic
E602 switchover
 Changing the PWM carrier frequency (Pr.72)
• The PWM carrier frequency of the inverter can be changed.
• Changing the PWM carrier frequency can be effective for avoiding the resonance frequency of the mechanical system or
motor, as a countermeasure against EMI generated from the inverter, or for reducing leakage current caused by PWM
switching.
• Under Real sensorless vector control, Vector control, and PM sensorless vector control, the following carrier frequencies
are used.
Pr.72 setting
0 to 5
6 to 9
10 to 13
14, 15
*1 The carrier frequency is automatically changed to 2 kHz in the low-speed range (lower than 3 Hz) under Real sensorless vector control, or in the
low-speed range (lower than 10% of the rated motor frequency) under PM sensorless vector control.
NOTE
• The carrier frequency may be automatically lowered in the low-speed range (lower than about 10 Hz) for the ND rating, and
over the entire speed range for the LD rating.
Motor noise increases, but not to the point of failure.
 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.
 PWM carrier frequency automatic reduction function (Pr.260)
• Setting Pr.260 = "10" (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).
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
10
0
184
8. (E) Environment Setting Parameters
8.15 PWM carrier frequency and Soft-PWM control
Initial
Name
value
1
1
10
Carrier frequency (kHz)
2
*1
6
*1
10
*1
14
Pr.570 setting
The carrier frequency will reduce automatically with continuous operation of 85% of the
1 (LD)
inverter rated current or higher.
The carrier frequency will reduce automatically with operation of 170% of the inverter ND
2 (ND)
rated current or higher (only in a low-speed range).
Without carrier frequency automatic reduction (Perform continuous operation with the
1 (LD) carrier frequency set to 2 kHz or lower or with less than 85% of the inverter rated current
for the ND rating.)
2 (ND) Without carrier frequency automatic reduction
Setting range
The PWM carrier frequency can be changed. The setting value
0 to 15 represents the frequency in kHz. Note that "0" indicates 0.7 kHz,
"15" indicates 14.5 kHz.
0 Soft-PWM control disabled.
1 Soft-PWM control enabled.
0 PWM carrier frequency automatic reduction function disabled
10 PWM carrier frequency automatic reduction function enabled
Carrier frequency automatic reduction operation
Description