Mitsubishi Electric 700 Series, Instruction Manual

Page: 180 / 416

169
Motor noise, EMI measures, mechanical resonance
4
P
ARA
MET
E
RS
4.15 Motor noise, EMI measures, mechanical resonance
4.15.1 PWM carrier frequency and Soft-PWM control (Pr. 72, Pr. 240, Pr. 260)
(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)
⋅
If continuous operation is performed at 85% or higher of the rated inverter current (the value in the parenthesis on
page
370 ) with Pr.260 = "1 (initial setting)" and Pr.72
≥
"3 (inverter carrier frequency is set to 3kHz is higher)," E.THT
(Inverter overload trip) is likely to occur. To avoid that, the carrier frequency is automatically lowered to as low as
2kHz. (Motor noise increases, but not to the point of 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.
Purpose Parameter that must be Set
Refer to
Page
Reduction of the motor noise
Measures against EMI and leakage currents Carrier frequency and
Soft-PWM selection
Pr. 72, Pr. 240, Pr. 260 169
Reduce mechanical resonance Speed smoothing control
Pr. 653, Pr. 654 170
You can change the motor sound.
Parameter
Number
Name
Initial
Value
Setting Range
200V class (400V
class)
Description
72 * PWM frequency selection 2
02330
(01160)
or less
0 to 15
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.)
03160
(01800)
or more 0 to 6, 25
240 *
Soft-PWM operation
selection
1
0 Soft-PWM is invalid
1
When Pr. 72 = "0 to 5" (
"
0 to 4
"
for FR-F720-
03160 (FR-F740-01800) or more), soft-PWM is
valid.
260
PWM frequency automatic
switchover
1
0
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.
1
Decreases PWM carrier frequency automatically
when load increases.
The above parameters can be set when Pr. 160 User group read selection = "0". (Refer to page 190.)
* 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
.