3ph Motor & 1ph Supply

It's not economically viable, also there is very low chance that you will get a single phase motor in 10Hp, best option is upgrade your connection to 3Ph.

As rakesh_semwal says, it is often not economically feasible, but it is possible and it may be feasible depending on the exact situation.

I'm trying to remember the details, but I've seen people make sort of a rotary converter--a single phase motor driving a 3 phase generator to create 3 phase power to run the motor. I've seen hobbyists do this sort of thing, maybe when they acquired a machine of some sort with a 3 phase motor that would be hard to replace (and in a home environment where 3 phase power is expensive to come by).

Look on the internet--maybe search terms like ["3 phase" "single phase" "rotary converter"].

Also, investigate to determine whether you really need 10 hp for your use of the machine--sometimes in a home environment that machine will be used very lightly, and you can get away with a much smaller rotary converter than you'd need for 10 hp (if you can start the motor under no load).

There was / is something else tugging at my memory strings--there is a way to run a 3 phase motor on a 1 phase supply using (one or more?) capacitors. If you search as mentioned in my first post, you'll probably come across it. I don't think it will work for heavily loaded motors.

thanks

I gave you a GA, but the one thing I disagree with is that you don't need a transformer for all solutions. (You didn't quite say that, but that's how I read it the first time, and may appear to others.)

A rotary converter could use a single phase 120 volt motor and drive a 415 volt 3 phase generator. (That might be stretching it--you won't get much horsepower out of a 120 volt motor--240 volt be better--my only point is, you don't have to use a transformer.)

Other than that, some good solutions that I hadn't thought of.

I know it's possible to use an induction motor as a rotary transformer, if that's what you were referring to. But my issue with that was that when someone is unsure of the entire concept of phase conversion, telling them about a very advanced form of it that only the very bold and experienced people attempt was not prudent. But since you let the cat out of the bag, yes, that's possible. It's just not for the novice.

I'm not sure I'm talking about a rotary transformer. I'm just talking about a motor driving a generator (i.e., their shafts coupled together). Let the motor be rated at (and driven by) a 120 volt power source, let the generator be rated at 415 volts.

In a way you are correct but in the practical application the conversion process of independent motors driving independent generators can get physically large and inefficient quite quickly which comes to the horrible end results that its generally a clunky, expensive to build, and not the least bit energy efficient way to do it.

The whole point of my work and development and subsequent posting of my design online for everyone to copy and use freely was to show people how they can successfully run big three phase motors on single phase sources while maintaining normal power outputs and working efficiencies without needing a mass of external components and or additional rotary type converter units.

As mentioned earlier once you get to 10 Hp on single phase those motors get expensive where as a ten Hp multi voltage three phase motor in good used condition can be found for $50 - $100 or less.

I'm going to have to find my Brook Crompton motor reference book it gives the diagram for a rotary phase converter.

Just after I finished my apprenticeship there was a couple of us in the workshop with nothing to do so we decided to entertain ourselves by building a rotary phase converter. Non of us thought it would work, but it did.

OK we had a hefty 240V supply. Once the pilot motor was up and running (it only needs a flick by hand to get it going) we found the more load motors the better the starting of the next motor. We had 25HP of motors running at one point. Then the forman showed up to spoil the fun! It took some fast talking to convince him it was for the benefit of the apprentice that was with us.

10 HP is a big motor; about 10,000 Watts.

The 230V supply must be big enough to supply a converter that will supply at least 20,000 Watts. A dedicated 100 Amp circuit should provide the power.

First problem: What 1 Phase power do you have avialable?

A converter this big will, usually, have to be solid mounted to a structural (usually cement) pad.

Second problem: Do you have such a foundation or will you have to build one?

A 20 HP converter is very expensive (try ebay).

Third problem: Do you have sufficient financial resources to fund such an adventure?

A converter this big is very bulky to transport.

Fourth problem: Since rail would be the most cost effective, do you have access to a siding?

Weighing the associated factors, it would be cheaper, and simpler to just upgrade your service to 3 Phase; however, W.C. Fields said, "We have a moral obligation to separate a fool from his money."

Good luck in the contest!!!!

Why people ask same question again & again?

I built a rotary phase converter from scratch but it was only 3hp. the parts cost about $75.00. The problem is it would blow the capacitors about every couple of months and this got exspensive, even buying them on ebay. to bulid a 10hp phase converter You would need another three phase 10 plus hp motor to generate the three phase needed to run Your 10hp three phase motor. I would suggest getting a

VFD as some respondents have suggested.

oilcan13

it is not suitable to run 3 phase motor on single phase supply,you should buy single phase 10 h.p motor. visit http://tiny.cc/ghqpk here is all about electrical

Short answer, no.

In our steel plant we have a 25T EOT with a main hoist powered by 60HP IM. It is rated for 80amps.In lowering stage ie. 1st and 2nd step the motor is connected 2phase shorted.There is a load brake motor also for counter torque. If you want to connect a 3ph motor to single phase make sure the cable is capable of giving the rated amps. Capacitor start and run IM works on same principle.

It is possible.In this case you have to connect a running capacitor (Cr),but starting torque will drop to 30% of normal value,and power will be reduced to 80% of rated power.

However,if the same starting torque as for three phase operation is required,a starting capacitor (Cs) has to be connected in parallel with the running capacitor.Its capacitance is calculated as Cs=2.Cr (Make sure your single phase supply tallies with the Cr values given below:

Mains supply voltage in V------ 127V, 220V 380V

Capacitance in μF per KW motor power=200μF/KW(for 127v Mains supply); 70μF/KW(for220v Mains supply);and 20μF/KW(for 380v Mains supply).

Your 10hp(7.5kw) motor shall be in this Steinmetz circuit connection.Normally,for a 3phase in delta,U1-W2,V1-U2,W1-V2,while L1,L2,L3 supply is connected to U1,V1,W1.Now for this Steinmetz circuit connection,the delta connection remains the same,but L1 supply will be connected to U1,L2 to V1,while the Cr and Cs capacitors already in parallel should be linked or connected in between V1 and W1 of motor terminals.Start your motor and it will work fine.Note that your L1 and L2 represents your line/neutral single phase supply.Also,380v 50Hz supply can run your 415v,50Hz motor,and 220v,50Hz supply can handle your 230v,50Hz 1ph supply.

Though the capacitor required(high capacitance at high voltages) is expensive.Its not economical for such higher rated motors,but for less than 2kw motors.