Motor Noise, Noise Reduction; Pwm Carrier Frequency And Soft-Pwm Control (Pr. 72, Pr. 240, Pr. 260) - Mitsubishi Electric F700 Instruction Manual

Motor noise, noise reduction

4.15 Motor noise, noise reduction

4.15.1 PWM carrier frequency and Soft-PWM control (Pr. 72, Pr. 240, Pr. 260)

You can change the motor sound.
Parameter
Number
72 * PWM frequency selection
240 * Soft-PWM operation selection
PWM frequency automatic
260
switchover
The above parameters can be set when Pr. 160 User group read selection = "0". (Refer to page 156.)
* The above parameters allow its setting to be changed during operation in any operation mode even if "0" (initial value) is set in
Pr. 77 Parameter write selection.
(1) PWM carrier frequency changing (Pr. 72)
⋅ You can change the PWM carrier frequency of the inverter.
⋅ Changing the PWM carrier frequency produces an effect on avoiding the resonance frequency of a mechanical
system or motor or on reducing noise or leakage current generated from the inverter.
⋅ When using an option sine wave filter (MT-BSL/BSC) for the 75K or more, set "25"(2.5kHz) in Pr. 72.
(2) Soft-PWM control (Pr. 240)
⋅ Soft-PWM control is a control method that changes the motor noise from a metallic tone into an unoffending
complex tone.
(3) PWM carrier frequency automatic reduction function (Pr. 260)
⋅ When continuous operation is performed at 85% or more of the inverter rated current (the parenthesized value of
the rated output current on page 266 or more) with the carrier frequency of the inverter set to 3kHz or more (Pr. 72 ≥
"3"), the carrier frequency is automatically reduced to 2kHz to protect the output transistor of the inverter. (Motor
noise increases, but it is not a failure)
⋅ When Pr. 260 is set to"0", the carrier frequency becomes constant (Pr. 72 setting) independently of the load, making
the motor sound uniform.
Note that continuous operation should be performed at less than 85% of the inverter rating.
CAUTION
⋅ Decreasing the PWM carrier frequency reduces inverter-generated noise and leakage current, but increases motor
noise.When PWM carrier frequency is set to 1kHz or less (
prevention operation due to increase in harmonic currents depending on the motor, resulting in insufficient torque. In such
case, set fast-response current limit operation invalid using
♦ Parameters referred to ♦
Pr.156 Stall prevention operation selection
142
Initial
Name
Value
2
1
1
Refer to page 73
Setting Range
55K or PWM carrier frequency can be changed.
0 to 15
less The setting displayed is in [kHz]. Note
that 0 indicates 0.7kHz, 15 indicates
75K or
14.5kHz and 25 indicates 2.5kHz.
0 to 6, 25
more
(25 is exclusively for a sine wave filter.)
0 Soft-PWM is invalid
When Pr. 72 = "0 to 5" (
1
more), soft-PWM is valid.
PWM carrier frequency is constant
independently of load.
When the carrier frequency is set to
0
3kHz or more (Pr. 72 ≥ "3"), perform
continuous operation at less than 85% of
the rated inverter current.
Decreases PWM carrier frequency
1
automatically when load increases.
≤1), fast response current limit may function prior to stall
Pr.72
Pr.156
Stall prevention operation selection
Description
" "
0 to 4 for 75K or
.