4.16 Motor noise, EMI measures, mechanical resonance
Purpose of Use
Reduction of the motor noise
Measures against EMI and leakage
Reduce mechanical resonance
4.16.1 PWM carrier frequency and Soft-PWM control (Pr. 72, Pr. 240, Pr. 260)
You can change the motor sound.
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
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)
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.
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.
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.
Decreasing the PWM carrier frequency affects on EMI measures and on leakage current reduction, but increases
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
Motor noise, EMI measures, mechanical resonance
Parameter that should be Set
Carrier frequency and
Speed smoothing control
0 to 15
Refer to page 96
Pr. 72, Pr. 240, Pr. 260
You can change the PWM carrier frequency.
The setting is in [kHz]. Note that 0
0 to 4
5 to 7
10 to 12 : 10kHz
13 to 15 : 12.5kHz
Soft-PWM is invalid
When the PWM carrier frequency (Pr. 72) is 5kHz or less,
the Soft-PWM function is valid.
PWM carrier frequency is constant independently of load.
Decreases PWM carrier frequency automatically
when load increases.
Refer to Page