is this 3 phase?

[gsxr711]

Got given this a while ago and was told its was single phase but on closer inspection I think it is 3- phase .
If So does anyone know if I can change it to single phase? Also I fear the main on off switch is knackered
Here's some pics... Any help appreciated

 

[daleyd]

It is a 3 phase motor but you can run it from a single phase - 3 phase inverter as it has a 230v connection.

But you can't run it from straight single phase.

 

[rtbcomp]

Looks like someone's tried to wire it for single phase. The contactor coil looks like it's rated 380-440 volts, so it probably wouldn't work on 230v.

 

[daleyd]

Looks like someone's tried to wire it for single phase. The contactor coil looks like it's rated 380-440 volts, so it probably wouldn't work on 230v.

Yes, good spot I hadn't noticed the coil. I only looked at the motor plate!

 

[Pete.]

It is a 3 phase motor but you can run it from a single phase - 3 phase inverter as it has a 230v connection.

But you can't run it from straight single phase.

You probably can actually, though it might not be much good especially for a compressor. My tool and cutter grinder uses a 3 phase motor wired direct to single phase. It has poor starting torque but manages ok once up to speed. The spare leg of the three phase motor is connected to live via a capacitor.

 

[gsxr711]

Looks like someone's tried to wire it for single phase. The contactor coil looks like it's rated 380-440 volts, so it probably wouldn't work on 230v.

Yes that was me and my dad who is a sparky but hasn't had anything to do with motors since his teens! That is what we saw after opening the cover when the Sparks stopped!
What do you guys think I should do? Get a inverter? But they seem quite expensive unless I could use it to run other 3-phase tools?
Or try and run it single phase with a capacitor as mentioned above?

 

[waddycall]

You probably can actually, though it might not be much good especially for a compressor. My tool and cutter grinder uses a 3 phase motor wired direct to single phase. It has poor starting torque but manages ok once up to speed. The spare leg of the three phase motor is connected to live via a capacitor.

My bench grinder and pillar drill are both connected this way. Not sure it would work for a compressor due to the lack of starting torque. My pillar drill won't get up to speed on the top two of the 5 speeds (startrite Mercury). Grinder works a treat though. It's much better for motors that don't start under load.

 

[daleyd]

You probably can actually, though it might not be much good especially for a compressor. My tool and cutter grinder uses a 3 phase motor wired direct to single phase. It has poor starting torque but manages ok once up to speed. The spare leg of the three phase motor is connected to live via a capacitor.

I've never heard of that being done before, you live and learn!

 

[Wendelspanswick]

I've never heard of that being done before, you live and learn!

It's OK for a motor not under much load like a grinder or fan but would not work very well on a lathe or saw as the rated motor power is reduced and if the load slows the motor it will stall. The motors also tend to run hot as the load is not balanced.

 

[daleyd]

It's OK for a motor not under much load like a grinder or fan but would not work very well on a lathe or saw as the rated motor power is reduced and if the load slows the motor it will stall. The motors also tend to run hot as the load is not balanced.

I've worked with 3 phase motors for 20 years or more, but most of the stuff I have dealt with has been in factories etc so I've never had the need to use anything other than true 3 phase.

Amazing what blokes in their sheds can come up with as solutions though!!

 

[HughF]

buy an inverter, 2.2kw chinese ones are 89 quid or so.

 

[Fintray]

I've never heard of that being done before, you live and learn!

From Doubleboost's YouTube channel

 

[daleyd]

From Doubleboost's YouTube channel

To be fair, most of the ones I worked on were this size and above so realistically single phase was never going to work

 

[Fintray]

Yeah that would be pushing it on a 13A plug......

 

[waddycall]

It can work ok for lathes but it's best if they have a clutch so you can start them up with no load.
All explained in detail here-
http://www.amazon.co.uk/Electric-Motors-Home-Workshop-Practice/dp/1854861336

This book is definitely worth the asking price.

 

[gsxr711]

Looks like an inverter is the best bet has anyone got a link to the one I should get?
Here's a pic of the compressor, and a sticker on the side of the switch which I don't think matches what's inside it? This is the reason I thought it was single phase?

 

[HughF]

http://www.ebay.co.uk/itm/CNC-3KW-2...460?pt=LH_DefaultDomain_3&hash=item3aae86f5a4

One of those will do. Buy a new pressure switch and use the pressure switch to control the VFD via the interface terminals.

As the motor on your compressor is actually 2hp (1.5kw) then a cheaper, smaller VFD will be fine. There are often 2nd hand bargains to be had on ebay. I paid £35 for a 2kw one recently.

 

[gsxr711]

Excellent thanks il keep my eyes peeled for one!

 

[HughF]

Just watch that the one you bid on is definitely single phase input - there are 3 phase input vfd's floating about on ebay. Always look at pictures of the data plate, or ask for one.