Friday, May 14, 2010

Single phase supply used to control a three phase motor via a variable speed drive?

i've got a huge assignment,but i just can't seem to find any info on this. my lecturer gave me the question exactly like this:


';In VSds, explain how a single phase supply can be used to control a three phase motor.';


Im desperate!!Single phase supply used to control a three phase motor via a variable speed drive?
you can control a 3 phase motor via a single phase supply by using a ';phase converter'; but i think your instructor meant ';VFD's';





look here:





http://en.wikipedia.org/wiki/Three-phase鈥?/a>





The answer you are looking for is:





Variable-frequency drives (also known as solid-state inverters) are used to provide precise speed and torque control of three phase motors. Some models can be powered by a single phase supply. VFDs work by converting the supply voltage to DC and then converting the DC to a suitable three phase source for the motor.Single phase supply used to control a three phase motor via a variable speed drive?
Since a VSD works by converting the input voltage to dc before converting that dc to variable frequency/variable voltage, the input can be single phase or 3 phase and the same for the output.





This will not increase the voltage so the motor must match the input voltage or use a transformer.
Yes the load can be heavy for the single phase. A Japanese co builds a power supply that converts the single phase to DC. Then the DC is pulsed in 3 phases and u can increase the speed or slow it down.
small heat pumps/airconditioning units use this technology. the compressor motor windings are all equal resistance like a 3 phase motor but run on single phase. they use inverter boards that do the switching. try looking at a daikan or mitsubishi aircon website.
Hi


There is no problem is driving a 3 phase motor from a single phase supply as outlines above by other contributers. There is a total power problem however. The largest motor will be limited by the supplier drive type. Not all manufacturers have an identical range but most will cover up to 2.5 kw or so. Motors are normall made so that they can run on 220 or 400 VAC 3 phase...a simple case of connecting the motor winding up correctly. Good firms to contact are Control Techniques, SSD Parker, Invertek, Seimens, Hitachi, ABB and so on..


Good luck

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