3 phase power

[bannerd]

Hey all, just picked up a three phase air compressor. My question is, I have 100amp breaker box of single stage power to the shop. The motor requires a 30 amp breaker at 220v to push the 5hp motor. The required line is 10AWG or 14THW. If I hook up the motor to a 50AMP breaker would this melt my panel? I know with 3 phase that it's off loading the power down l1,l2,l3 on a breaker box. This is just to get the motor to rub properly. The motor is a Baulder motor and I don't want to melt it.

What do you all suggest? It does have a 3 phase magnetic starter on it. Which I would assume I'm going to need a single phase magnetic starter? At a lost on what I can do unless I spend large money to actually drop three phase there.

 

[bannerd]

I was looking at a rotary box as well, but I'm not sure if these are going to be replaced every year. Capacitors seems to go on them in doing some research.

 

[bsg]

Why would you try and run a 30 amp load on a 50 amp breaker?

You need three phase power to start that compressor, no way around it without buying a new motor and controls to change it to single phase.

I don't know where you got your info on the converter, some of them run for years without any problems.

Do you plan on buying any other three phase equipment, mill or lathe?

If you do, what I would do is put in a three phase panel fed from a rotary converter.
There are lots of options here and you will need to plan out what would be the best solution for you.

Three phase power in the shop is not that hard to do but you have to plan ahead.

You first have to ask yourself, is this the only piece of machinery that will require three phase?

Kevin

 

[MixManSC]

Yep.... there is really no viable way to run that motor on single phase power. You either need a phase converter or change out the motor on the compressor to a single phase motor. If you want a Baldor single phase 5HP motor you are looking at $350 to $450 - or you could go with another brand motor and probably get that cost down to $200(ish). Even lower if you can find a used motor. Just needs to be the same speed, mounting, shaft size, and duty cycle.

 

[Strouty]

An air compressor is the worst choice for a converter. Just change the motor. I will be interested to see if we are missing something from the OP or if he just doesn't understand.

 

[wyliesdiesels]

Hey all, just picked up a three phase air compressor. My question is, I have 100amp breaker box of single stage power to the shop. The motor requires a 30 amp breaker at 220v to push the 5hp motor. The required line is 10AWG or 14THW. If I hook up the motor to a 50AMP breaker would this melt my panel? I know with 3 phase that it's off loading the power down l1,l2,l3 on a breaker box. This is just to get the motor to rub properly. The motor is a Baulder motor and I don't want to melt it.

What do you all suggest? It does have a 3 phase magnetic starter on it. Which I would assume I'm going to need a single phase magnetic starter? At a lost on what I can do unless I spend large money to actually drop three phase there.

The only way to run a 3-phase motor on single phase power is to use a converter. Changing the breaker will do nothing. No u wont burn up your panel but instead burn up the motor because its single phasing which will cause it to overheat!

I would build an RPC!

For wire u need either #14 THHN or #12 NM-B. #10 is overkill. 30a breaker should be fine!

 

[Bib Overalls]

A simple static phase converter will cut your hp by 1/3 and that will certainly affect your compressor's efficiency. What you need is a rotary phase converter with an idler motor of at least 7.5 hp and 10 hp would be better. I have had good luck with rotary phase control panels made by Phase-Craft and sold on eBay. Talk to Jim at Phase Craft. He is a good guy and honest with his recommendations.

 

[bannerd]

Looks like I need to run a rotary phase converter. The motor on there now is about $2,000 and is a baulder motor. The Maximum amps it requires is 30AMP so I will need to pick one of those up. I can't run a single phase motor on this unit, the magnetic starter is all three phase. To replace that I would be spending a lot of money. The air compressor was a really good but, picked it up for $200.

Also, this will be the only piece of machinery that will require three phase. I don't think down the road we will ever get into machinery.

http://www.ebay.com/itm/5-HP-ROTARY...607?pt=LH_DefaultDomain_0&hash=item45fa633b0f

Bib Overalls: Those looks like really good buys, thanks!

 

[sberry]

No matter how cheap it is the thing is scrap unless you have the power to run it, this is not for you. Buy a new motor or sell it to someone that can use it.

 

[ddawg16]

A rotary phase converter or single phase to 3-phase VFD will cost more than a new 240Vac single phase motor.

Then you sell the 3-phase motor on Ebay and get half your money back.

 

[sberry]

This is where internet advice gets skewed. All that equipment is for a different user unless he wants to admitedly fart and fiddle. The motor on there might be 2 grand new in some cases but not in the used market. There is a glut and shortage of single phase.
Its why that gem was 200$, if the pump is a treasure and it has a good tank its worth a new quality motor. I have a 3ph controller on one of my old units, someone give it to me.

