Pwm Carrier Frequency And Soft-Pwm Control - Mitsubishi Electric 800 Series Instruction Manual

7.14

PWM carrier frequency and Soft-PWM control

The motor sound can be changed.
Pr. Name
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 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 Pr.570 setting
1 (LD)
10
2 (ND)
1 (LD)
0
2 (ND)
Initial
Setting range
value
1 0 to 15
0
1
1
0
10
10
Carrier frequency (kHz)
2
*1
6
*1
10
*1
14
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 170% of the inverter ND
rated current or higher (only in a low-speed range).
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
Description
The PWM carrier frequency can be changed. The setting value
represents the frequency in kHz. Note that "0" indicates 0.7 kHz,
"15" indicates 14.5 kHz.
Soft-PWM control disabled.
Soft-PWM control enabled.
PWM carrier frequency automatic reduction function disabled
PWM carrier frequency automatic reduction function enabled
Carrier frequency automatic reduction operation
7. (E) Environment Setting Parameters
7.14 PWM carrier frequency and Soft-PWM control
1
2
3
4
5
6
7
8
9
10
153