Can anyone tell me if what I'm trying to find is impossible.

We need to run three 20HP (Twenty) 3 phase 50 amps motors for a water pump application. These pumps will run for two minutes intermittently.

The problem we are havin right now is the outrageous cost that the Electric Company charges to install 3 Phase electricity in our area.

Question One: Do you guys/girls know of any Motor Driver-Inverter that will run these motors with a 240vac single phase input?

Question Two: Can we run these motors with a Phase Converter. Are they reliable?

Thanks

Mr. Anibal Hernandez
Piscis Automation
San Juan Puerto Rico.

 

You can use the 240 single phase to go to a 3 phase drive but you will have to de-rate by 1/3

 

Maybe someone else knows of a brand that can handle up to 20 HP motors, but the only VF drives I've ever seen that can operate on single-phase input power are all under 5 HP.

 

Eylander Electric 425 259-1601 has a Rotary Phase Converter 1/2 hp to 150hp. UL listed runs 3phase electric motors on 1 phase. 5 year warranty meets 2002 electric code.

 

My company manufactures skid mounted pumping plants, so we come up against your problem frequently.

First, what is outragious? After you purchase a 1 phase solution, you may decide that the 3 phase solution was not so expensive.

Second, ask around and find someone who is good at dealing with the Power Company. Sharp electricians often know how get them to put the 3 phase in without the high cost. Also consider going to the government agency that controls the power provider.

If you must go single phase here are your options, and I personally have gone down every one of these roads out of necessity.

1. GE will provide a 40 hp drive to run your 3 phase 20 hp pumps on single phase source. You will have to disable overload and phase imbalance settings in the software to work properly. Then you just install overloads separate from the drive.

2. Install more and smaller pumps that will run on single phase directly. 10 hp is the largest for horizontal centrifugal pumps. These pumps have more problems than 3 phase due to their starting switches. Definitely avoid using these if jogging or frequent starts is a requirement.

3. If you can use a submersible turbine, Franklin makes a beautiful 1 phase 15 hp submersible motor. We make our own above ground submersible pump systems with the Franklin 15 hp motor by sealing the turbine in a can ourselves. And you may get by with 15 hp because turbines are often more efficient than centrifugals, if that is what you are using.

4. Rotary Phase converter is of course workable, but extra controls are required, and now you have more equipment to maintain. Rotary phase converters are like motors also, avoid using them in hot or wet environments.

5. There are manufacturer's of large single phase motors, but I have never used one and do not know how they work out. I have seen up to 100 hp single phase motors.

SUMMARY - Use the 15 hp Franklin submersible motors if possible. We have had absolutely no problem with them. But we make our own starting systems for these, and that helps also.

Richard Neff
pump @shadow.com

 

> Can anyone tell me if what I'm trying to find is impossible.

I suspect your requirements can be met but you beg the real question, "Is it economically viable?".

> We need to run three 20HP (Twenty) 3 phase 50 amps motors for a water
> pump application. These pumps will run for two minutes intermittently.

Let's run a sanity check on your numbers:

Calculating theoretical values first,

20 HP * 746 Watts = 14920 per motor or 44760 Watts total

Now add real world,

44760 watts/ .8 (motor & conv efficiency) = 55950 watts

at 240 VAC = 233.125 amps

and double for starting surge = 466 amps demand

Now contact your power company and tell them you have a 466 amp demand at something like a .8 power factor that only runs for 2 minutes! Tell them how outrageous you think their 3 phase quote is and see how outrageous their single phase quote is. (I'd do this over the phone so my body, except for my ears, would not be in jeopardy.)

> The problem we are havin right now is the outrageous cost that the
> Electric Company charges to install 3 Phase electricity in our area.
>
> Question One: Do you guys/girls know of any Motor Driver-Inverter that
> will run these motors with a 240vac single phase input?

Yes there are converters or motorgen sets that could do the job but they are made to order, not off the shelf. If you have not already purchased your motors I would consider DC motors. Ship propulsion DC motors will probably be cheaper and
use a simpler converter design.

> Question Two: Can we run these motors with a Phase Converter. Are they
> reliable?

Yes but not cheap.

Fred Townsend
DC to Light Consultants

 

AC Tech offers drives that can be run off single phase sources, but not sure if they have anything in the HP range you are looking at.

There are other ways to solve this problem, but it may turn out that to pay the "outrageous" price demanded by the utility company is the least expensive one over time.

60 HP at 240V single phase is a LOT of juice (like almost 300A).

 

The answer to both questions is an emphatic... yes! However, I strongly recommend that you investigate the viability of the single-phase source capability to run some 60-Hp load. I would also question the intermittent duty you cited.

Additional information from you might elicit additional List response.

Regards,
Phil Corso, PE
(Boca Raton, FL)

 

Most single phase motors are all under 7.5 hp for the simple reason that most utilities will not allow users to install motors of more than 7.5 hp on a single phase system. This is because of the imbalance that this high load can create on the distribution network.....a nightmare for the
hydro guys and your neighbors!

Gerald Beaudoin
Automation Systems Specialist
Leahy Orchards Inc.
1772 Route 209
Franklin Center, QC.,
J0S 1E0
450 827 2544, ext 201
450 827 2470, fax

 

Most single phase motors are all under 7.5 hp for the simple reason that most utilities will not allow users to install motors of more than 7.5
hp on a single phase system. This is because of the imbalance that this high load can create on the distribution network..... a nightmare for the hydro guys and your neighbors!

Gerald Beaudoin
Automation Systems Specialist
Leahy Orchards Inc.
1772 Route 209
Franklin Center, QC.,
J0S 1E0
450 827 2544, ext 201
450 827 2470, fax

 

I have found the correct values for running three-phase 240 volt motors on single-phase to be 50 microfarads per horsepower. Simply operate one 20 hp three-phase motor on single-phase feeding T1 and T2 with 240 volts with the MOTOR RUN OIL FILLED capacitor rated 280 WVAC (working volts AC) between T2 and T3. This "IDLE" motor will slowly start and run. When this "IDLE" motor is up and running you can run up tp (4) 20 hp motors from this induction generating phase converter. You must keep in mind that all this power is coming from the single-phase source so power it accordingly. We have done this a couple dozen times and all those units are still alive and well. Using the above values the voltage under load will be within about 2 volts phase to phase to phase. Well, that's it, good luck.