Correct Delta Connection

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?

The drawing still cannot be read properly.

Is there a prize for getting it right?

Neither, as the drawing cannot be read properly.

Is there a prize for getting it right?

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

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

I agree...

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!!!

http://www.bing.com/images/search?q=delta+motor+wiring&view=detailv2&&id=E99C7A27526136C439CC26851A2166198A61FFB3&selectedIndex=0&ccid=q4vC3geG&simid=608001172313147012&thid=OIP.Mab8bc2de0786149f63b1e36b500aefadH0&ajaxhist=0

You need to work out the relationship between the three windings

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?

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

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?

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?

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

That would answer #12⇑.

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.

Thanks 67model,

Here is another link for the same siemens paper.

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

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).

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...)

Runs clockwise, counterclockwise or goes "POOF".

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

The old ones are the best.

<...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.

"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".

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".

<...ranted...>

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

"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...