Mitsubishi Electric F700 User Manual

142
Motor noise, noise reduction
4.15 Motor noise, noise reduction
4.15.1 PWM carrier frequency and Soft-PWM control (Pr. 72, Pr. 240, Pr. 260)
(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 reducing noise or leakage current generated from the inverter.
(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 266 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.
You can change the motor sound.
Parameter
Number
Name
Initial
Value
Setting Range Description
72 * PWM frequency selection 2
55K or
less
0 to 15
PWM carrier frequency can be changed.
The setting displayed is in [kHz]. Note
that 0 indicates 0.7kHz, 15 indicates
14.5kHz and 25 indicates 2.5kHz.
(25 is exclusively for a sine wave filter.)
75K or
more
0 to 6, 25
240 * Soft-PWM operation selection 1
0 Soft-PWM is invalid
1
When Pr. 72 = "0 to 5" (
"0 to 4" for 75K or
more), soft-PWM is valid.
260
PWM frequency automatic
switchover
1
0
PWM carrier frequency is constant
independently of load.
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.
1
Decreases PWM carrier frequency
automatically when load increases.
The above parameters can be set when Pr. 160 User group read selection = "0". (Refer to page 156.)
* 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.
⋅ When using an option sine wave filter (MT-BSL/BSC) for the 75K or more, set "25"(2.5kHz) in Pr. 72.
CAUTION
⋅ Decreasing the PWM carrier frequency reduces inverter-generated noise and leakage current, 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 harmonic currents depending on the motor, 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 Refer to page 73

Mitsubishi Electric F700 Specifications

General

Brand	Mitsubishi Electric
Model	F700
Category	Inverter
Language	English