Using System Protection Functions; Adjusting Carrier Frequency - Hitachi WJ Series User Manual

Chapter 9

9.10 Using System Protection Functions

9.10.1

Adjusting Carrier Frequency

 How to reduce the electromagnetic noise coming from the motor?
Q
 How to reduce the electromagnetic noise emitted by the inverter?
 How to reduce the heat generated by the inverter?
 How to prevent current leakage?
 The carrier frequency is the frequency of the PWM waveform output from the inverter.
A
 By setting a larger "Carrier frequency [b083]," the metallic noise from the motor can be reduced.
However, electromagnetic noise emitted by the inverter and current leakage may increase.
Changing the carrier frequency may also be effective in avoiding resonance in mechanical
systems and motors.
 The setting of "Load type selection [b049]" automatically limits the setting range of the carrier
!
frequency.
 The carrier frequency may be automatically reduced by setting "Automatic carrier reduction
selection [b089]" or by the DC braking function.
 The higher the carrier frequency, the more heat the inverter generates. Therefore, derating may
be required for the rated output current. The relationship between the carrier frequency and
output current derating differs for each model. For details, refer to "17.3 Current Derating".
 When "Control mode selection [A044]
frequency is automatically lowered to 2 kHz at low speed to maintain output torque even if
"Carrier frequency [b083]" is set to a value exceeding 2 kHz. In addition, since the carrier
frequency increases with acceleration, electromagnetic noise, etc. from the motor may vary
depending on the output frequency.
 The carrier frequency should be set to at least 10 times the "Maximum frequency [A004]".
(Example) When [A004] is 590 Hz, [b089] should be 5.9 kHz or higher
Code
Carrier
[b083]
frequency
■ Carrier frequency and its extent of the effect
Carrier frequency
Motor electromagnetic
sound
Electrical noise and
current leakage
Inverter heat generation
Example of inverter
output voltage
waveform
(PWM output)
*1. "2nd-motor control [SET]" target parameter. The second control parameter is also subject to setting.
Item
Sets the carrier frequency of the PWM
waveform output from the inverter to the
motor.
Carrier frequency: Low
*1
" is set to "Sensorless vector control (03)", the carrier
Description
Low
Loud
Low
Low
9-10-1
Inverter Functions
Data
2.0 to 15.0 (kHz) (ND mode)
2.0 to 10.0 (kHz) (LD mode)
High
Quiet
High
High
Carrier frequency: High