Flux-Vector Variable Speed Motor

[zdas04]

It has been 34 years since I took my only Sparks and Magic course. I just came across a pump for Oil & Gas wells with a Flux-Vector Variable Speed Motor which the pump write-up says can stroke 25 times per minute (dead stop to moving in the other direction 50 times per minute) without a problem.

The motor is driving a pinion gear that rides in a rack attached to a downhole pump. On the upstroke the motor is lifting a bunch of weight (thousands of feet of steel and a bunch of water. On the downstroke it is trying to control the rate that the rods are falling. Every direction change, the motor has to stop and then start under load. This sounds really difficult to me.

Can anyone explain this Flux-Vector motor (if that is a real term and not just a made-up marketing thing) and give me an idea if starting under load 50 times per minute times 5 years is even possible. It is a fairly new pump that seems to be working well, but I'm trying to get my head around possible life expectancy.

Thanks for your help.

David

 

[Compositepro]

I'm guessing there is some gas spring or other device to balance the dead weight.

 

[zdas04]

If there is, it isn't obvious from their web site or from visiting field installations. Hopefully I'll be able to answer these questions next week.

David

 

[zdas04]

I met with the manufacturer today and on the downstroke the generated power is dumped into bank of resistors and converted to heat (they call it a "dynamic brake drum"). Been around for a while and in this application for 10 years.

David

 

[davidbeach]

Essentially unnoticeable when connected to a utility source. Will be very notifiable when connected as a significant portion of the load of a gen set.

 

[Skogsgurra]

If the genset doesn't deliver to any other loads (like lamps, other machinery etcetera), I don't think it will be much worse than running the rod directly off an ICE of the same size as the engine used for the genset.
The speed variation will actually be less because the downward part of the cycle doesn't affect the genset. The VFD must, of course, be able to run off the resulting varying grid. If those people have done this for a couple of years, or more, they should know how to handle it.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[zdas04]

The project is evolving and the man-camp has turned into a pretty big load. Now it looks like the entire peak load is around 600 kVA, and the pumps are about 9 kVA each so if all 5 of them sync up (pretty unlikely since they will be at least a third of a mile from each other) then they represent about 7.5% of the capacity. Sounds like nothing much to worry about.

I visited one of the pumps in operation this week and it was on a feeder line with two homes and the homeowners weren't complaining (and these people WOULD complain, they bitch about everything else that the oil company does).

David

 

[jraef]

If they notice anything, it might only be in their audio systems.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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