Phase Conversion

Here are some ideas.

Phases lag 120degrees of the angular speed in a 3-phase system. A capacitor'c current lags the voltage 90 degrees. So it is impossible to achieve a viable 3-phase circuit from a 2-phase one using capacitor, because appliances are designed for 120 degree 3 - phase supplies. If we had 4-phase supplies, that would have 90 degrees phase lags, then it would be possible to make suchlike experiments.

yes i understand ..can we do without condenser........?

There are VFD's turning a 2-wire voltage into a 3-wire 3-phase voltage. At least I know drives converting 1-phase 220 V into 3-phase 220V.

ok fine.....if u have given a 2 to 3 phase converter then how would you test it.......?

i have one 2 to 3 phase converter whose input across the two wire is 415v then i should get the 3 phase output with 415v at each phases but i am not getting across L2 (yellow) phase were as for other phases i am getting 415v.

can you tell me what is the problem and how can i rectify it?

1-phase to 3-phase inverter. If there are ones for 415V , then one turning 1-phase 415V into 3-phase 415V. You will know there are 3 phase 415V measuring voltage output across any of the 3 phases: there should be 415V everywhere.

could you post the pic?

too lazy to register over there

Not really too lazy to post as well plus clicking on the link should have taken you there directly to view as a guest unless they changed something I am not aware of.

Nope. I could not get there either without registering.

you brought the text

but the schematic didn't make it

It shows up on my computer at the bottom of the text.

That's probably because you are logged on to the site.

Clicking on the little box at the bottom of your text takes us to the login page.

Hi Rimpul,

you can run a 3-phase induction motor from 2-wire AC. Connect 2 wires from the motor to the mains. Connect a capacitor from the remaining motor wire to one of the mains wires. For the capacitor use about 70 microfarad for every kilowatt specified for your motor.

You fool your motor with an asymetrical 3-phase system, so you get less power and torque, especially starting torque. It's OK for pumping. This scheme is extensively used by rice planters.

For safety: use a metallized (self-healing) polypropylene capacitor with a metallic housing, with overpressure disconnection and discharge resistor (single phase, 480 V or more). Discharge may take some minutes, so short the cap before handling it.

Your motor will heat more, too.

Start experimenting with smaller motors (< 1 HP or so). Cut and try. Some people use an additional capacitor for starting, this may be a sarting (lectrolytic) cap.

This scheme should work with other 3-phase loads, but then there might be other solutions,

brgds

Snel

thank you for your reply..

but sir i dint understand about this point "Connect a capacitor from the remaining motor wire to one of the mains wires." do u mean i should connect both the ends of the capacitor to the remaining phase terminal of motor..

regards

rimpul

Hi Rimpul,

The three phase power capacitor will be Three terminals. Connect R and Y terminal in the capacitor (Imaging B is absence now). connect the motor terminal also R and Y and connect the B terminal of the motor to the Third terminal (B) of the capacitor.

Hope now you understand

regards

Ravi-Coimbatore

thanks ravi..

do u have pic of the capacitor or part no. so that i can download the datasheet.

brdgs

rimpul.

Dear Rimpul,

you can have a suitable capacitor from Epcos (they have a factory in Nashik):

http://www.epcos.com/inf/20/50/ds/b32340_c.pdf

you'd better use a single phase capacitor (2 ends) for this purpose, e. g. B32340C. A three-phase one as suggested by Ravi is a little more complicated to connect (3 ends) and offers lower benefit vs. cost in this specific application (maybe it's easier for you to find).

So you connect one end of the capacitor to the remaining phase terminal of the motor and connect the other end of the capacitor to one of the mains wires. Which one of the mains wires? Try one of them, in case the motor runs the wrong direction you will know you have made the wrong choice... And please make sure you discharge the capacitor everytime you touch it. I have to agree with Andy's advices.

Andy, thanks for your comment, I've pre-marked my post as off-topic because the 120-0-120 thing has nothing to do with Rimpul's question.

brgds/mfG

Snel

dear snel.

thanks for your valuable suggestion....but the pdf what you have attached its locked...can you pls give the password to unlock the pdf file.

regards

rimpul

Hello Rimpul,

sorry, I don't have a password for that.

