3 phase motor rotation
3 phase motor rotation
(OP)
Given an 800hp G.E. Motor directly coupled to a fan why would the manufacturer stipulate the Motor as CW or CCW? I thought that three phase Motors could be reversed by simply switching stator conductors. There is no anti-rotation device.





RE: 3 phase motor rotation
*Why a man thinks he outrun a chasing dog when it has twice as many legs?*
RE: 3 phase motor rotation
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 3 phase motor rotation
Axial flow fans are also unidirectional.
*Why a man thinks he outrun a chasing dog when it has twice as many legs?*
RE: 3 phase motor rotation
Also, the motor must rotate in one or other direction given a standard A-B-C phase rotation. Perhaps it is as simple as that.
----------------------------------
Sometimes I only open my mouth to swap feet...
RE: 3 phase motor rotation
We were involved a few years ago in a nuclear power plant and if these fans happened to run in reverse it would have been a case of "last man out turn the lights off..."
RE: 3 phase motor rotation
Larger motors, e.g. the 800hp in the OP can have a unidirectional fan, thus the rating plate will give a direction of rotation. You can swap two phases to reverse the motor, but the cooling airflow will be reduced and the motor rating will be reduced.
These larger motors are usuallly built to order, rather than for stock. If the motor has a single radial fan, you may be able to unbolt it and reverse it, so it works in the other direction. Other designs may not enable you to do this.
Scottyuk, a simple journal bearing will rotate in either direction, but some more complex bearings (eg the offset halves bearings I saw on some turbo exciter bearings), would not. I think some bearings I saw on large vertical motors were unidirectional, because they had scoops to pick up oil to lubricate the bearing.
RE: 3 phase motor rotation
----------------------------------
Sometimes I only open my mouth to swap feet...
RE: 3 phase motor rotation