Can a 3-phase motor runs on 1 phase...

[yusuf]

Can a 3-phase motor runs on 1 phase...

If yes then how !

 

[MikeMl]

No, not without a lot of expense and trouble. It is better to just by a single phase motor with similar power rating.

 

[RODALCO]

Yes.
Two of the motor phase terminals are connected to the Active and Neutral. A capacitor has to be connected between the active and the third phase connection of the motor.
For a 6 terminal motor it is better to start the motor in delta, 3 links applied.
The capacitor value has to be experimented with. about 55 uF per HP.
Cap. Voltage rating at least 400 Volts for a 240 V supply
The motor will run although at less HP.
Look at my YT channel where I have some 3 phase motors running on 1 phase supply.

 

[MikeMl]

Ok, I'll revise my answer: A three-phase motor can be made to run poorly on single phase.

 

[jpanhalt]

1) A three phase motor will run on single phase, but will not self start. Some people who use this method put a knob or sheave on the shaft and roll it with their foot or wrap a cord and pull on it much like you would start a small IC engine. For obvious reasons, many people do not like to kick start a large motor.

2) Self starting is done with capacitors. If you Google on it you will find many plans. Here is one: https://www.metalwebnews.com/howto/ph-conv/ph-conv.html

3) Static converters are sold for running 3-phase motors off single phase.

4) Newer VFD (variable frequency drives) generate 3 phase from single phase electronically and provide speed control. They work great. My drill press and shaper are both run by them. The range of speed is nice as is the power delivered. In fact, I converted the drill press from single phase to 3-phase just so I could use a VFD.

With #1 and #2 it is common to have at least two, three-phase motors. The first motor is an idler and generates the 3-phase current for the other working motor(s). It is not used for powering any tool, usually. The idler motor should be larger than the working motor. If you have many motors in parallel , the largest working motor should not be larger then the sum of the others.

In my shop, I use a 5 HP idler motor to run a 1.5 HP lather and 2 HP mill. The idler is set up as a self start. I have been using that system since 1985. The mill and lathe run fine, even at the same time. I was advised at to outset to use a "heavy iron," older 3-phase motor as the idler -- the type that took of lots of space and needed a crane to move. I couldn't find one, so I just used a modern 3-phase Baldor.

With method #3 the motor can be used for power, but the static converter is expensive. See: **broken link removed** Cedarberg has been around a long time and works well.

Today, I would and do use a VFD running from single phase to run a 3-phase motor in a shop without 3 phase.

John

 

[MikeMl]

And how much does a VFD cost?

 

[jpanhalt]

I got mine on eBay, circa 2004 to 2006. I have two operating on machines and a couple on the shelf. One of those is destined for an older scroll saw. Look for bargains. Like everything (almost) on eBay today, there are mostly retailers at virtually retail prices. Some are even higher.

Look for new. "Removed from operating equipment" may mean it was removed when the equipment stopped operating.

I don't recall the exact prices I paid and can't search that far back on eBay. It is very unlikely I paid much more than $100 to 125 for them. Retail price for a 2 HP unit is now $202 (**broken link removed**).

In my opinion, if you want variable speed and good torque, the choices are 3-phase VFD or DC. Details of the application control that choice. For example, I have another small lathe that is DC. That is because I needed a fast stop and start. The 3-phase converter I made was before before modern electronics. I still use it, because it works, but will probably convert both the mill and lathe to VFD when my move to a new shop is complete.

When you combine the price of 3-phase motors and complete VFD units with the performance they offer operating off single-phase, I just don't think the hassles of single-phase make sense for variable-speed small tools, if you have a choice.

John

 

[picbits]

And how much does a VFD cost?

I use a VFD on my 3 phase 1hp motor to run it from 240v - it cost me £40 delivered brand new but surplus stock.

The motor runs beautifully in both directions with plenty of torque - I can even provide feedback to the VFD and digitally control it.

Now all I have to do is rebuild the lathe I bought it all for and I have a proper use for it .....

 

[KeepItSimpleStupid]

It's very common now to see "three phase motors" operating from a single phase supply, BUT there is a fair amount of electronics between them.

A fancy washing machine is one fine example. VFD drives do it all the time. Single phase in 3 phase motor on the output.

 

[tcmtech]

Yes. I have been doing it for years and here is how.

https://www.electro-tech-online.com/threads/3-phase-converter-schematic-miller-system.100563/