# Generators, how they work?



## guitarboyled (Jun 22, 2009)

First off, thanks to everyone for helping out with this basic stuff. I know there are tones of info out there but some of these concepts are not so easy to grasp and sometimes the little extra human explanation does a big difference.

My next question concerns the following web site “How a generator works”

http://www.generatorguide.net/howgeneratorworks.html

Question #1 – What is the purpose of the commutator? From what I can see it keeps the current positive from 0v to 120v for example instead of from 0v to 120v to 0v then to -120v 

What application requires such current?


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## Greg (Aug 1, 2007)

All generators produce an AC voltage, the commutator acts like a mechanical rectifier.

Anything needing a DC voltage. We had DC voltage cranes on one of my ships.


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## guitarboyled (Jun 22, 2009)

According to the upper graph and the voltmeter, the power seems to be following a sine wave and not a constant current. Is it DC none the less?


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## Larry Fine (Oct 24, 2007)

guitarboyled said:


> Question #1 – What is the purpose of the commutator?


If an armature has slip rings, then one end of its windings is always connected to the same conductor. As the winding rotates, the current through it reverses every 180 degrees as it passes the stator's + pole, then the - pole, then the + pole, etc., so the output is AC.

A commutator acts as a reversing switch, so every time the armature rotates 180 degrees, so does which conductor each end of its windings is connected to, so as the current flow reverses, the polarity of each output conductor is always the same, so the output is DC.


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## Larry Fine (Oct 24, 2007)

guitarboyled said:


> According to the upper graph and the voltmeter, the power seems to be following a sine wave and not a constant current. Is it DC none the less?


The output of the armature itself is always AC. The use of a commutator provides the DC generator output; slip rings provide the AC directly to the output.


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