I live on rural power, nearest 3 is 2 miles, wish it would come by with new poles etc. I do have 400A service but part of it is I can and didn't cost me anything when I did service upgrade. There are some guys that can, I can, my neighbor can do without another layer of equipment above 50A, one has a converter and 1 planer, the whole setup is a space hog, just a bunch of extra stuff. He can and had free parts.

I wanted to stay in a world I didn't have to modify service every time I shifted something around or wanted to use elsewhere.

 

[sberry]

I use 2 comps, a 3 and a 5. Its all hooked together so I got about 200 gallon on, reduces cycles. But the high dollar 3 hp is nicer to the service. I just ran the other one a couple cycles while I was putting new brgs in the 3,,, could tell when the 5 came on.

 

[bannerd]

Thanks for the ideas, I went out to the shop and looked over the compressor again. It looks like the huge magnetic starter on there can be converted to single phase using the L1, and L2. I'm going to try and source a single phase 220v motor, be the easiest route.

The closest three phase power to use is ten miles, which would cost way to much to actually get installed. If we decided to get more three phase equipment we will have to look into converters.

 

[sberry]

That is the best thing to do, its simple, going to work, cant miss.

 

[930dreamer]

Look at building a simple rpc and keep all the existing wiring.

 

[teamextreme]

The 3 phase starter can be used on a single phase system, it's done all the time in industrial applications. You just have to run one of the legs thru 2 of the starter contacts (load side of B phase to line side of C phase, connect motor to A and C phase)

 

[larry_g]

Looks like I need to run a rotary phase converter. The motor on there now is about $2,000 and is a baulder motor. The Maximum amps it requires is 30AMP so I will need to pick one of those up. I can't run a single phase motor on this unit, the magnetic starter is all three phase. To replace that I would be spending a lot of money. The air compressor was a really good but, picked it up for $200.

Also, this will be the only piece of machinery that will require three phase. I don't think down the road we will ever get into machinery.

http://www.ebay.com/itm/5-HP-ROTARY...607?pt=LH_DefaultDomain_0&hash=item45fa633b0f

Bib Overalls: Those looks like really good buys, thanks!

I would really like to see pictures of this set-up. Include the nameplate on the motor please. With this information we can give you a lot better detailed advise. Realize that the unit linked to on e-bay will also require you to purchase an additional 3 phase motor for the 'rotary' part of the converter. What is being sold is only part of a rotary converter setup.

lg
no neat sig line

lg
no neat sig line

 

[wyliesdiesels]

The 3 phase starter can be used on a single phase system, it's done all the time in industrial applications. You just have to run one of the legs thru 2 of the starter contacts (load side of B phase to line side of C phase, connect motor to A and C phase)

Why do u have to do that? I have seen 3-phase starters used with only 2 contacts connected...

 

[teamextreme]

Why do u have to do that? I have seen 3-phase starters used with only 2 contacts connected...

That's the manufacturer's recommended connection (Eaton, who we use most, at least) Actually, it might only be applicable to electronic overloads, which I know monitor current in all phases and will detect a current imbalance and shut down if one leg is not drawing current. Traditional starters may not do this and you can get away with it, although I was pretty certain they all would, because an O/L on one phase without opening the other legs would single phase the motor.

 

[wyliesdiesels]

That's the manufacturer's recommended connection (Eaton, who we use most, at least) Actually, it might only be applicable to electronic overloads, which I know monitor current in all phases and will detect a current imbalance and shut down if one leg is not drawing current. Traditional starters may not do this and you can get away with it, although I was pretty certain they all would, because an O/L on one phase without opening the other legs would single phase the motor.

O thats right. I forgot about the phase monitoring on solid state OLs. U can turn that off on some brands though. And most heater/conventional OLs dont have that!

Looks like I need to run a rotary phase converter. The motor on there now is about $2,000 and is a baulder motor. The Maximum amps it requires is 30AMPso I will need to pick one of those up. I can't run a single phase motor on this unit, the magnetic starter is all three phase. To replace that I would be spending a lot of money. The air compressor was a really good but, picked it up for $200.

Also, this will be the only piece of machinery that will require three phase. I don't think down the road we will ever get into machinery.

http://www.ebay.com/itm/5-HP-ROTARY...607?pt=LH_DefaultDomain_0&hash=item45fa633b0f

Bib Overalls: Those looks like really good buys, thanks!

If the motor has an FLA of 30a @ 240v 3phase, then its probably a 10hp motor!!

 

[bannerd]

Ordered me a single phase motor, for the money to do a rotary I would have too much invested. Should be here on Monday, 70lbs electic brute

 

[Norcal]

You may have to replace the mag starter if the existing starter is a NEMA size 1, it's too small for a 5 HP 1Ø motor.

 

[1Garageman]

I think we need some pictures!!!!
The air compressor and the information on the motor!