DP contactor coil.

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ptonsparky

ptonsparky

Tom
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NE (9.06 miles @5.9 Degrees from Winged Horses)
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EC - retired
Yup, I think we will take the old coil back there today, 30 miles, take out the new one, reinstall the old, hook up the fluke 43b and the laptop cause that is the best I have, try it a few times, hopefully it doesn't smoke because we know what normaly would happen. Put the new coil back in if we can get the old separated from the armature, then repeat the process. And of course we will have donned the coveralls, face mask, gloves and hearing protection. Movie to follow.

I could ohm the 240v coil and compare with the 480 but after that some one else will have to do the math.
 
T

T.M.Haja Sahib

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George Stolz said:
Interesting. How do you measure the impedance of a coil?
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Impedance=voltage across the coil/Current through the coil.

If the impedances of the two coils are equal within the tolerance limits,the odd coli might be wrongly designated as 240V.........

If the impedance of the odd coil is very much higher than that of the new installed 480V coil,it means there was some internal fault in the coil and despite it,it was functioning.

If the impedance of the odd coil is very much lower than that of the new installed 480V coil,it is apparent that the OP is kidding......;)
 
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steve66

steve66

Senior Member
Location
Illinois
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Engineer
My only guess:

The control transformer probably didn't have enough capacity to fry the coil. As a result, the current through the coil probably dropped the transfromer voltage enough that the coil didn't fry, and the transformer probably didn't die either.

That means it may have been a very lucky balance - a transformer with a higher VA capacity probably would have fried the coil, one with a lower VA capacity, and the control transformer probably would have fried.


Steve
 
T

T.M.Haja Sahib

Guest
steve66 said:
My only guess:

The control transformer probably didn't have enough capacity to fry the coil. As a result, the current through the coil probably dropped the transfromer voltage enough that the coil didn't fry, and the transformer probably didn't die either.

That means it may have been a very lucky balance - a transformer with a higher VA capacity probably would have fried the coil, one with a lower VA capacity, and the control transformer probably would have fried.


Steve
Click to expand...

In that case the contactor would have dropped out due to low coil voltage much lower than 240V........
 
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steve66

steve66

Senior Member
Location
Illinois
Occupation
Engineer
T.M.Haja Sahib said:
In that case the contactor would have dropped out due to low coil voltage much lower than 240V........
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I didn't say it dropped that low. I was thinking the 480V contol voltage dropped somewhere closer to the 240-300 volt range. Just enough that it didn't fry the coil.

ptonsparky said:
No control transformer.
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But that blows that theory.

K8MHZ said:
How easy is it to remove the coil from the contactor? It may have been swapped to expedite a repair at some time in the past.
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I think that's a very possible explaination.

Did you actually measure the voltage across the old coil?

By the way, I had a lighting rep come in yesterday, and he plugged his 12V LED lights into his 24V power supply. I can guarentee he didn't have the same luck this coil seems to have had :)
 
ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
steve66 said:
I didn't say it dropped that low. I was thinking the 480V contol voltage dropped somewhere closer to the 240-300 volt range. Just enough that it didn't fry the coil.



But that blows that theory.



I think that's a very possible explaination.

Did you actually measure the voltage across the old coil?

By the way, I had a lighting rep come in yesterday, and he plugged his 12V LED lights into his 24V power supply. I can guarentee he didn't have the same luck this coil seems to have had :)
Click to expand...

No. We had no reason to. It worked before the fire. Conduit was cutoff when we removed the smoke and water damaged distribution panel. My help discovered the coil voltage dilemma when they were removing old wires. The label is obvious from the line terminals if you have good eyes and are close enough. I had megged the starter, line & load side along with the pressure switch the day before. This would have found a bootlegged bond to the EG for 277 operation. My help physically looked for that connection because that was his first thought after "WTH?"
 
T

T.M.Haja Sahib

Guest
Congratulations!You have found a super coil able to withstand 480V above its rated 240V.
Or,does the coil of that particular make rated 240V is able to withstand up to 480V?May be checked up with the manufacturer.
 
ActionDave

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
Well, if they could make one coil that could be used on multiple voltages why would they make two?

On second thought maybe they do and they are just charging more for the one labelled with the higher voltage. I might start testing all my coils with the highest voltage available.
 
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