Largest Motor

!0,000,000 000kW, as long as you have enough current available.

All kidding aside, Voltage means nothing, the amount of available current is the determining factor.

look at the online motor catalogs. You will see that the multiphase dominates the higher powers. From the catalogs you will see where they stop the single phase.

They do this because the greater efficiency of 3 phase becomes impossible to ignore at higher powers.

efficiecny =$$. If you were to compare the efficiency of a custom made 10,000 HP single phase motor with a 3 phase machine, you might find that 10,000HP = 7500 KW x 24 hours = 180,000 kilowatt hours per days, at 5 cents per KWH = $9000 per day.

If the 3 phase is 96% efficienct and the 1 phase = 91% = $450/day or $164,250 per year.

Google motor prices, you might find this extra efficiency is a powerrful motive for three phase motors...

As far as I know, the largest single phase motors are usually in the range of some 10-15KW only.

In addition to above- efficiency etc, there is another limiter- the starting - whethet it is capacitor, split pole or whateever- the starting circuit for the large single phase motors are going to be a real PIA.

Thank you for sparing your time to share some views. Jerry New Hampshire's reply(below) is also good.

Regards,

prashanth

india

I had running a 3,5 kW motor with no problems. The main issues are related to the electric company on one hand (they allow a maximum single phase load) and to the grid on the other hand because of the unbalanced load (which goes back to the electric company)

Thanks for the reply sir.

Its a very good reply. I agree 100% with you that one of the phases gets loaded, as the rating increases.

Regards,

prashanth

Hi prashanth,

230V without stated current. Say 15 A (the big pin power point ex Raj), then 3450VA is available continiously,with some more during starting surges. A 2 hp motor direct on line started, is just about all you can use.

If you want more, you can power factor correct and a 3 hp motor could be used with about 70 microfarads of 250 V a.c.continiously rated capacitors across the line. To limit starting surge current it would be appropriate to start unloaded (belt slackened or clutch disengaged) if possible. A series resistor starter using stove elements could be used, shorted after mitor speed reaches about 60% of full.

if you look at the nameplates of inverter type airconditioners note that they have almost 100% power factor, i.e. voltage X current = watts. Using an inverter of the unity input power factor type you eliminate starting surge and reactive motor power, so you an use up to a 4 hp motor on that power point. By the way the inverter drives a, much cheaper, 3 phase delta connected motor so saving some of the inverter's cost.

Regards,

Zaf.

In the UK you have 13 amp ring mains, here in Germany 16 Amp spurs...

Therefore the theoretical largest motor for the UK will bee 240 x 13 = 3.12 KW for Germany. For the UK it will be 240 x 16 = 3.84 KW.....

You must always also remember that induction motors take large currents on startup, so you will need to take this into consideration, even single phase ones, so if you are being careful and cheap, you need to divide the current by 6 (approx) as such motors take 6 x the running current on start.....or you need to reduce current with a reduced current starter.....your decision! If done correctly, you might be able to use a motor that takes 1/2 the allowed current......

What are the laws/standards in your country?

You just need to substitute the values of voltage and maximum current for your country/area....and divide by 6 or so.......

A quick perusal of some motor catalogs shows me a 10 HP maximum for single phase 220VAC.

For the most part 10HP (SAE) is about the max you'll see single phase. I did see a 15HP single phase motor once but it had something like a 65 amp draw@240V. Not too practicle, to go very large on single phase.

Limited by the single phase motors you can buy. 10 hp is about tops

IE present rules do not allow single phase motor of more than 2.0 HP

Here in the states, in residential as well as some commercial/light industrial, we quite often do not have the option of getting 3 phase power supplied. So, we tend to have much larger single phase motors than 2HP.

Yes any HP motor can be on single phase, but blogger is from India. In India it was 5HP max. earlier, but now it is 2HP.

Some ideas:- in some Indian villages Govenament to restrict use of 3-phase pump motors during peak-load timings feed same phase in all three phases. They distribute power in such a way that one village get one phase and distant other village gets other phase and so on. So that people get lights but can not run 3-phase loads. There some wise people who purchased single phase input and 3 phase out put VFD's and happily run 3-phase pump sets.

I never knew that India limited 1 phase motors like that.

You learn something new every day.

Thanks

Ian