single to 3 phase, but with a transformer?

[flanajb]

Ok. You may remember that I managed to get a 3 phase vacuum pump running off 240v by wiring the motor in delta configuration and employing start and run capacitors. Well, I am getting ambition now and have my eye on a 3 phase low noise air compressor from clarke. It's 5.5hp and gives me the required free air delivery I need. A 240v machine will not provide the required FAD.

Now, I don't have the machine to hand, but I suspect wiring the motor in delta is not an option and as a result I will need to source a suitably sized 240v to 415v transformer and then employ start and run capacitors for the 3rd leg?

I just want to check with anyone whether this is viable or whether I still will have a setup that will not work very well?

Thanks

 

[dzj]

Maybe in theory, but you'll be taxing your primary circuit with ~30A of current.
Inrush current would be quite a bit more.

 

[Dee J]

Given the cost of the transformer... Wouldn't it be better to swap to a 240v single phase motor?

 

[flanajb]

Given the cost of the transformer... Wouldn't it be better to swap to a 240v single phase motor?

The motor needs to be 5.5hp, otherwise, it will not provide the compressor with enought power to generate the required free air delivery.

 

[beech1948]

Before making any decisions you need a bit more info.

1) many (most) 3 phase motors can be wired to accept both 220v and 415v 3 phase. So ask that question. Another way to ask is whether the motor is wired as Star or Delta config. You can rewire to needed config yourself.

2) If it will run with 220v 3 phase then smile and buy a VFD - 5.5 hp will be a few hundred pounds though. This would be the simplest way to go though possibly not the cheapest. As you start to research VFDs also ask any suppliers if they have any 2nd hand units. If not then you would need to start searching industrial salvage companies.

3) It sounds like your thinking of a self build for a transformer. Again ask the 220/415 v question. If 220v then maybe proceed but this would need some real plans and some skills and will not be tested. I would try to find an industrial electrician to help you.

 

[flanajb]

Before making any decisions you need a bit more info.

1) many (most) 3 phase motors can be wired to accept both 220v and 415v 3 phase. So ask that question. Another way to ask is whether the motor is wired as Star or Delta config. You can rewire to needed config yourself.

2) If it will run with 220v 3 phase then smile and buy a VFD - 5.5 hp will be a few hundred pounds though. This would be the simplest way to go though possibly not the cheapest. As you start to research VFDs also ask any suppliers if they have any 2nd hand units. If not then you would need to start searching industrial salvage companies.

3) It sounds like your thinking of a self build for a transformer. Again ask the 220/415 v question. If 220v then maybe proceed but this would need some real plans and some skills and will not be tested. I would try to find an industrial electrician to help you.

I was about to ask the difference between 415v star and 220v delta, but I now get that 415v star gives you 230v across the windings and 220v delta gives you 220v across each winding. I think that is correct?

So in essence, you still get the same amount of power from the motor?

The compressor in question is this one. https://www.machinemart.co.uk/shop/...-270ltr-low-noise-recipr?da=1&TC=RV-000115270

I have just looked at the product manual and the motor is listed as 400/50/3. That would indicate a step up transformer is required.

 

[flh801978]

You are not going to get a large 3 phase motor running easily with a home built single to 3 phase converter
A transformer is huge/expensive to carry the load required for 5.5kw
Inverters are expensive for that size
Star winding needs 415v across the windings /connection points
delta needs 240v
Best to buy a single phase compressor ...or 2 if you need more air

Or buy something from a supplier that works on single phase
You will need a large single phase supply > 40 amps

Ian

 

[beech1948]

flanajab,

Maybe consider https://www.machinemart.co.uk/shop/product/details/se29d270-ol-air-compressor also from Machine Mart ---spec'd to 28cfm and single phase.

 

[flanajb]

I could build my own step up transformer?

As to single phase units. Even with a 4hp motor the free air delivery is not great. Agreed, I could buy 2 units and have them feed a single receiver, but that just seems rather nuts.