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Mitsubishi Electric FR-F740-00023 Instruction Manual: Motor Noise, Emi Measures, Mechanical Resonance; Pwm Carrier Frequency And Soft-pwm Control (pr. 72, Pr. 240, Pr)

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4.15 Motor noise, EMI measures, mechanical resonance

Purpose
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
Name
Number
72 *
PWM frequency selection
Soft-PWM operation
240 *
selection
PWM frequency automatic
260
switchover
The above parameters can be set when Pr. 160 User group read selection = "0". (Refer to page 173.)
* 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.
(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 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)
When continuous operation is performed at 85% or more of the inverter rated current (the parenthesized value of
the rated output current on page 304 or more) with the carrier frequency of the inverter set to 3kHz or more (Pr. 72
"3"), the carrier frequency is automatically reduced to 2kHz to protect the output transistor of the inverter. (Motor
noise increases, but it is not a 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.
CAUTION
Decreasing the PWM carrier frequency effect on EMI measures and on leakage current reduction, but increases motor noise.
When Pr. 570 = "0" (initial value), functions of Pr. 260 become invalid. PWM carrier frequency automatically decreases when load
increases. (Refer to page 75.)
When PWM carrier frequency is set to 1kHz or less (
operation due to increase in ripple currents, resulting in insufficient torque. In such case, set fast-response current limit
operation invalid using
Pr.156
Parameters referred to
Pr.156 Stall prevention operation selection
Carrier frequency and
Soft-PWM selection
Speed smoothing control
Initial
Setting Range
Value
01160 or
less
2
01800 or
more
1
1
Pr.72
Stall prevention operation selection.
Refer to page 70
Motor noise, EMI measures, mechanical resonance
Parameter that must be Set
Pr. 72, Pr. 240, Pr. 260
Pr. 653, Pr. 654
PWM carrier frequency can be changed. The
0 to 15
setting displayed is in [kHz]. Note that 0 indicates
0.7kHz, 15 indicates 14.5kHz and 25 indicates
2.5kHz.
0 to 6, 25
(25 is exclusively for a sine wave filter.)
0
Soft-PWM is invalid
When Pr. 72 = "0 to 5" (
1
more), soft-PWM is valid.
PWM carrier frequency is constant independently
of load.
0
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.
Decreases PWM carrier frequency automatically
1
when load increases.
1), fast-response current limit may function prior to stall prevention
Refer to
Page
153
154
Description
"
"
0 to 4
for 01800 or
153
4

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