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#169308 - 10/01/07 10:40 AM phase rotation
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
Hi to all,
I used to be a member here a few years back and have decided to sign back up now i have a computer again!
My current problem is that whilst i understand the concept of phase rotation,i am failing to see how the below link demonstrates identification of phase rotation with "scewing the current and voltage".
Any help is much appreciated.
ps is there any half decent free electrical simulation programs that anyone knows of,i have used p spice but i think that is more of an electronic program.

http://www.allaboutcircuits.com/vol_2/chpt_10/3.html

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#169334 - 10/02/07 03:50 AM Re: phase rotation [Re: james S]
SteveFehr Offline
Member

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
Phase rotation won't impact current and voltage, not directly at least- the same voltage and current is flowing through the wires regardless of the order they're hooked up in. The biggest problem is that motors will rotate backwards.

Or, in installations with multiple power sources (EG, generator or redundant services), phase reversal at transfer switches and the like can cause BIG problems.

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#169415 - 10/04/07 11:35 AM Re: phase rotation [Re: SteveFehr]
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
I dont understand if the current and voltage does not have a direct impact then why is there less voltage on one bulb when illuminated.I have found a similar example in a text book and it says "due to the phasor addition of the voltage in the circuit then one set of bulbs will be dim"(they used two lamps in that example).
I think im missing something really silly here!!!!

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#169418 - 10/04/07 02:50 PM Re: phase rotation [Re: james S]
SteveFehr Offline
Member

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
It only occurs in that one specific example because of the way the RC circuit is designed; the capacitor has a reactive response 90┬░ out of phase, which creates current on that phase close to being aligned with one of the bulb phases, and close to out-of-alignment with the other. When you reverse phase rotation, that alignment reverses, too, and the other bulb dims/brightens. It's nothing inherent to phase rotation, just an example of how improper phase rotation can mess with a circuit.

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