Mitsubishi Electric FR-F700PJ Series, Instruction Manual

Page: 186 / 356

181
Motor noise, EMI measures, mechanical resonance
4
P
ARAM
ETE
R
S
4.16 Motor noise, EMI measures, mechanical resonance
4.16.1 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.
(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% of the rated inverter current or higher while
Pr. 260
= "1 (initial setting)" and
Pr.
72 (inverter carrier frequency)

"3" (3kHz) (5kHz or higher under the IPM motor control), E.THT (inverter overload trip) is
likely to occur. To avoid that, the carrier frequency is automatically lowered to as low as 2kHz. (The 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 of Use Parameter that should 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. 260 181
Reduce mechanical resonance Speed smoothing control Pr. 653 182
You can change the motor sound.
Parameter
Number
Name Initial Value
Setting
Range
Description
72

PWM frequency
selection
1 0 to 15
You can change the PWM carrier frequency.
The setting is in [kHz]. Note that 0
indicates 0.7kHz and 15 indicates
14.5kHz.
0 to 4
: 2.5kHz
5 to 7 : 5kHz
8, 9 : 7.5kHz
10 to 12 : 10kHz
13 to 15 : 12.5kHz
240

Soft-PWM operation
selection
1

0 Soft-PWM is invalid
1
When the PWM carrier frequency ( Pr. 72 ) is 5kHz or less,
the Soft-PWM function is valid.
260
PWM frequency
automatic switchover
1


0 PWM carrier frequency is constant independently of load.
1
Decreases PWM carrier frequency automatically
when load increases.
The above parameters can be set when Pr.160 Extended function display selection = "0". (Refer to page 197)

These parameters allow their settings to be changed during operation in any operation mode even if "0" (initial value) is set in Pr.77 Parameter write
selection.

Performing IPM parameter initialization changes the settings. (Refer to page 85)

Performing IPM parameter initialization sets back the settings to the initial settings. (Refer to page 85)
NOTE
 Decreasing the PWM carrier frequency affects on EMI measures and on leakage current reduction, but increases
motor noise.
 When PWM carrier frequency is set to 1kHz or less ( Pr. 72

1), fast response current limit may function prior to stall
prevention operation due to increase in ripple currents, resulting in insufficient torque. In such case, set fast-
response current limit operation invalid using
Pr. 156 Stall prevention operation selection .
Parameters referred to
Pr. 156 Stall prevention operation selection Refer to page 96
V/F V/F V/F
GP
MFVC
GP
MFVC
GP
MFVC
IPM IPM IPM