Motor Noise, Noise Reduction - Mitsubishi Electric FR-F740 EC Instruction Manual

Parameter
6.14

Motor noise, noise reduction

Purpose
Reduction of the motor noise
Measures against EMI and leakage
currents
Reduce mechanical resonance
6.14.1 PWM carrier frequency and Soft-PWM control (Pr. 72, Pr. 240, Pr. 260)
You can change the motor sound.
Pr.
Name
No.
PWM frequency
72
selection
Soft-PWM operation
240
selection
PWM frequency
260
automatic switchover
The above parameters can be set when Pr. 160 = 0.
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".
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 reducing noise or leakage current generated from the in-
verter.
When using an option sine wave filter (MT-BSL/BSC) for the 01800 or more, set "25" in Pr. 72
(2.5kHz).
Soft-PWM control (Pr. 240)
Soft-PWM control is a control system 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% or higher of the rated inverter current (the value in
parentheses in Appendix A) with Pr. 260 = "1 (initial setting)" and Pr. 72 = "3" (inverter carrier fre-
quency is set to 3kHz or higher), E.THT (Inverter overload trip) is likely to occur. To avoid that,
the carrier frequency is automatically lowered to 2kHz.
(Motor noise increases, but it is not a failure)
When Pr. 260 is set to "0", the carrier frequency becomes constant (Pr. 72 setting) independent
of the load, making the motor sound uniform. Note that continuous operation should be per-
formed at less than 85% of the inverter rating.
FR-F700 EC
Initial
Setting Range Description
Value
PWM carrier frequency can be
01160 0–15
changed. The setting displayed is in
or (integral
[kHz]. The settings indicate the fol-
less value)
lowing frequencies:
2 0 ........................0.7kHz
01800
Settings between 1–14 correspond
or 0–6/25
directly to the frequency values.
more
15 ....................14.5kHz
25 ..................... 2.5kHz
0 Soft-PWM is invalid
1
When Pr. 72 = 0 to 5 (0 to 4 for
1
01800 or more), Soft-PWM is valid.
PWM carrier frequency is constant
independent of load. When the car-
rier frequency is set to 3kHz or
0
more (Pr. 72 ≥ 3), perform continu-
1
ous operation at less than 85% of
the rated inverter current.
Decreases PWM carrier frequency
1
automatically when load increases.
Parameters that must be set
Carrier frequency and Soft-PWM selection
Speed smoothing control
Motor noise, noise reduction
Refer to
Section
Pr. 72, Pr. 240, 6.14.1
Pr. 260
Pr. 653, Pr. 654 6.14.2
Parameters referred to
156 Stall prevention
operation selection
Refer to
Section
6.2.4
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