Mitsubishi Electric FR-A700 Technical Manual page 396

2.20.8 PWM carrier frequency and Soft-PWM control [Pr. 72, 240, 260
You can change the motor sound. Increasing PWM carrier frequency will reduce the motor acoustic noises, but increases EMI
and leakage current from the inverter.
[Pr. ] Name
PWM frequency
72
*
selection
Soft-PWM
240 operation
*
selection
PWM frequency
260 automatic
switchover
* The parameters in the table allow its setting to be changed during operation even if [Pr. 77 Parameter write selection = 0] (initial value).
(1) PWM carrier frequency changing [Pr. 72]
You can change the PWM carrier frequency of the
inverter.
Changing PWM carrier frequency is useful for the
following purposes:
•To avoid mechanical or motor resonance
•To prevent EMI
•To reduce leakage current by PWM switching
When using an option sine wave filter (MT-BSL/BSC)
for the 75K or more, set [Pr. 72 = 25 (2.5kHz)]. When
[Pr. 72 = 25], V/F control is forcibly selected. At this
time, perform continuous operation at less than 90%
of the rated inverter output current.
When the carrier frequency is set to 3kHz or more
([Pr. 72 3]) to the 75K or more
perform continuous operation at less than 85% of the
rated inverter output current.
Carrier frequencies under Real sensorless vector
control and vector control by
below.
[Pr. 72] Setting
55K or 75K or
less more
0 to 5 0 to 5
6 to 9 6
10 to 13 —
14, 15 —
When PWM carrier frequency is set to 1kHz or less
([Pr. 72 1]), fast-response current limit may function
before stall prevention operation due to increased
ripple current, and torque may be insufficient. In such
case, set fast-response current limit operation invalid
using [Pr. 156 Stall prevention operation selection] .
Initial
Setting Range
Value
55K or
0 to 15
less
2
75K or 0 to 6,
more 25
0
1
1
0
1
F700
0
D700
1
inverter,
A700
are as shown
A700
Carrier Frequency (kHz)
2
6
10
14
(* [Pr. 260] is not available for
Description
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.)
Soft-PWM is invalid
When [Pr. 72 = 0 to 5] (0 to 4 for the 75K or more),
Soft-PWM is valid.
PWM carrier frequency is constant independently
of load.
Operate continuously at less than 85% of the
inverter rated current when carrier frequency is set
3kHz or more ( [Pr. 72 3] ) in
Decreases PWM carrier frequency automatically
when load increases.
(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.
0 2k 4k
Frequency [Hz]
(a) With Soft-PWM
0 2k 4k
Frequency [Hz]
(b) Without Soft-PWM
(When the motor SF-JR 4P 3.7kW carrier frequency
430
* ] common
(common)
Available Inverters
A700
—
.
F700
6k 8k 10k 12k 0
Since the frequency
dispersed, the sound becomes inoffensive
with less metallic noises.
6k 8k 10k 12k 0
Since the frequency
concentrated, metallic noises are generated.
Motor noises data example
2kHz is used)
PARAMETER
.)
A700 E700
F700 E700 D700
—
Noise level
12k
10k
8k
6k
4k
2k
0
4
Time [ s]
2
components are
Noise level
12k
10k
8k
6k
4k
2k
0
4
[ s ]
Time
2
components are