# Parallel Synchronous Generators

1. Nov 15, 2007

### scothoward

Hi,

I am having trouble understanding the three light bulb method for checking whether of not two generators have the same phase sequence. It states in my book, "If all three bulbs get bright and dark together, then the systems have the same phase sequnce."

My question is, if the two generators have the same phase sequence, and the voltages generated in each phase are the same, how will there even be a potential difference across the bulb to allow it to light up?

I am not sure if my question makes sense....Im sure it is just a basic misunderstanding.

Thanks for the help

2. Nov 15, 2007

### Staff: Mentor

What are the frequency and voltage? 60 Hz, or variable? Low voltage, e.g. 10-20 V or more standard like 110. Are the generators 3 phase, or single phase?

Two line in phase will have a pure sinusoidal voltage. If they are out of phase the max voltages will not coincide, so the current on a purely resistive ciruit will be lesser than if the two lines were in phase.

Think about what happens with V = cos wt + cos (wt+a), and in a three phases system, each phase is 120° or 2pi/3 out of phase with the other two.

3. Nov 16, 2007

### stewartcs

Does this diagram of a typical 3 phase AC synch. light connection help?

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