ptonsparky
Tom
- Occupation
- EC - retired
Anybody have their handy dandy SQ D catalog close by? I need the resistance of a 8536SE01SY59 coil. 120V coil for a size 3 starter.
SQ D coil resistance
- Thread starter ptonsparky
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kwired
Electron manager
- Location
- NE Nebraska
Do they have resistance published someplace? I'm not finding it. I even did google search for cat number you gave and all that turned up is this thread on this site.
jdcpe17
Member
- Location
- Austin, Texas
wow... google is fast...
ptonsparky
Tom
- Occupation
- EC - retired
Not sure if they do. Help was at a dairy with starter that would not pull in. Hummed. He had already replaced the control transformer. I suspect replacement was to small.
Or coil shorted. He had about 8 ohms.
Or coil shorted. He had about 8 ohms.
kwired
Electron manager
- Location
- NE Nebraska
Transformer may have been too small for pull in but if you physically push it in it probably would be large enough to hold it in. Would give you idea right then that the coil was good.
Don't ask me how to physically push it in and comply with 70E though.
My experience if you have continuity and no melted plastic in the case they are usually good.
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ptonsparky
Tom
- Occupation
- EC - retired
Yea, safety was a consideration, and even if it did hold in, no one would have been around to push it on next go around. I was to far away and just did not want to suggest it. Well, I did want to, just didn't.
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
If it was humming and he had 120v on the coil terminals, I'd say the coil is bad. If the control transformer was bad or weak, I wouldn't think he'd have a full 120v on the coil terminals while it was trying to pull in.
ptonsparky
Tom
- Occupation
- EC - retired
In my opinion the best thing to do is to get the VA for that coil which should be published and assure that your CPT is large enough to provide the VA that is required. It is not often that a manufacturer publishes coil resistance as that value often time is not relevant. If you were to have two starters with the same coils you may try comparing their resistance which may provide some direction.
But first go to the Square D catalog which should have the power requirements listed for the coils of their starters.
But first go to the Square D catalog which should have the power requirements listed for the coils of their starters.
kwired
Electron manager
- Location
- NE Nebraska
The thing with the coil is it takes more VA to pull it in than it takes to hold it in.
According to Square D catalog a size 3, 3 pole contactor coil like in the OP requires 678 in-rush VA, and 47 sealed VA.
A transformer would not have to be 678 VA to run this coil, it would just need to be able to deliver that for a short time to pull it in and then only need to provide 47 VA continuously after that.
You are correct Kwired.
But it does no good to use a CPT that doesn't have enough VA to even pull in the coil. CPTs are designed diffent than the common transformer in that they do not have an even turns ratio. The becomes evident when you attempt to use one as a step up transformer and find that the HV side puts out a lower voltage than is anticipated. CPTs are designed to help reduce voltage drop while providing inrush current. In other words a 480-120 CPT is not actually a 4:1 ratio but the secondary is slightly higher than 1 which translates to a slightly higher secondary voltage than 120v.
But you still must size the CPT so that it is capable of supplying inrush current even though it is not sized to provide the inrush KVA continually.
When trying to draw too much inrush current from a CPT that is sized too small you will end up with the voltage taking a big nose dive at that time.
But it does no good to use a CPT that doesn't have enough VA to even pull in the coil. CPTs are designed diffent than the common transformer in that they do not have an even turns ratio. The becomes evident when you attempt to use one as a step up transformer and find that the HV side puts out a lower voltage than is anticipated. CPTs are designed to help reduce voltage drop while providing inrush current. In other words a 480-120 CPT is not actually a 4:1 ratio but the secondary is slightly higher than 1 which translates to a slightly higher secondary voltage than 120v.
But you still must size the CPT so that it is capable of supplying inrush current even though it is not sized to provide the inrush KVA continually.
When trying to draw too much inrush current from a CPT that is sized too small you will end up with the voltage taking a big nose dive at that time.
ptonsparky
Tom
- Occupation
- EC - retired
According to the partial Sola pdf I can access via Google and the info Kwired provided, I need a control transformer capable of 725 va. Good, now if I could just see the rest of that PDF...
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
That alone tells me it's too small, if the coil was shorted it'd wipe out the transformer secondary fuse.
FactoryMation has a neat little table in their catalogs transformer section for sizing control transformers. Using the info Kwired provided, it looks like a 150VA transformer is about right. 100VA seems borderline.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
If you had ordered a size 3 starter with transformer from Square D, they would have used a 150VA machine tool transformer, their number 9070T150D1.
kwired
Electron manager
- Location
- NE Nebraska
That is a big transformer for one coil, it is a somewhat large coil but still doesn't require much power other than at inrush. I think the 150 VA that others have suggested is probably what was needed.
I agree with that and I think your point:
is pretty much spot on.
A couple of other points/thoughts.
You can usually tell a burnt out coil by the acrid smell. Once experienced, never forgotten.
If the control panel transformer isn't man enough for the job and the contactor sits there with the coil energised, even at reduced voltage, but not pulled in that will give both the coil and the transformer a very hard time. If it persists for any significant duration, I would expect both to fail. And it to be very obvious that they had.
Just my two cents worth. Or two pence worth...
ptonsparky
Tom
- Occupation
- EC - retired
Details, details, details
Details, details, details
The transformer we, my help, took out was a ...100D1. IDK if the inrush capabilities are comparable with that of a SOLA 100va, but the Sola would be about 70% of what their sizing rules would suggest. The 50va we had on hand about 30%. We are taking up a 150.
The existing 100 had a 10amp fuse on the secondary side. Maybe why the primary side windings went TU. You suppose.
The secondary fuse on the 50 should have blown but, :rant: and there will be a disussion on this, he just used the 10 amp from the original CT.
SQ D just notified me the ohm reading should be in the "single digits" for that coil.
Thank you.
The 8536... # was the starter, not the coil. My mistake. He gave me both.
Details, details, details
The transformer we, my help, took out was a ...100D1. IDK if the inrush capabilities are comparable with that of a SOLA 100va, but the Sola would be about 70% of what their sizing rules would suggest. The 50va we had on hand about 30%. We are taking up a 150.
The existing 100 had a 10amp fuse on the secondary side. Maybe why the primary side windings went TU. You suppose.
The secondary fuse on the 50 should have blown but, :rant: and there will be a disussion on this, he just used the 10 amp from the original CT.
SQ D just notified me the ohm reading should be in the "single digits" for that coil.
Thank you.
The 8536... # was the starter, not the coil. My mistake. He gave me both.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
For the most part the characteristics are similar between manufacturers for similar products. A machine tool transformer is designed to provide about 6x inrush, whereas a normal power transformer is only about 4x and a 'furnace transformer' maybe only 3-4x.
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