Some pearls of wisdom

[greasemonkey]

Taken from a forum where one member is trying to sell a compressor(3 phase)


It could be changed to single fase yes but that means you have to change the motor. The question is can you get a strong enough single fase motor to work on that compressor? Any pics perhaps?

no, 3 phase motors can run on single phase, just wont be as powerful


Thats the problem. So it wont be any good running it on single phase. Best would be to change motor to single phase motor then.

no man hond you dont understand. its just going to take longer to fill the tank. its a compressor unlike a normal e/tool which you need the power to do the work

OK Whatever

on single phase that thing is going to pull lank amps and probably trip the power.

You can go to about a 3kW motor on single phase normal outlet (using the correct curve breaker) before it will trip, more on a welding outlet.

Im kinda thinking a 500l compressor will use more then a 3kw motor. D curve breaker will work you are correct.


And the prize goes to...... (from someone that builds and sell generators for a living?


Running a 3-phase motor on single phase will burn it, no matter what the scientists on this thread say.

Star-Delta starters (to lower start-up amps) start a 3-phase motor by rotating it on single phase and then switching over to 3 phase once peak RPM is reached, this allows less current draw on start-up than normal Direct-On-Line starters (DOL).

You all wanna see what happens when a star-delta malfunctions and it gets stuck in single phase? It ain't pretty.

So hou op kak praat, dit gaan nie werk nie.

[dfsa]

So hou op kak praat, dit gaan nie werk nie.

Gevaarlike Forum wat jy daar het. Enigste ou wat weet wat hy van praat. Hy praat nie KAK nie.

[Martinco]

It is quite obvious the all the fundies on TFSA have been leading us mortals by the nose and caused us to spend thousands on buying new motors when we could have used the old ones in the fashion described above !

Even Eskom can save millions on supplying single phase only. ( Less copper to be stolen as well )

These guys are going to start a new industrial revolution !

On a more serious note. A three phase motor will actually run on a single phase if you connect only one of the phases to 230 v but you have to start the motor by hand ( in any direction ) and the amount of power in very small.
So technically the guy is correct but not practical.

[Dave A]

Welcome to the science of wishful thinking

[dfsa]

On a more serious note. A three phase motor will actually run on a single phase if you connect only one of the phases to 230 v but you have to start the motor by hand ( in any direction ) and the amount of power in very small.
So technically the guy is correct but not practical.

Nou begin ons ook KAK praat: On a technical note: Yes you can run a 3 Phase motor with Single Phase input up to about 2,2KW. You simply go and buy a VSD with SAPWM vector control. These drives take a Single phase 220vac input and supply a 3 Phase 0-400Hz output.

Now back to the KAK praat forum: This guy now need to go and buy this VSD and it should run on his existing motor, but in real terms he should first go and buy another motor 3 Phase 220vac. In that case I would rather go and dump the compressor motor and get a 220vac single Phase motor that can handle the Load.

Ohh forgot, he would not need to go buy a D Curve breaker as he will have a soft start. At least he will safe himself a couple bucks on the CB.

[mikilianis]

Some Info On the subject

Running 3-phase motors on 1-phase Three-phase motors will run on single phase as readily as single phase motors. The only problem for either motor is starting. Sometimes 3-phase motors are purchased for use on single phase if three-phase power is anticipated. The power rating needs to be 50% larger than for a comparable single phase motor to make up for one unused winding. Single phase is applied to a pair of windings simultanous with a start capacitor in series with the third winding. The start switch is opened in Figure below upon motor start. Sometimes a smaller capacitor than the start capacitor is retained while running. Starting a three-phase motor on single phase. The circuit for running a three-phase motor on single phase is known as “ add a phase ” or various other brand names. “ Add a phase ” supplies a phase approximately midway ∠ 90 o between the ∠ 180 o single phase power source terminals.

[Martinco]

Nou begin ons ook KAK praat:

Nie so nie dfsa, ek het dit al op verskei male gedoen. Kyk na pos bo en sien hoe.

[dfsa]

Nie so nie dfsa, ek het dit al op verskei male gedoen. Kyk na pos bo en sien hoe.

Ek Praat maar engels vir ander mense: OK so how long did the motor run after you done the Phase angle and what torque did you manage to get out?

Let us forget at this point about over heating. ( You have a 3 Phase 400vac motor that you now apply 1 Phase 230vac )

[bergie]

regarding star delta. star is 230 volt 3 phase not single phase.

[dfsa]

regarding star delta. star is 230 volt 3 phase not single phase.

Bergie you need to read tha whole post Mate. Just a note: Are you sure it is not perhaps a 400/660 motor? Oops there go the 230vac Star connection.

