Previous in Forum: Groundig Resistance   Next in Forum: Energy Meter Show Different Current on Different Phase
Close
Close
Close
10 comments
Rating: Comments: Nested
Active Contributor

Join Date: Sep 2010
Posts: 20

Electrical Wiring

11/14/2012 9:10 AM

when R & Y phase short together then there will be firing, short circuit or over heating in the circuit but when these two phases are applied on two terminals of 440 V coil of a contactor, coil is energized and contactor works but there is no fire or no short circuit. how is it possible?

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

"Almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, vote them!
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#1

Re: electrical wiring

11/14/2012 9:15 AM

There's somewhere for the power to go, so it can't make the magic smoke.

Register to Reply
Guru

Join Date: Jun 2007
Posts: 1035
Good Answers: 40
#8
In reply to #1

Re: electrical wiring

11/15/2012 9:20 AM
Register to Reply Score 1 for Good Answer
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#10
In reply to #8

Re: electrical wiring

11/15/2012 9:46 AM

Or, more likely in this particular case:

Register to Reply
Guru

Join Date: Aug 2007
Location: Earth - I think.
Posts: 2143
Good Answers: 165
#2

Re: electrical wiring

11/14/2012 9:45 AM

AC impedance.

__________________
TANSTAAFL (If you don't know what that means, Google it - yourself)
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#3

Re: electrical wiring

11/14/2012 9:45 AM

Electricity For Beginners is down the corridor, third door on the right. No, not that one, the next one. That's it. Cheerio.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply Score 1 for Good Answer
Guru
United States - Member - New Member Engineering Fields - Power Engineering - New Member

Join Date: Sep 2006
Location: California, USA, where the Godless live next door to God.
Posts: 4665
Good Answers: 804
#4
In reply to #3

Re: electrical wiring

11/14/2012 12:21 PM

"Electricity For Beginners is down the corridor, third door on the right. No, not that one, the next one. That's it. Cheerio."

No, that door leads to the Abuse Clinic. If you want E.F.B. it's across the hall on the left, right next to Arguments.

http://www.funnyordie.com/videos/be76d3ca8d/argument-clinic-from-monty-python-from-greatest-comedy-sketches

__________________
** All I every really wanted to be, was... A LUMBERJACK!.**
Register to Reply
Guru

Join Date: Oct 2009
Location: sometimes Wales,UK.. was Libya, now Oman!
Posts: 1715
Good Answers: 117
#5
In reply to #4

Re: electrical wiring

11/15/2012 1:31 AM

and there I was thinking it was the other door, "How to do your own homework!"....

adityaEI.... sorry my friend..... my question for you is, "could your teacher not help you?"

__________________
The square root of nothing is what you make it!
Register to Reply
Active Contributor

Join Date: Sep 2011
Posts: 14
Good Answers: 1
#6

Re: Electrical Wiring

11/15/2012 7:56 AM

The Coil acts as a load. The contactor develops the heat which is comparatively less than the SCC heat.

Register to Reply
Commentator

Join Date: Aug 2012
Posts: 68
#7

Re: Electrical Wiring

11/15/2012 8:58 AM

All coils that work at A.C source(like coils of contectors ,motors..etc) have an impedance this impedance is like the working of a resistance in d.c circuit.and also has the same unit (ohms) and you can calculate it by use the OHMS LOW.

imped.= Va.c/Ia.c .which Va.c ,Ia.c are the components of the voltage and current .

Register to Reply
Power-User

Join Date: Sep 2008
Posts: 196
Good Answers: 6
#9

Re: Electrical Wiring

11/15/2012 9:43 AM

When two phase conductors are shorted together the only impedance/resistance available to limit the current developed in the established circuit is the very low impedance of the conductors.

Therefore the amount of watts/heat produced by the current flowing in the circuit is only limited by the power available from the voltage source. (Transformer, generator, battery,etc.)

This large amount of energy/watts/heat must be dissipated by the connection and the conductors.

Since the shorted connection is usually the weakest point in the circuit the failure normally occurs at the connection resulting in an arc flash/explosion.

When the conductors are attached to the coil the coil conductors in combination with the pole piece present impedance/resistance to the current flow thereby limiting the amount/magnitude of current produced in the circuit.

The energy produced is converted into magnetic flux allowing the power to be dissipated without causing a failure of any component in the curcuit.

Simplified theory:

E=IR (Ohm's Law)

I=E/R

If E = 440 and R = 1 then I = 440 amps and P = EI = 440 x 440 = 193,600 watts

If E = 440 and R = .5 then I = 880 amps and P = 387,200 watts

If E = 440 and R = 50 then I = 8.8 amps and P = 3,872 watts

If E = 440 and R = 500 then I = .88 amps and P = 387.2 watts

This is a very simplified explanation that in no way takes into account all aspects of AC theory and if you want to understand better it is important that you study/review basic AC theory in depth.

Register to Reply
Register to Reply 10 comments

"Almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, vote them!
Copy to Clipboard

Users who posted comments:

brich (1); caeser (1); GURUMOORTHY (1); JRaef (1); Kilowatt0 (1); lyn (2); ndt-tom (1); PWSlack (1); SHOCKISCAN (1)

Previous in Forum: Groundig Resistance   Next in Forum: Energy Meter Show Different Current on Different Phase

Advertisement