It's been number of years since I've logged on here. I thought I would take a stab at finding a resource that someone may have. Yesterday we ran into a problem with a turbine compartment cooling fan on a GE 7EA gas turbine. This particular 15 HP, 480 VAC, 3 Phase motor pulls air through the turbine compartment via louvers on the sides of the compartment, and exhausts the air through exhaust louvers on top of the unit. We were getting indications that we had a broken bar, or a cracked end ring in the rotor of this brand new motor (less than a week old). Without going into all the details, it was found that the rotation of the fan was backwards (mechanics don't know the difference between clockwise and counter-clockwise), and because of recent mild temperatures the turbine compartment stayed cool enough to prevent an alarm for over-temperature. We were expecting the motor to unload (phase amps to lower) if running backwards because of lack of air movement. That was not the case. Phase current actually increased, and the fan "appeared" to be running slower than normal giving us the impression that we had a problem with the rotor. Appearances can be deceiving. We swapped two leads, got the fan running in the right direction, and the world became a wonderfully sublime place again. The turbine is nice, cool, and happy again. All that being said, I'm looking for information on the relationships between motor loading, and various types of fans and pumps. If anyone can lend a hand, I would greatly appreciate it.

The Watt Doctor
Altura Cogen
Channelview, TX