Thermal Overload Relay Testing 1

[mellomain]

I am testing Cutler Hammer C306 bi-metallic TOLs. Should the poles be tested individually or in series?

Man is troubled by what might be called the Dog Wish, a strange and involved compulsion to be as happy and carefree as a dog --- James Thurber

 

[waross]

It depends.
What are you testing for?
Note that the size of the conductors may affect the calibration. Conductors should be sized based on 75 deg. insulation.
If you test individually the relay should trip early due to differential action. If you test in series you may not identify a late tripping pole.
A complete test would include testing with rated current through two poles and a variable current through the pole under test as well as a test with the same current through all three poles in series. This way you will be able to test both differential action and overload tripping.
However, if you have a nuisance tripping issues, a first, fast test would be all three poles in series at rated current.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mellomain]

I am conducting periodic testing (5 year frequency) to verify that the relay will trip within the time specified on its characteristic curve. I test at 300% of the current setting for example. The curve does not state whether or not it was developed for a single pole.

Man is troubled by what might be called the Dog Wish, a strange and involved compulsion to be as happy and carefree as a dog --- James Thurber

 

[waross]

Test with three poles in series. Doing this test on individual poles will probably result in cross issues with the differential action.
Use the same size conductors for the test connections as are used in service. The conductor acts as a heat sink and a different size conductor may bias the results. Probably not much at 300% but using the same size wire removes all doubt.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

Out of curiosity, what do you believe is the pass-fail point at 300%?


"Will work for salami"

 

[mellomain]

24 to 209 seconds from my Freedom C306 Class 20 trip curve.

Man is troubled by what might be called the Dog Wish, a strange and involved compulsion to be as happy and carefree as a dog --- James Thurber

 

[mellomain]

jraef,
what I meant was that 24 to 209 is acceptable. Anything outside of that is unacceptable and requires further investigation. Could be a test method problem or could be a component issue.

Man is troubled by what might be called the Dog Wish, a strange and involved compulsion to be as happy and carefree as a dog --- James Thurber

 

[jraef]

No. what I was getting at, just making sure you understood that the range is that wide.


"Will work for salami"