2 phase question 2

[ketaciturn]

Maybe this question is a little bit too basic for u guys, but please help this poor little kid---me!!

What's the diffrent between 2 phase 200VAC and single phase 200VAC?
If i have a voltage stabilizer which requires 200VAC single phase supply, can i supply it with 200VAC 2 phase supply?
The stabilizer is going to connect to PLC works in 100VAC (Of cause the voltage stabilizer has 100VAC output...)

Thanks...

 

[busbar]

Would you elaborate on your term "200VAC 2 phase supply"? What are the voltage relationships and angles in this configuration?

 

[dydt]

hi...
there is always a misconception that if there is two hot line(220V)...it is called 2 phase..this is very common esp. to those who doesnt have any background on voltage/current phasors...lots of times i hear this from electricians..and if you start explaining the phase differences ..etc...its get more confusing to them..

perhaps you are dealing with 200v and 100v single phase....is this is a Japanese equipment?

dydt

 

[ketaciturn]

sorry for confusing u guys, i think i better clearify something...

the PLC is using 100V single phase as input.
and the
stabilizer is using 200V single phase as input, and its output is 100V single phase.
The power source that i have is a 200V 3 phase.
So, what i meant was, is it possible to take 2 line (R,S) from the 3 phase 200V to supply the stabilizer(which required 200V single phase supply)?



3phase
200V
60Hz __________ _____
R--------| |-----| |
S--------| stabilizer |-----| PLC |
T---- |__________| |_____|
(supply)

Hope the diagram helps to clear things up a little..

 

[Bung]

Let's keep it simple and not confuse "phases" and "phasors". Your voltage stabiliser requires 200Vac to ba applied between its two input voltage terminals. All you need to do is find a source which will give you 200Vac across two of its output terminals. Then take care of the safety earthing things, an you are in business.

Bung

 

[ketaciturn]

u r right Bang, this is what my question is actually...

For a 3 phase 200V supply (let say R,S,T), the voltage across any 2 lines (R,S or S,T or T,R) is 200V right?
Instead of using a single phase 200V power source, can i use the "2 phase" 200V(R,S)(which is tapped from 3phase 200V)?
And what will be the effect of doing this?

busbar, dydt, and Bung, thanks for the responds!!!
And i would like to appologize here if i'm giving too much trouble to u...

 

[Graeme38]

In the UK we use single phase 220V supplies. Three phase suppies are rated at 440V.

I know in the American continent it is common to use bi-phase supplies from a 120V ph-n system to achieve 220Vac. This is a method of wiring not considered acceptable in the UK.

Over the years I have used UK standard equipment 220Vac single phase, and found that it has worked satisfactorily on a bi-phase arrangement in South America. You can run into a little trouble with UPS equipment because it looks for a neutral earth voltage of no greater than 2V. With bi-phase the return conductor is obviously not at zero volts potential, so it will flag up an error. You wold have to read the documentation or speak to the supplier of the PLC to confirm.

As commented by Bung. I think you would have to be careful with the earthing.

 

[busbar]

ket—

For a 3 phase 200V supply (let say R, S, T) the voltage across any 2 lines (R, S or S, T or T, R) is 200V right?

The terminology is sometimes confusing, but tapping 2 wires from any other circuit would be coorectly termed single phase, regardless of the 2-wire connection served ø-ø or ø-n.

 

[ketaciturn]

i think the configuration should be ok.
thanks guys...

 

[jbartos]

Suggestion: The block diagram uses single phase (R,S) of three phase power supply. It needs protection in each line conductor, i.e. R and S, since it is not true single phase power supply that may need one fuse or breaker in one wire only.
The two-phase versus single-phase difference would be such, in view of your block diagram, that all three conductors would lead to the stabilizer for the two-phase power supply; however, the load would be between either R,S and S,T but not between T,R; or between S,T and T,R but not between S,R, or between T,R and R,S but not between T,S.

 

[ketaciturn]

jbartos,

"since it is not true single phase power supply that may need one fuse or breaker in one wire only."
can u please elaborate on this.....thanks.

How if i just use 1 breaker for the two wire R,S before and after the stabilizer??

 

[ketaciturn]

sorry, i got what u mean already...
just forget about the previous post.......sorry..

 

[jbartos]

Suggestion/comment to ketaciturn (Electrical) Jul 22, 2002 marked ///\\jbartos,
"since it is not true single phase power supply that may need one fuse or breaker in one wire only."
can u please elaborate on this.....thanks.
///True single phase power distribution system, e.g. 220V, 1-phase, 2-wire system, has 1 hot wire which is the phase wire and the neutral wire (which is also grounded). Therefore, one protective device in the hot (phase) conductor is used only. However, you cannot use this one for the normal three phase power supply. You would have to apply a transformer with neutral that would be grounded.\\How if i just use 1 breaker for the two wire R,S before and after the stabilizer??
///One breaker poses an insufficient protection for two hot wires that your system has. You could potentially use one breaker on the stabilizer output, if one wire is allowed to be grounded by the stabilizer manufacturer. Ultimately, the best approach is to contact the stabilizer manufacturer tech support regarding your questions and design.\\

 

[ketaciturn]

jbartos,
yupp, u r right. Eventhough i got what u mean already, thanks for further elaborating it!!
Thanks alot for ur kindness and effort!!