# Y-∆ Starter



## ppsh (Jan 2, 2014)




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## varmit (Apr 19, 2009)

Seems to be a really bad idea to me, from a safety standpoint, to have power on a motor when it is not running. It looks like the classic " how cheap can we make this" mentality. I do not understand how this could be UL listed.

Most of the newer 50 HP and larger compressors, that I see, have a soft start or VFD. I recently checked on a replacement Wye- Delta starter. It would require a special order with a long lead time and I could by a VFD cheaper. Yes, I could assemble the components myself, but the VFD would still be less expensive.


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## CoolWill (Jan 5, 2019)

I occasionally do work in a plant with a bunch of 50 HP motors with this setup. I agree with your concerns, but in 10 years there I haven't seen it be a problem. I saw it on a 100 HP motor at a different place. Contacts welded and it sure let the smoke out, but the real problem was the contactors were undersized from the jump.


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## JRaef (Mar 23, 2009)

This is the standard scheme for elevator starters, has been for years. The first time I saw it I warned the OEM that this was fraught with dangers, they didn't care. They were after the cheapest possible working solution. 

But if you think about it, people who still use Y-D starters are already defining themselves as only being interested in cheap, because a solid state soft starter is WAY better and not that much more expensive (than a 3 contactor Y-D).


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## FarmerEngineer (Mar 18, 2021)

If you use a soft starter without an isolation contactor, you still have leakage current at the motor. In the right circumstances it’s enough to kill you.


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## wiz1997 (Mar 30, 2021)

Worked on some of these Quincy rotary compressors years ago.
We had a Quincy tech out one day doing a yearly check up.
I asked about there being power on the motor leads.
His reply was it keeps the motor warm and moisture out.
OK, it's their engineering.


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## micromind (Aug 11, 2007)

wiz1997 said:


> Worked on some of these Quincy rotary compressors years ago.
> We had a Quincy tech out one day doing a yearly check up.
> I asked about there being power on the motor leads.
> His reply was it keeps the motor warm and moisture out.
> OK, it's their engineering.


The tech doesn't know much about electricity.......in order for there to be heat, there needs to be current flow. There's no flow unless the motor is either starting or running.


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## 460 Delta (May 9, 2018)

micromind said:


> The tech doesn't know much about electricity.......in order for there to be heat, there needs to be current flow. There's no flow unless the motor is either starting or running.


Likely an answer that a factory engineer gave him an never questioned the logic of it.


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## paulengr (Oct 8, 2017)

FarmerEngineer said:


> If you use a soft starter without an isolation contactor, you still have leakage current at the motor. In the right circumstances it’s enough to kill you.


A standard test for SCR failure (shorted) is to him through the soft starter. In theory they can be down to 10k in the MV ones but in LV I’ve never seen much below 100k. So 480 / 100k is 4.8 mA, not enough to do more that tickle. If the SCR shorts the only protection is when the breaker/fuse trips. This is how 99% of soft starters are used at LV. At MV or with a 3 contactor bypass system they will have an output contactor. In a wye-delta with only two contactors one side of the motor is open because you have to connect all 6 leads (T1-T6) to do anything.

Maybe things have changed but 5 years ago at least Sullair, Gardner-Denver, Quincy, Atlas Crapco, and even currently Ingersol Rand use eye-delta starters almost exclusively as the default on all screw compressors. I don’t see it work on much below 50 HP.


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## macmikeman (Jan 23, 2007)

Upon loss of utility power situation, both of those contactors had better be fully open before utility power is restored. This would sorta seem obvious the coils open up on loss of power, but if any of those springs aren't working properly it is kaboom time.


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