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Anonymous Poster #1

Correct Delta Connection

11/30/2016 3:27 AM

Which is the correct delta connection? Left one or Right one. If wrong connection is used, what will happen?

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#1

Re: Corrrect Delta Connection

11/30/2016 3:29 AM

Try doing your own homework

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Anonymous Poster #1
#3
In reply to #1

Re: Corrrect Delta Connection

11/30/2016 4:58 AM

After some study, I find that the energizing of winding may not be in proper order with the right side delta connection causing some high currents during starting, although with both connection motor rotates in the same direction. Is my understanding right?

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#4
In reply to #3

Re: Corrrect Delta Connection

11/30/2016 5:02 AM

The drawing still cannot be read properly.

Is there a prize for getting it right?

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#2

Re: Corrrect Delta Connection

11/30/2016 4:32 AM

Neither, as the drawing cannot be read properly.

Is there a prize for getting it right?

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Anonymous Poster #1
#5
In reply to #2

Re: Corrrect Delta Connection

11/30/2016 5:12 AM

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#6

Re: Corrrect Delta Connection

11/30/2016 5:17 AM

<...If the wrong connection is used...> a circuit protective device will open the circuit.

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#9
In reply to #6

Re: Corrrect Delta Connection

11/30/2016 8:36 AM

or maybe the 3 phase things on your system will run backwards

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#10
In reply to #9

Re: Corrrect Delta Connection

11/30/2016 9:13 AM

...which isn't <...wrong...>, merely inconvenient.

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#11
In reply to #10

Re: Corrrect Delta Connection

11/30/2016 9:30 AM

I agree...

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#17
In reply to #9

Re: Corrrect Delta Connection

12/01/2016 12:32 PM

GA for the best answer reading down from the top. You beat me to it!!

Thats what could happen and swapping any two connections will fix that of course!!

Also, there is test equipment around that will check "the direction of rotation" before damage is caused!!! If he has the sense to find it and use it!!

This original poster demonstrates a singular lack of understanding of 3 phase power!!!

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#8

Re: Corrrect Delta Connection

11/30/2016 8:34 AM

You need to work out the relationship between the three windings

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Anonymous Poster #1
#12

Re: Corrrect Delta Connection

11/30/2016 12:40 PM

I'm sorry I haven't framed the question right. Actually I asked this question in context of open transition star delta switching. During the transition to delta, one type of connection produces less transient current than the other type. The question is why one type of connection produces less transient current?

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#13
In reply to #12

Re: Corrrect Delta Connection

11/30/2016 2:04 PM

Think about why a star-delta starter is used and you will have answered your own question, Mildred.

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#14
In reply to #12

Re: Corrrect Delta Connection

12/01/2016 8:39 AM

While this does have the stamp of homework firmly embedded on it, it is an intriguing question for someone in the US who only sees autotransformer reduced voltage starters, and they are rare, as they should be.

I'm sure you also need to know the coil connections & phase rotation when in star, to answer the question?

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#18
In reply to #12

Re: Corrrect Delta Connection

12/01/2016 12:39 PM

I would wonder.....

1. If different connection gives different transient peak every time - because there are always random phase timing differences between each moment you press start. A voltage zero at main contact close always gives worst transient - timing is different for each phase always.

2. If the control voltage phase is altered when transfo connection is changed? Does control voltage come from another transfo?

3. What are transient currents for each connection?

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Anonymous Poster #1
#19
In reply to #18

Re: Corrrect Delta Connection

12/01/2016 1:13 PM

I agree that different connection gives different transient peak every time, but in one type of connection the transient is always less than the other type. Here is a siemens paper explaining it. https://www.scribd.com/document/263348643/Star-Delta

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#22
In reply to #19

Re: Corrrect Delta Connection

12/02/2016 5:27 AM

That would answer #12⇑.

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#25
In reply to #19

Re: Corrrect Delta Connection

12/02/2016 1:05 PM

Cannot read referenced publication without taking subscription.....

But I guess the answer lies in the standard 3 leg, 3 phase transfo layout where the flux path is different for the outer legs, compared to middle leg.

Hence the leakage reactance is not the same for all 3 windings or interconnections.

This would show-up in the "one big motor per transfo" situation but not in the case, which folk are likely to assume, where motors are small relative to transfo. The questioner gave no sizes for motor or transfo

In "small" motor case, most of impedance would be in motor and transfo impedance variations would have small, insignificant, effect. Note that motor layout is symmetrical for all 3 phases, apart from manufacturing tolerance.

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#30
In reply to #25

Re: Corrrect Delta Connection

12/06/2016 5:42 AM

Thanks 67model,

Here is another link for the same siemens paper.

http://docplayer.net/21609301-Industrial-controls-sirius-controls.html

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#31
In reply to #30

Re: Corrrect Delta Connection

12/06/2016 8:55 AM

There is a very specific reference to the specific phase rotation associated with each connection, which you omitted.

While it appears that this document was translated to English, it is not such a bad job that the meaning is masked.

The bottom of Page 4 cites residual voltage in the stator, that has to be generated by residual magnetism in the rotor. This is a common enough phenomenon. It allows a motor to act as an induction generator, even if rotated with no excitation, with the right output circuit. As an example, that's why you get high voltage on your VFD dc bus when decelerating your motor with a high inertia load, the VFD supplies the excitation, the mechanical load supplies the energy to turn the rotor).

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#20
In reply to #18

Re: Corrrect Delta Connection

12/01/2016 1:51 PM

I would guess at rotor residual magnetism polarity working against you in one of the two cases, but you would need to establish or assume the phase rotation initially. I think only a closed transition starter would be able to consistently match up the timing among the 3 phases to always give an extra bump to one (or more) of the line currents...

