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Motor noise, EMI measures, mechanical resonance
4
PARAMETERS
4.16.2 Carrier frequency and Soft-PWM selection under IPM motor control
(Pr.72, Pr.240, Pr.260)
<IPM>
(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 unoffending complex
tone.
(3) PWM carrier frequency automatic reduction function (Pr.260)
⋅ If continuous operation is performed at 85% of the rated inverter current (the value in the parenthesis on page 346)
while Pr.260 ="1 (initial setting)" and Pr.72 ≥ "6 (inverter carrier frequency is set to 6kHz or higher)," E.THT (Inverter
overload trip) is likely to occur. To avoid that, the carrier frequency is automatically lowered 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.
You can change the motor sound.
Parameter
Number
Name Initial value Setting range Description
72 *1
PWM frequency
selection
2
55K or
lower
0 to 15
You can change the PWM carrier
frequency of the inverter.
0 to 5 : 2kHz
6 to 9 : 6kHz
10 to 13 : 10kHz
14, 15 : 14kHz
Pr.72 cannot be set to "25" during IPM
motor control.
75K or
higher
0 to 6, 25
240
*1
Soft-PWM operation
selection
1
*2
0 Soft-PWM is invalid
1 When Pr.72 ="0 to 5", soft-PWM is valid.
260
PWM frequency
automatic switchover
1 *3
0
PWM carrier frequency is constant
regardless of the load.
Perform continuous operation at less
than 85% of the rated inverter current
when the carrier frequency setting is
6kHz or higher (Pr.72 ≥ 6).
1
PWM carrier frequency is automatically
decreased when the load increases.
The above parameters can be set when Pr.160 User group read selection ="0." (Refer to page 201)
*1 The above 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.
*2 Performing IPM parameter initialization changes the settings. (Refer to page 80)
*3 Performing IPM parameter initialization sets back the settings to the initial settings. (Refer to page 80)
REMARKS
Pr.72 cannot be set to "25" during IPM motor control.
CAUTION
⋅ Decreasing the PWM carrier frequency is effective on EMI measures and on leakage current reduction, but increases motor
noise.
IPM
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