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Chapter 4 Parameters|
4-40 Revision August 2008, 2ELE, V1.02
2kHz
8kHz
12kHz
Carrier
Frequency
Acoustic
Noise
Electromagnetic
Noise or leakage
current
Heat
Dissipation
Current
Wave
Significant
Minimal
Significant
Minimal
Minimal
Significant
Minimal
Significant
From the table, we see that the PWM carrier frequency has a significant influence on the
electromagnetic noise, AC motor drive heat dissipation, and motor acoustic noise.
The PWM carrier frequency will be decreased automatically by the ambient temperature and
output current of the AC motor drives. It is used to prevent AC motor drive overheat and
extend IGBT’s life. Therefore, it is necessary to have this kind of protection method. Take an
example of 460V models, assume that the carrier frequency is 12kHz, ambient temperature is
50 degrees C with single AC motor drive. If the output current exceeds 80% * rated current,
the AC motor drive will decrease the carrier frequency automatically by the following chart. If
output current is around 100% * rated current, the carrier frequency will decrease from 12k Hz
to 8k Hz.
Mounting method
Method A
Frame B
Frame A
150mm
150mm
5
0
m
m
5
0
m
m
Frame B
Frame A
Method B