Run a 3 phase lathe coolant pump on single phase.

[Pete.]

Here's a trick I learned from John Stevenson a while ago. 3 phase coolant pumps are quite happy to run on single phase using the same principle as rotary converters. All you have to do is wire a small capacitor like the ones you find in the old strip lights to the third phase and it'll work just fine. To demonstrate, I quickly lashed-up a small pump I have here with a 10uF 250v capacitor. My pump here is dual-voltage but I am pretty sure it would work just as well if it were 415v only. They don't use a lot of power and there's no starting load.



Anyway, here's the vid of it starting and running.

3 phase suds pump on single phase with capacitor

 

[Dieselman 63]

Legend. Thanks very much for this!

 

[Newlands]

It's called a Steinmetz connection. As a rough guide the capacitor size can be worked out with this:
The capacitor size could be calculated by this formula:
C= 50 x P x (220/V)2 x (50/F)
C= microFarads, P= power output in CV, V= Voltage, F= Frequency.
CV stands for chevalier vapour (but we call it horse power..)

I tried this formula for my little bandsaw and it suggested about 42uF. When I measured the voltage at each phase there was a fair bit of imbalance, and the motor got fairly warm. I ended up reducing the size of the capacitor, down to 32uF.
If the motor is a 440v star connected, you have to change it to delta so it runs on 240v. Not all motors can be reconfigured easily, and some (like the coolant pump motor on my Harrison lathe) are impossible to reconfigure because of the way it's constructed.
There is a bloke called Andy Reynolds on YouTube who has about 6 videos on this topic.

 

[Pete.]

You don't strictly HAVE to have a delta-configured motor to run from 240v. You just de-rate the motor by running it on star but it will run.

 

[normspanners]

or use a 415 - 230v or poss a 230- 110 tranny backward on 230 to get 440 ish that would be an isolating tranny
or a centre tapped 110 and put 230 across the normally 55v -0v then across the two outer terminals you will get 440v ish - that would be a boost / or auto and that would not be isolating.
I use a standard 230 110 tranny backward on my fitted genny traffic light trailer, 110 genny and use 230 tools off it.

 

[Pete.]

3 phase transformers not so cheap nor common though.

 

[Maker]

3 phase transformers not so cheap nor common though.

I think he meant a single phase transformer (Or technically split phase?) and the cheeky capacitor trick.

I've got a 3 phase coolant pump somewhere, I'll give this a try tomorrow.

 

[normspanners]

they are not 3 phase they are single you cant get 3phase to single phase really you have to use a 3phase tranny in open delta.

 

[normspanners]

I think he meant a single phase transformer (Or technically split phase?) and the cheeky capacitor trick.

I've got a 3 phase coolant pump somewhere, I'll give this a try tomorrow.

Sneakin in under the back door, eh you young whipet snapper

 

[Maker]

Okay it wasn't tomorrow like I said but I finally dug out my pump, wired it for 230v and connected a 12 microfarad capacitor (Because that's what I had):

It's a tiny bit rougher than it was on my inverter but I'm very happy with it.

 

[normspanners]

It is tomorrow, well, if yesterday is anything to go by,and it did go by so it must be, but if it was tomorrow that would make it thursday wouldnt it and as you are in earth dimension C ,it might even be the day after. I would check before going out just in case you are already out. was it 230 or 415 ?

 

[Maker]

Do you find it runs a bit hot Pete? I've just had mine going for 30-40 minutes and the body was a little more than 60 degrees. I'm not sure how hot they can get before damaging the windings.

 

[WorkshopChris]

Do you find it runs a bit hot Pete? I've just had mine going for 30-40 minutes and the body was a little more than 60 degrees. I'm not sure how hot they can get before damaging the windings.

Does it have a insulation class mark on the data plate? F is a common rating.
https://en.wikipedia.org/wiki/Insulation_system
Industrial motors will run hot in normal use. If downrated with inverters if is sometimes necessary to fit a forced air cooler.
As the standard fan is not running fast enough to cool the motor.
I used to work with temperature sensitive materials. We use to water cool the pump shaft to prevent the pump motors adding to much heat to the system.

 

[Dieselman 63]

Is your sump full? My Colchester pump has a bored sleeve allowing the water/oil mix to cool the shaft. I too found the motor heats up a little, but I haven't run it it full yet.

 

[Pete.]

Check the voltage on the spare leg. You might have to adjust the capacitor size.

 

[Maker]

Phase voltages are all over the show!



It's plugged into an extension lead but I don't think that explains why my mains supply is so low, I'll try it at a few different times of the day and see how it is. I'll see if I can borrow a clamp meter too and see how much current it's drawing.

 

[Ed.]

Why do you even need a capacitor?

 

[WorkshopChris]

Why do you even need a capacitor?

To provide a offset to the voltage to allow rotation, just the same as a start capacitor on a single phase motor.
Without the cap you would just have a expensive short lived heating element.

 

[Ed.]

I thought that it was in reference to taking 240V off one of the 3 phases only? Reason is, I have quite a few 240V GPO outputs connected to my 3 phase sockets in the shed and every thing that is connected to them runs fine, so wasn't thinking about the 3 phase motor bit being run of a single phase.

 

[normspanners]

I did ask previous is it 230 or 415 ?

I have quite a few 240V GPO outputs connected to my 3 phase sockets in the shed

you would need a neutral though one of the problems of doing that is you can overload the neutral in the run from the CU to socket l