Re: MD-80 Electrical

Date:         18 Apr 98 00:49:21 
From:         "James M. Eadie" <>
Organization: The Boeing Company
References:   1
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Stein1111 wrote:

> Can someone help explane " 3 phase" when it comes to a 40KVA  115 volt and
> 3 phase output generator.  What does 3 phases do for you?

AC Generators are usually wound with three armature circuits which are spaced
120 degrees apart on the armature.  With a balanced load Y connection, the
three line and coil currents are equal, but the line voltages are sqrt(3)
times the coil voltages.  Thus, while three phase power requires three wires
instead of two, you can transmit 73.2% more power over these three wires than
in the two wires needed for the single phase power (for a given wire gage).
In an aerospace application, this allows use of larger gage wires (significant
weight reduction) to deliver the required load capability.