| > This would be ok if you were using a single phase induction motor, which | is | > not sensitive to phase rotation. I Know the type of pump arrangement. | When | > the pump goes one way it pumps and when it goes the other it acts as a | > turbine. | | | Huh? (again) | | If you have a three phase inductor MOTOR running happily along and you use | some external agency to force the shaft to turn faster than "sync" speed, | the motor will become a generator. |
I am not disputing this. Did I say I was? In fact, further in my post I said just the same thing.
The comments about direction were added in because it APPEARS that Mr Phillips has the idea that the reversing direction is important from the motor generator point of view, Whereas, it is really related to the function of the pump / turbine operation.
The purpose of my post was to support Mr Phillips because he was actually describing a real operation of something he has seen. ( and that I have also worked on, 40 Mw in fact) I was simply trying to clear up the issue about why the thing had to go backwards to act as a generator. It was not an electrical issue, but an hydraulics issue only.
| Now some water turbines might well be reversed to have them PUMP water in | the reverse direction but that's a separate issue. |
Actually it WAS the issue in this case :o)
| OT: often, "they" start pumps (except for positive displacement pumps) | with the outlet valve CLOSED. Since the motor isn't don't any work, it is | easier to start that way.
And even easier to start if the water is removed completely. In the system I worked on, in which the pump was below water level, They pump in high preasure Air to force the water level down below the turbine so the starting was done in just air. Once the thing was started, the air was vented and the water flooded in, The outlet was oppened, and the serious work began.