Don't have the patience to proof this, tho...

(Siemens link blocked where I am...)

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#15

Re: Corrrect Delta Connection

12/01/2016 11:00 AM

Runs clockwise, counterclockwise or goes "POOF".

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#16
In reply to #15

Re: Corrrect Delta Connection

12/01/2016 11:02 AM

Correct answer: It hums because it doesn't know the words.

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#23
In reply to #16

Re: Corrrect Delta Connection

12/02/2016 5:28 AM

The old ones are the best.

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#21

Re: Correct Delta Connection

12/01/2016 6:05 PM

Once again, I am dumbfounded at how much time *I* have spent on THIS one, trying to read-and-re-read our (anonymous) poster's feeble attempts to define the REAL (and complete) question..... (not to mention filtering thru most of the replies).

Not until Post #12 do we learn that the "OP" question is to be taken "...in context of open transition star delta switching." And then, like "rwilliams", I cannot access the OP's link from post #19.

Jp_ more-or-less provides the "fundamental" response to: "If wrong connection is used, what will happen?"

But (IMHO) a more thorough response would be: In the case of being switched-TO this ("incorrect") Δ connection FROM a star ("soft-start") connection, result would most likely be plugging (aka, braking).

There are a plethora of descriptions on the web to help one understand the basics of 3ø rotating equipment (and, once again, here we are having to ASSUME a WHALE of a bunch of stuff that OUGHT-TO-HAVE-BEEN provided from the get-go... such as PW assuming that there IS protection installed!) BIG? small? Fast! slow? Heavily-loaded? Miniscule_load? OP could paint a "much-better-picture"!

The post GIVES the {'optional'} delta connections WITHOUT any reference whatsoever to the {supposed, as per post-12} initiating Star connection...Wye (?)

{pun intended}

Does ANYBODY SUPPOSE that maybe-perhaps the "result" (requested in the OP) just MIGHT-MEBBE depend a slight-smidgen on the configuration RELATIONSHIP (between the star-and-delta connections to "LINE")?

A Few Example Web Descriptions:

Wiki LearnEngineering.org & electrical-engineering-portal.com

If one is not going to "invest, study, and comprehend" (a task for which this forum {CR4} is an "easy-way-out"), then one should at LEAST put some real effort into the formation and delineation of their "problem" (or question).

<< shame on everyone who responded in knee-jerk fashion WITHOUT demanding more ... i.e., THOROUGH... information...!>>

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#24
In reply to #21

Re: Correct Delta Connection

12/02/2016 5:31 AM

<...shame on everyone who responded in knee-jerk fashion WITHOUT demanding more ... i.e., THOROUGH... information...>

It does behove original posters to supply thorough information at posting #1. Doing so saves readers an awful lot of time and avoids games of "20 Questions", to which this forum is historically averse.

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#26
In reply to #24

Re: Correct Delta Connection

12/02/2016 1:18 PM

"It does behoove original posters to supply thorough information at posting"...

Aye to that!

I have ranted about this issue a number of times in the past ... as I did at post# 17 here [(therein giving "GAs" to lyn for "1st responder" posts here, here and here)]...

and then, also at post# 8 here

and at post# 4 here

and at post# 21 (bottom-most) here.

And then , at this thread, although brich "acknowledged" my post# 15, not a single solitary person replied to it to ask me:

"To which manufacturers in Connecticut, California, and China are you referring?"

Ultimately, I was compelled to "rant" in post# 18, there, about the lack of sufficient info in CR4 "Questions".

There OUGTTA_BE a "lag-time" between SUBMITTING a "post", and having it actually posted.

This would give time for a "Moderator" to perform a "spell-check / grammar-check / sanity-check", and suggest-back to the (prospective) poster a few "Edits-for-consideration".

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#27
In reply to #26

Re: Correct Delta Connection

12/02/2016 5:33 PM

Yes! Sometimes, extracting the real question is like pulling teeth by telecontrol to Mars!

And in reply to original post, one could have said that both are "correct", but the two are 60 degrees apart (left might be Yd11 transfo, right Yd1), so paralleling could make one choice "flash-bang!" wrong.

Of course, the essential CR4 "crystal ball" saw that was not the real question.......

Perhaps, instead of engineering, there should be "palantiring" for communicating with "dark lords".

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#28
In reply to #27

Re: Correct Delta Connection

12/02/2016 7:11 PM

"Oy" ... THANK GOODNESS for Wiki:

((https://en.m.wikipedia.org/wiki/Palant%C3%ADr))

You are attempting to communicate-to a "senior citizen" who has never been able to watch an entire episode of Lord of the Rings, Harry Potter, or other such fantasy stuff....(!)

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#29
In reply to #28

Re: Correct Delta Connection

12/05/2016 7:51 AM

Before becoming a "senior citizen" myself, I bought & read the hardback books in 1966 & have read it since.

I apologise for it looking like a bit of "esoterrorism" [trying to impress people with esoteric references]. It seemed a word to sound good with engineering and crystal balls.

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#32
In reply to #26

Re: Correct Delta Connection

12/07/2016 7:18 AM

<...ranted...>

Rants are generally not good for blood pressure. The health and well-being of CR4 subscribers is always a top concern.

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#33
In reply to #32

Re: Correct Delta Connection

12/07/2016 8:42 AM

"Aye" that ... but still, "...time for a "Moderator" to perform a 'spell-check / grammar-check / sanity-check', and suggest-back to the (prospective) poster a few 'Edits-for-consideration'" would be a breath of fresh air, now-and-again...

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