Motor Circuit Breakers

Status
Not open for further replies.
paulengr said:
No but even the GE that appears “thermal mag” is electronic (microprocessor). In breakers the least reliable are analog electronics like the old SqD SE’s. Next most reliable are thermal mags. Most reliable are microprocessor trip units.
Click to expand...

And the most reliable are fuses 😃😁

Question- how well do micros tolerate over voltage?
 
mbrooke said:
And the most reliable are fuses

Question- how well do micros tolerate over voltage?
Click to expand...

That depends...Advantage starters not so well! Those are discontinued for a reason.

The typical switchgear arrangement is to use an external DC source (typically 125 VDC). For self contained systems the power supply is the CTs. Most don’t “wake up” below 10-25% load. You can also use an external or internal battery. This is needed for programming. I have not seen one that does not work if the battery is dead...it just doesn’t show a display until the current wakes it up.

That is why there must always be some kind of non-microprocessor high current limit no matter what. Since all magnetics saturate this is a built in current (voltage) limit. Usually it’s around 20x the CT rating so above that point it clips. There is software compensation for clipping on the measurements so don’t think this is a limitation.
 
paulengr said:
That depends...Advantage starters not so well! Those are discontinued for a reason.

The typical switchgear arrangement is to use an external DC source (typically 125 VDC). For self contained systems the power supply is the CTs. Most don’t “wake up” below 10-25% load. You can also use an external or internal battery. This is needed for programming. I have not seen one that does not work if the battery is dead...it just doesn’t show a display until the current wakes it up.

That is why there must always be some kind of non-microprocessor high current limit no matter what. Since all magnetics saturate this is a built in current (voltage) limit. Usually it’s around 20x the CT rating so above that point it clips. There is software compensation for clipping on the measurements so don’t think this is a limitation.
Click to expand...


How long does it take for a breaker to "wake up" if the bat is dead? I'm thinking 10% load to short circuit. Where does the trip solenoid gets its power from?
 
paulengr said:
That depends...Advantage starters not so well! Those are discontinued for a reason.

The typical switchgear arrangement is to use an external DC source (typically 125 VDC). For self contained systems the power supply is the CTs. Most don’t “wake up” below 10-25% load. You can also use an external or internal battery. This is needed for programming. I have not seen one that does not work if the battery is dead...it just doesn’t show a display until the current wakes it up.

That is why there must always be some kind of non-microprocessor high current limit no matter what. Since all magnetics saturate this is a built in current (voltage) limit. Usually it’s around 20x the CT rating so above that point it clips. There is software compensation for clipping on the measurements so don’t think this is a limitation.
Click to expand...


Any idea of the largest size thermal mag breaker offered by GE or CH? It seems like electronics are taking over.
 
mbrooke said:
How long does it take for a breaker to "wake up" if the bat is dead? I'm thinking 10% load to short circuit. Where does the trip solenoid gets its power from?
Click to expand...

It has to boot up. Milliseconds of time. That’s GE micro versatrips. But Square D just needs 150 V+ power between phases but somehow limits maximum voltage (transformers? Diodes?)

Trip solenoid is same thing.

When testing there are always special procedures since during a primary injection test you use a few volts of power at full trip current (kA). Depending on the trip unit you have to say rig up test power through the battery connection while running the test or put power through certain phases.
 
Status
Not open for further replies.
Top