Motor Noise, Emi Measures, Mechanical Resonance; Pwm Carrier Frequency And Soft-Pwm Control (Pr. 72, Pr. 240, Pr. 260) - Mitsubishi Electric FR-D720-008 Instruction Manual

Motor noise, EMI measures, mechanical resonance

4.15 Motor noise, EMI measures, mechanical resonance

Purpose of Use
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
Number
72 * PWM frequency selection
Soft-PWM operation
240 *
selection
PWM frequency
260
automatic switchover
The above parameters can be set when Pr.160 Extended function display selection = "0". (Refer to page 160)
* The parameters in the table allow its setting to be changed during operation 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.
(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 Pr. 260 = "0" (initial value), the carrier frequency becomes constant (Pr. 72 setting) independently of the load,
making the motor sound uniform.
When continuous operation is performed at 85% or more of the inverter rated current with the carrier frequency of the
inverter set to 3kHz or more (Pr.72 ≥ "3") while Pr.260 = "1", the carrier frequency is automatically reduced to 2kHz to avoid
E.THT (inverter overload shutoff). (Motor noise increases, but it is not a failure.)
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
146
Carrier frequency and
Soft-PWM selection
Speed smoothing control
Name Initial Value
1
1
0
Refer to page 77
Parameter that should be Set
Pr. 72, Pr. 240, Pr. 260
Setting Range
0 to 15
0
1
0
1
Refer to Page
146
Pr. 653 147
Description
You can change the PWM
frequency. The setting is in [kHz].
Note that 0 indicates 0.7kHz and 15
indicates 14.5kHz.
Soft-PWM is invalid
When Pr. 72 = "0 to 5", Soft-PWM is valid.
PWM carrier frequency is constant
independently of load.
Decreases PWM carrier frequency
automatically when load increases.
carrier