Single phase motor running of 3 phase issues

[rshipman]

Hi, I have a Rusch 3 phase bandsaw. It takes 3phases and earth without the neutral. The bandsaw came with a single phase coolant pump motor which burnt out fairly quickly. So I replaced it with a different pump. It blew two of these. The original pump began smoking, but the replacements simply stopped working after a while. The wires to the pump are coloured blue, brown, green/yellow. Voltage across blue and brown is 400v. Voltage from blue or brown to green/yellow is 230v. So it looks to me like the single phase motor is being run from two phases of the 3 phase and earth is earth. Am I correct? Is there anything that could be causing these motors to die? Although I shouldn't have to (I may be wrong) is there a suitable relay or some such that I could fit between the wiring and the motor which allows me to connect a single phase and a neutral to the motor and use the supply from the bandsaw as the control signal? I'm wondering whether these single phase motors don't like a non-zero reference voltage etc etc.

FYI: The replacement pumps were: Vertex Coolant Pump 240 volt 1/8hp 130mm Stem

Any help gratefully received.

 

[Rob.]

What supplies the band saw? Is it 3ph & N or just 3ph? 

If it's just 3 phase the original could well have been a single phase 400V rated motor? 

Not entirely common, used in Europe more than here. 

 

[Evans Electric]

If you are connecting a 230V   Single Phase pump across a 400V  supply  ...as you have proved ..the windings will melt .  

I'm amazed the various pumps worked at all , I'd have thought BANG!!!!!  as soon as you powered them up.

As far as I can see you need a 400V  X 3phase  pump .

Or

A 230V single phase pump plugged in separately to a socket .

Or

Install a neutral to the machine & connect it that way .

If the pump starter is wired from the machine it must be a  3 ph  X 400V one  so where are these 230V pumps coming from.?  

 

[rshipman]

Thanks for the speedy reply!

That may be it. It is an Italian machine. Supply is 3PH, not 3PH+N.

So a single phase motor running off two phases needs to be 400v rated? I guess that makes sense in hindsight.

 

[Tony S]

Can you take a photograph of the motor plate? It would clear up a few things.

 

[Rob.]

400v two phase motors act as a single phase motor just at a higher voltage. 

Capacitors within them deal with the phase shift. 

Not something common, granted. I have just been looking at a job in Denmark using 4 of them tensioning paper. 

Called single phase as there are only two wire connection. 

 

[apprentice87]

Hi There,

You need something like one of these.. Just get someone that knows what they are doing to wire it in. Wonder you have not killed yourself already...

http://allpumps.co.uk/pumps/coolant-pumps

john...