Thread: Powering a 3phase pump with single phase

why not use an evaporative cooler pump?

Good call, but it costs $$. And SWMBO restricts all spending I'm trying to use what I have available.

It's not a matter of getting any old capacitor.
You will need a continuous duty or "run"type capacitors. The capacitance of the capacitors needed depends on on the power drawn by the motor under load and is often determined by monitoring the temperature of the motor under continuos load, rather than calculation. . Using the wrong capacitor in continuous service is liable to cook the motor and even start a fire not to mention electrocution risks.

In short (ha ha) a safer way to run this motor is not with capacitors but a single to 3 phase inverter.
However, an inverter will cost you about the same price as a new single phase coolant pump and motor.

A cheaper solution would be an aquarium pump or better still a water feature pump.
The problem with these is they don't like swarf as the very fine metal dust sticks to the magnets inside these motors but if you use filters and strong magnets in the return path this can be controlled
I've had mine running on my lathe for 4 years now and it is still going strong.

Thanks bobl. I understand the risks involved and I am aware that capacitors ain't capacitors.... I'm running with the 3 phase pump coz it's what I have, and it's an interesting project. I guess using a 240v pump would be safer, and easier, and maybe I could find a pump from a washing machine or fish tank etc. at the tip that could essentially to the job, but then i would have never learned that you can run a 3phase motor on a single phase power source, and how to fit it out. On the other hand, safer is best. I think I'll end up doing both. I'll got out the 3 phase on a single phase just to say "I did it", but to keep it safe (at home) I guess fitting a 240v pump is the best way to go in the end.

Could you make a rotary phase converter? A 3 phase motor driven by a single phase motor to make 3 phase for powering the pump. Shouldn't need large ones and scrounging might turn some up cheap or your wife's price of free.

I suspect that a single run capacitor costs as much as an a water feature pump.... Sorry.

Cheers,
Joe

Originally Posted by QC Inspector

Could you make a rotary phase converter? A 3 phase motor driven by a single phase motor to make 3 phase for powering the pump.

That is not really what an RPC is ... although they sometimes have a smaller single phase motor they use just to "spin up" the larger 3 phase motor, but that's pretty rare.

With the caps on the 3 phase motor (which is really a static phase converter), you normally select them by trial an error, like Bob said, however normally based on balancing the phase voltages under the expected load, rather than temperature, although you do need to do a general check to ensure that the motor isn't overheating.

As also mentioned you need run type caps.

We used to run some 3 phase motors on single phase and they ran for years. This was in a 1000MW state owned power station.
They used only 2 of the windings and a Cap made up the third side of the delta triangle.
Windings common was , say, neutral and active went to one of the either winding/cap connections.
This gave forward or reverse.

Hi MOA,
I have attached some data sheets on Motors for your reference and they sow single to three phase connections, as others have said the cost and trouble could not be worth it.
An other suggestion would be to modify the pump by taking off the three phase motor and grafting a singe phase motor to the shaft.

Keith_W

Originally Posted by Sterob

We used to run some 3 phase motors on single phase and they ran for years. This was in a 1000MW state owned power station.
They used only 2 of the windings and a Cap made up the third side of the delta triangle.
Windings common was , say, neutral and active went to one of the either winding/cap connections.
This gave forward or reverse.

Yep, this is exactly how I wanted to do it. Video explaining the method here:

Originally Posted by Keith_W

Hi MOA,
I have attached some data sheets on Motors for your reference and they sow single to three phase connections, as others have said the cost and trouble could not be worth it.
An other suggestion would be to modify the pump by taking off the three phase motor and grafting a singe phase motor to the shaft.

Keith_W

Thanks for the info Keith, I will read and keep it for future reference.

Hi Moa,

I can very much appreciate wanting to use the items you have available. Sometimes though it's easier to buy the proper item in the first place instead of modifying what you have. BUT, it is always worth a look at trying.

I always try to use what I have at hand before spending cash. I don't think it's because I'm a tight wad, I think it's cause I like the challenge of making things as cheap and good as possible. Making something from "nothing" is so rewarding!

Good luck with finding the correct caps and getting it to run. It's only a coolant pump so it does not need to be super smooth and it was free so you have nothing to loose!

Simon

Originally Posted by MOA

Yep, this is exactly how I wanted to do it. Video explaining the method here:

Hi MOA,

Depending upon how good your local scrap/salvage yard is, many washing machines have capacitor start and run main motors on them. You could salvage some capacitors that way or even the whole motor. Also, at least here in the UK, suitable capacitors are not particularly expensive. I got a replacement 8uf 250 volt AC capacitor for £3.95 (about $7 AU).