Some Info On the subject

Running 3-phase motors on 1-phase Three-phase motors will run on single phase as readily as single phase motors. The only problem for either motor is starting. Sometimes 3-phase motors are purchased for use on single phase if three-phase power is anticipated. The power rating needs to be 50% larger than for a comparable single phase motor to make up for one unused winding. Single phase is applied to a pair of windings simultanous with a start capacitor in series with the third winding. The start switch is opened in Figure below upon motor start. Sometimes a smaller capacitor than the start capacitor is retained while running. Starting a three-phase motor on single phase. The circuit for running a three-phase motor on single phase is known as “ add a phase ” or various other brand names. “ Add a phase ” supplies a phase approximately midway ∠ 90 o between the ∠ 180 o single phase power source terminals.

I don't think the person or yourself have tryed to modify a Motor like that. Firstly you would need to do some intense calculations to select the correct capacitors. Now you need to add the cap switch and disconnect the start cap at the right time. You also most probebly will have to select a F class motor ect. Now you switch on the power and find the motor is unballanced. Just maybe the cap also go pooof.

Nie so nie dfsa, ek het dit al op verskei male gedoen. Kyk na pos bo en sien hoe.

Dude no disrespect, but I really would like to see a 2.2kw motor run like this at capacity. It will run with no load, but sorry not at full load. I would like to know what you did about the Heat. Your motor will cook in no time.


This looks like a problem that many people might have "Single phase supply with Three phase equipment" Hmmmm maybe there is money to be made here.

[AndyD]

I have a circuit I've designed over many years in conjunction with a group of Nigerian scientists. It consists of a network of tri-evelonic capacitators wired in serallel with a power kiac output stage. The box it comes in is about the same size as a cigarette carton and it's potted in high MPA concrete to help with the heat dissipation. You connect this circuit to any 3-phase motor and it will then run from either a 5 Amp single phase supply or you can insert 3 AAA batteries to make the whole system portable for approx 4 hours run time on a sunny day.

I don't want to confuse you with technical issues but in laymans terms it fools the 3-phase motor into thinking it can run on a single phase supply that any fool might know is too small and it fools the batteries into giving around a thousand times their normal output.

We finished field trials of the system last year with the Syrian military and they've endorsed the product wholeheartedly. Send me a pm and I'll give you my off-shore account details. When your payment R2500.00 has cleared I'll send it to you by Shaunhigley Couriers.

[dfsa]

Hi Andy

This thread have my upstairs matter smoking here. There is definitely some money to be made from this.

A 1/3 VFD will cost about R2500-00. What you guys designed there looks impressive. What is the output capacity?

A home DIY guy will need to run at least 2,2-4kw standard equipment.

[greasemonkey]

Love the replies - the solutions posted by the guys in the forum that I copied and pasted from do not imply any kind of intelligent solution, and the depth of knowledge is scary however they insist they know all! An example is the character that says 3 phase star uses only one phase.Scary stuff
AndyD, love your design , is the cigarette carton 419 cigs or ponzi cigs? and does the unit fit in automobile apps and if so will Higley couriers drop it into the engine bay(for a fee of course)

[Martinco]

Dude no disrespect, but I really would like to see a 2.2kw motor run like this at capacity. It will run with no load, but sorry not at full load. I would like to know what you did about the Heat. Your motor will cook in no time.

If you look at my post #3, you will see that I said " with little power".
I agree with you that there is no way that you will get 100% power connecting this way.
All I am saying, is that the motor will run.

I did this with a 1,5 Kw motor not so long ago ( No caps or anything else ) and put this onto a wood lathe to polish and do small cuts on things like broom handles etc. ( No tree trunks )
I only connected one of the windings ( Delta ) to 230V and had to spin the motor by hand to get it started.
As far as heat was concerned on this.......virtually nothing.
If you do not believe me, go try !

[dfsa]

If you look at my post #3, you will see that I said " with little power".
I agree with you that there is no way that you will get 100% power connecting this way.
All I am saying, is that the motor will run.

I did this with a 1,5 Kw motor not so long ago ( No caps or anything else ) and put this onto a wood lathe to polish and do small cuts on things like broom handles etc. ( No tree trunks )
I only connected one of the windings ( Delta ) to V and had to spin the motor by hand to get it started.
As far as heat was concerned on this.......virtually nothing.
If you do not believe me, go try !

Well exactly, nobody said the motor will not turn at all. Thing is you can not tell a person that it will work. Your motor basically did a free no load spin.

The original question was "Can I run my 3 phase compressor motor from a single phase supply" Fact No!! Based on what you said this guy will now actually go and do it and injure himself.

Go start that motor again, then put proper load on it and see what will happen. Then stop it and start it again later. Go do this for a couple days if you are lucky to get past the first day. A motor running free with no load is useless to anybody.