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thermal overload relay current setting

thermal overload relay current setting

thermal overload relay current setting

(OP)
All,
Please explain to me the impact of the thermal overload relay current setting range.
I have a relay with the following current settings: 85%, 100%, 115%.
If at 100% setting, the relay trip at t100, what would be the trip time at 85% by just adjusting the current dial.
Likewise, what would be the trip time at 115% by just adjusting the current dial.
How can this be illustrated in the TCC?.

Thanks

Yigo

RE: thermal overload relay current setting

What that dial is setting is the pick-up point of the TCC, the shape of the curve stays the same.

So at 85%, if you have the heaters selected for for 100A, the trip curve starts at 85A, if you set the dial to 115%, the trip curve starts at 115A.

You cannot calculate the trip time without knowing the trip class.

"Will work for (the memory of) salami"

RE: thermal overload relay current setting

(OP)
Jraef,
To make sure I understand you, please let me state the issue in a different way.
I have TCC curves defined as time = f(I/I-trip).
During a test,the OL relay is set at 100%, the relay trips for a current named I-100.
Using TCC curves, the time is the point where TCC intersects the current line at
(I-100/I-trip).
During a second test, the OL relay is set at 85%, the relay trips for a current named I-85.
Using TCC curve to find the time, I want to know if the time is the point where TCC intersects the current
line at (I-85/I-trip), or (I-85 x 0.85/I-trip), or (I-85 / 0.85/I-trip),

Your comments are very appreciated

Thanks

Yigo

RE: thermal overload relay current setting

Set the overload to 100% and apply a current of X amps to the overload. It will trip in Y seconds. Now, set the overload to 85% and apply a current of 85% x X amps. It will again trip in Y seconds.

RE: thermal overload relay current setting

(OP)
Thank you for your responses.
You are all saying the same thing.
Moving the pick up 15% to the left or right would cause the curve
to shift to the left or right.
From my previous post, the right current is (I-85 x 0.85/I-trip).
Thanks again.

Yigo

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