Delta Electronics VFD-E manual Method a Frame a Frame B & C, Method B Frame a Frame B & C

Chapter 4 Parameters
Carrier	Acoustic	Electromagnetic	Heat	Current
Frequency	Noise	Noise or leakage	Dissipation	Wave
		current
1kHz	Significant	Minimal	Minimal	Minimal
8kHz
15kHz	Minimal	Significant	Significant	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 heat sink temperature and output current of the AC motor drive. It is used as a necessary precaution to prevent the AC motor drive from overheating and thus extends IGBT’s life. Example for 460V models: Assume the carrier frequency to be 15kHz, the ambient temperature is 50 degrees C with a single AC motor drive(mounting method A). If the output current exceeds 80% * rated current, the AC motor drive will decrease the carrier frequency automatically according to the following chart. If output current is 100% * rated current, the carrier frequency will decrease from 15kHz to 12kHz.

Mounting method

Method A
Frame A	Frame B & C
120mm	150mm
50mm	50mm
50mm	50mm
120mm	150mm

Method B
Frame A	Frame B & C

4-54 Revision June 2008, 04EE, SW--PW V1.11/CTL V2.11