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Phase Converter Load Testing Rig

Keith Foor

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#1
So I had a thought while in the shower today. I was trying to figure out a load bank for testing RPC's. Thought came to me on how to load a motor so it would actually be working. Came up with locating 3 phase pump motors with the pump attached and a 55 gallon drum full of water. Pull the water from the bottom and pump it into the top with a restriction plate in the output line. This of course would build back pressure and cause the motor to actually do work.

I was never a fan of turning on a lathe, taking a cut with the lead screw and then running over and taking measurements. A rig like this could be several motors of various sizes all doing the same thing and then having metering in a panel with voltage and current for all three legs.

Any thoughts?
 

chips&more

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#2
Yeah one thought comes to mind. You put water, electricity, people and doing outside the norm can be an electrifying experience.
 

Rick Berk

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#4
Keith, what you are describing is a Go-Power Dyno which I had for many years testing the HP of Go Kart engines, another load bank I built for 3 phase small generator testing was 3 55 gallon barrels with water in them and 20-5500 watt water heater elements in each barrel, this was a very controllable load bank with 20 relays and 20 single pole switches on a control board, I could very quickly boil water and eventually added a water make up system with 3 toilet valves.
 

JimDawson

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#5
A centrifugal pump puts the max load on the motor at zero head, restricting the output actually puts less load on the motor. But, by putting a large valve on the outlet, you would be able to adjust the load.

A positive displacement pump loads the motor the most at shutoff, and in many cases will stall the motor at shutoff.
 

Keith Foor

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#6
I was thinking centrifugal pump so I will delete the restriction on the output. I am figuring a 3, 5, and 10 HP pump and just putting a 4 inch manifold on it to feed the pumps and 3 individual returns.
The reason for all this is I do work on RPC's a good bit, building and occasionally repairing.
I would rather have stuff I can say was load tested for 1 hour at the rated output and be able to show it as opposed to just hooking a second motor up with no load and running it calling it a load.

I have started and run 30 HP motors with a 10 HP RPC and it does so without any issues. Of course that ain't a real load. So I am trying to figure out a reasonable load to apply and test with.
 

Wireaddict

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#7
Rather than a restriction plate I'd use one or more gate valves [one per pump] to adjust the loading to the motors' full load current. I'd also locate the barrels away from the RPCs & motors, preferably in another room.
 

Keith Foor

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#8
yes water and electric don't mix well. Figuring on getting a small trailer to put all this on or a cart of some kind. Would have to be fairly heavy duty as the water is going to be over 400 pounds. One of those harbor freight fold up trailers ain't gonna cut it.
 

talvare

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#9
A centrifugal pump puts the max load on the motor at zero head, restricting the output actually puts less load on the motor.
Jim is correct about restricting the pump outlet.

I had another idea on a little different track for doing this sort of thing. How about utilizing an automotive rear axle assembly including the brakes and master cylinder assembly, coupling your 3 phase motor to the differential input yoke and applying the hydraulic brakes to increase load on the motor. This could also be put on a small trailer as you've suggested.

Just some food for thought.

Ted
 

Keith Foor

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#10
The thing I see with the axle is the length of run time and heat buildup in the brake system. It would be hard to deal with the heat from the friction on the brake pads. But that could be adapted to measure the torque on the brake mount and that combined with the RPM of the axle could be directly computed into horsepower.
 
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