Mitsubishi Electric 700 Series, Instruction Manual

Page: 181 / 416

170
Motor noise, EMI measures, mechanical resonance
4.15.2 Speed smoothing control (Pr. 653, Pr. 654)
(1) Control block diagram
(2) Setting method
If vibration due to mechanical resonance occurs, set 100% in Pr. 653 , run the inverter at the frequency which
generates maximum vibration and check if the vibration will be reduced or not after several seconds.
If effect is not produced, gradually increase the
Pr. 653 setting and check the effect repeatedly until the most
effective value is set in Pr. 653 .
If vibration becomes large by increasing the Pr. 653 setting, gradually decrease the Pr. 653 setting from 100% to
check the effect in a similar manner.
When the vibrational frequency due to the mechanical resonance (fluctuation of torque, speed, and converter
output voltage) is known using a tester and such, set 1/2 to 1 time of the vibrational frequency to
Pr.654 . (Setting
vibrational frequency range can suppress the vibration better.)
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 86.)
⋅
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 ripple currents, 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 81
Vibration due to mechanical resonance influences the inverter control, causing the output current (torque) to be
unstable. In this case, the output current (torque) fluctuation can be reduced to ease vibration by changing the
output frequency.
Parameter
Number
Name
Initial
Value Setting
Range
Description
653
Speed smoothing control 0 0 to 200%
The torque fluctuation is reduced to reduce vibration due to
mechanical resonance.
654
Speed smoothing cutoff
frequency
20Hz 0 to 120Hz
Set the minimum value for the torque variation cycle
(frequency).
The above parameters can be set when Pr. 160 User group read selection = "0". (Refer to page 190)
....
Specifications differ according to the date assembled. Refer to page 400 to check the SERIAL number.
CAUTION
⋅
Depending on the machine, vibration may not be reduced enough or an effect may not be produced.
Acceleration/deceleration
processing
Speed
command
V/F control
Current for torque
Frequency output
Voltage output
+
-
Proportional gain
Pr.653
Output frequency
Cutoff frequency
Pr.654
Speed smoothing control
0 Vibrational frequency 159Hz (fixed)
Torque fluctuation
detection range
Cutoff frequency
Pr.654
Current for
torque