Try looking at

http://www.epcos.com

product catalogue

capacitors

capacitors for power factor correction

PhiCap

data sheets

PhiCap 1-phase

best regards

Snel

thank you snel.

regards

rimpul

Here's the freq drive solution

http://www.automationdirect.com/adc/Technical/Catalog/Drives/GS2_(115_-z-_230_-z-_460_-z-_575_VAC_V-z-Hz_Control)/GS2_Drive_Units_(115_-z-_230_-z-_460_-z-_575_VAC)

open the 2nd pdf GS2 variable frequency drive specs

There is a misunderstanding topped by miscommunication in the original question. I have found no true 2 phase power anywhere in the world. It is one phase for household use (mostly) or industrial 3 phase for motors (mostly). This is oversimplification, but will serve. There is a weird use of power and language in USA. The kilovolts distribution system is always 3 phase. In residential use a single phase transformer is connected to one of the 3 phases. The secondary provides a center tapped 220V, where each half is 110V, exactly 180 degrees to each other, and called in the trade language 2 phases. The hell it is. It is sloppy misuse of the language.

You CAN make three real phases from one, sort of, as the previous note #8 mentions. But it is a cludge. I would use it in a garage workshop, as the township will not give anything but single phase. In industrial setting it is unacceptable, will not pass inspection.

For commercial use there are rotary converters and solid state converters, all type approved. If you need instant direction reversal - as with a lathe - have 3 HP, but preferably 5HP converter for every HP driven.

But, for industrial use in industrial zoning you automatically get 3 true phases.

[quote]The secondary provides a center tapped 220V, where each half is 110V, exactly 180 degrees to each other, and called in the trade language 2 phases. The hell it is. It is sloppy misuse of the language.[/quote]

Why do you say 110 and 220, when when it's 120 and 240? I'm not saying that your wrong, it's just that I see this all the time and I'm asking you. :)
Sorry for OT.

Yes, you are right. Nominal 110V is mostly 120V, and so on. Since I am the closest to the transformer in my street, I had real problems with the voltage at the beginning. Learned quickly, to buy 120V lightbulbs and such. At the end of the streets my neighbours have maybe 100V. The blessings of an antiquated low voltage single phase service.

I have a bet with you. People will come back, again, persisting in the 2 phase nonsense. It seems to me, some insist to let it hang out. Not a pretty sight.

I used to work at a 64 lane bowling alley

the voltage was around 130volts, no light bulb was safe, the utility had hooked to the wrong tap on the transformer, once we got them to change it so we had 118v,

the boss complained about how dim the lights were

you're right about the 2 phase

another one that will mess you up is 3 phase with the stinger leg, older equipment doesn't much care for 208 being used for control power...

On one phase connect thru series capacitor to give 60 degree phase change. On same phase, connect series inductor to give 60 degrees phase change in the opposite direction. You now have 3 phase, 120 degrees between phases.

To calculate approx value of cap and inductor,

- work out approx "resistive" value of each phase of the load under normal operating conditions,

- draw phase diagram to work out reactance value required (or use calculator),

- use reactance formulae to give values of cap and inductor.

Those values will only work for that particular load. Of course if the load is a motor, start up will be interesting, because the phase angle changes will be larger with the lower "resistive" load. There won't be great starting torque. Once running at normal speed and constant torque, fine.

This is not a great solution, but ...

i have heard of using a two phase motor to drive a three phase motor. it's my unstanding that the driven three phase motor will produce three phase power.

There are really no 2 phase systems, the US system for 220 volts is actually a single phase, a tap in the middle for 110 volts.

So its either a single phase or a 3 phase......

An add-on to #15. In the antiquated single phase system a 110V +/-10% = 20V deviation is deemed acceptable. IMHO in modern times it is not.

Let's compare it with a semimodern 220V(240V) three phase system. (Modern would be 380V or 450V, but it is for another time).

If a certain kilowatt passing thru causes 10V drop in a single phase, the same kilowatt causes 5V drop in a 220V single phase, causes (approximately, as power not always evenly distributed), 5/3 = roughly 1.6V drop in three phase. What is the % value?

Going from 110V single phase to a semimodern 220V three phase reduces troublesome voltage variation from +/-10% to a trivial +/-1,6%.

There. What does it cost? Changing the ancient local code. Replacing single phase transformer in future installations and replacements with smaller, and lighter three phase ones. Replacement breaker panels in three phase. Who cares, costwise?

Dear Rimpul,

I am sorry to have to say this, but by the quality of your questions it indicates to me that you are not electrically "au fait" with such work as needed on this blog. This does mean that you may cause a fire, kill someone, or even kill yourself......

You need someone to help you that is at least a trained electrician......

Always remember - !SAFETY FIRST! -