wye-delta wires slapping

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Educate me here.... Is it possible that the magnetic field built up in one state is collapsing and when the other state is closed the field then conflicts with the incoming current. Maybe not so much of an inrush but and outrush... I remember as a kid I played with a 12 volt relay transformer. Every time I removed the power leads I would get shocked. I soon learned and realized that this was the field collapsing in and causing a significantly higher voltage then what was put in.
 
jim dungar said:
An open-transition starter never closes both wye and delta contactors at the same time, it would create a short circuit. A closed-transition starter has a third contactor and a set of resistors.

But, reading my previous post, I can see how you might have thought I was saying that closed transition wye-delta starting was not available as an option.
Click to expand...

re: 1st P ? Nothing I didn't already know... but I thought the application guide might help others better understand the options and how they work in not-overly-technical jargon.

re: 2nd P ? Yes, that is how I took it the first time I read it... but upon reading the second time I noticed the emphasis on "closed" and realized you meant out of the normal context... yet I also thought others may not come to the same realization. Providing the link to the guide was just an easy way of covering all my thoughts in someone elses already written words (w/pictures and other graphical aids, too! :grin:)
 
mikeames said:
Educate me here.... Is it possible that the magnetic field built up in one state is collapsing and when the other state is closed the field then conflicts with the incoming current. Maybe not so much of an inrush but and outrush... I remember as a kid I played with a 12 volt relay transformer. Every time I removed the power leads I would get shocked. I soon learned and realized that this was the field collapsing in and causing a significantly higher voltage then what was put in.
Click to expand...

The "short" of it is that during the disconnected transition interval, the motor becomes a static generator (i.e. not connected but the magnetic fields are still pushing, pulling charges to the ends of the windings). The phasing will begin aligned to the wye connected state then shift a little as momentum is decreased mechanically. Now add to this that fact that delta phasing is + or ? 30? out of phase with wye. When the delta connection is made, the "generator" either bucks or boosts the current, depending on how the connections are made.
 
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