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Inverter ac drives with two-phase and three-phase PWM techniques
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| Author(s) |
S. Halasz; S. Pravadalioglu |
| Abstract |
Inverter-fed ac drives with two- and three-phase PWMs are compared from the point of view of motor
harmonic losses, torque ripples and inverter losses. The skin effect in rotor bars is taken into account.
The novel three-phase PWM, which can be constructed similar to the space vector method, is
suggested. This method produce scarcely lower harmonic losses and considerable lower torque ripples
than the space vector method. Computations are valid for two different, 3.3kHZ and 2kHz transistor
switching frequencies assuming that the whole or only 2/3rd of rotor resistance is affected by skin
effect. A special care was devoted to the overmodulation region. For this a novel two-phase PWM
schemes are suggested. For the same transistor switching frequency the fundamental voltage - where
the two-phase and three-phase PWMs produce the same losses - virtually does not depend on the skin.
In the whole normal voltage region the motor torque ripples and speed oscillations for the same
switching frequency are lower for the three-phase PWMs. This is true especially for the suggested
three-phase PWM since in this case the first side modulation harmonics do not produce torque
harmonics. The frequency converter conduction and switching losses in the case of the usually used
two-phase PWM are about the same than those in the case of three-phase PWMs. |
| Download |
| Filename: | EPE2001 - PP01074 - Halasz.pdf |
| Filesize: | 247 KB |
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| Type |
Members Only |
| Date |
Last modified 2004-03-11 by System |
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