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John Deere Tractors Discussion Board |
Re: John T or Gerald J Simple Question...
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Posted by jdemaris on December 28, 2009 at 10:44:53 from (67.142.130.35):
In Reply to: John T or Gerald J Simple Question... posted by B-maniac on December 28, 2009 at 10:16:30:
A generator gets itself "started" due to a weak magnetic field that must exist in the field coils of the generator. That field must be the correct polarity for the generator to work. To polarize, you just send power to those fields for a second to establish that field. It can be done without the engine running. All you are doing is, by hitting the fields with power, making them work as an electromagnet while that power is on, and when "off", they retain some of that magetism so the generator will work the next time, without any power added. Alternators differ because they work by always feeding power at first to make the "excite" magnets work. They do not rely on residual magnetism like a generator does.
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