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Discuss I have a motor supplied by 2 hot legs from 3 phase 480v. One line to motor is interrupted by a pressure switch. With one line to the motor hot at all in the Electrical Forum area at ElectriciansForums.net

Lucien Nunes

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The motor sees a single circuit from A, through itself, through the switch and back to B.
As far as the motor is concerned it functions exactly as if it was from one hot to neutral rather than one hot to another hot. As far as the user is concerned, the difference is that with only the B phase switched, the windings (and, as you noted the B lead from the switch to the motor) remain hot relative to ground all the time, so for safety it is better to switch both legs.

All normal motors will show continuity from all terminals to all other terminals, regardless of what type of starting etc. they use. Therefore if any one terminal is made hot, they will all read hot to a multimeter.
 
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Reply to I have a motor supplied by 2 hot legs from 3 phase 480v. One line to motor is interrupted by a pressure switch. With one line to the motor hot at all in the Electrical Forum area at ElectriciansForums.net

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