153
Motor noise, EMI measures, mechanical resonance
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4.15
Motor noise, EMI measures, mechanical resonance
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 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
t
"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.
Purpose
Parameter that must be Set
Refer to
Page
Reduction of the motor noise
Measures against EMI and leakage currents
Carrier frequency and
Soft-PWM selection
Pr. 72, Pr. 240, Pr. 260
153
Reduce mechanical resonance
Speed smoothing control
Pr. 653, Pr. 654
154
You can change the motor sound.
Parameter
Number
Name
Initial
Value
Setting Range
Description
72 *
PWM frequency selection
2
01160 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.)
01800 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 01800 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
t
"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 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
.
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 (
Pr.72
d
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
.
i
Parameters referred to
i
Pr.156 Stall prevention operation selection
Refer to page 70
Summary of Contents for F700
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Page 340: ...331 MEMO ...
