Motor Noise, Emi Measures, Mechanical Resonance; Pwm Carrier Frequency And Soft-Pwm Control (Pr. 72, Pr. 240, Pr. 260) - Mitsubishi Electric FR-F720-00046 Instruction Manual

4.15 Motor noise, EMI measures, mechanical resonance

Purpose
Reduction of the motor noise
Measures against EMI and leakage currents
Reduce mechanical resonance

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

You can change the motor sound.
Parameter
Name
Number
72 * PWM frequency selection
Soft-PWM operation
240 *
selection
PWM frequency automatic
260
switchover
The above parameters can be set when Pr. 160 User group read selection = "0". (Refer to page 179.)
* 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 EMI measures or on leakage current reduction caused by the PWM switching.
⋅ When using an option sine wave filter (MT-BSL/BSC) for the FR-F720-03160 (FR-F740-01800) 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 308 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.
Motor noise, EMI measures, mechanical resonance
Parameter that must be Set
Carrier frequency and
Soft-PWM selection
Speed smoothing control
Setting Range
Initial
200V class (400V
Value
class)
02330
(01160) 0 to 15
or less
2
03160
(01800) 0 to 6, 25
or more
0
1
1
0
1
1
Pr. 72, Pr. 240, Pr. 260
Pr. 653, Pr. 654
Description
PWM carrier frequency can be changed. The
setting displayed is in [kHz]. Note that 0 indicates
0.7kHz, 15 indicates 14.5kHz and 25 indicates
2.5kHz.
(25 is exclusively for a sine wave filter.)
Soft-PWM is invalid
" "
When Pr. 72 = "0 to 5" ( 0 to 4
03160 (FR-F740-01800) or more), soft-PWM is
valid.
PWM carrier frequency is constant independently
of load.
When the carrier frequency is set to 3kHz or more
(Pr. 72 ≥ "3"), perform continuous operation at less
than 85% of the rated inverter current.
Decreases PWM carrier frequency automatically
when load increases.
Refer to
Page
159
160
for FR-F720-
4
159