LTD you're right, it's the Time-Current Curve. It illustrates how long before a circuit breaker will trip at a given current.
Originally Posted by noah katz
Not all breakers are the same.
I agree, you're right,...they're not all the same
|Just the ticket for us, though I don't know if they're available as direct replacements for standard home breakers
A standard breaker you buy at your local hardware store will suffice. They're designed as to not nuisance trip, when dealing with huge currents encountered with motor start up. Items like an A/C condensing unit starting up, or a refrigerator compressor etc. Motors, at start up, pull enormous currents to transition from stationary to full speed. The circuit mimics a near short circuit for an instant, thus pulling several times it normal amount of current until the speed ramps up. This is why one may see the lights dim briefly coinciding with these events.
These effects aren't subtle, as I can attest. I've heard it countless times. Being in an electrical gear room, with the constant hum and buzz of big dry type transformers. Then, accompanying the start up of a motor elsewhere in the facility, one of the hundreds of conduits in the room buzz's and vibrates loudly as the circuit feeding the starting motor draws so much current, that the wires magnetic field interact violently inside the conduit. They alternately repel one another etc, buzzing momentarily until the motor builds up speed and the current normalizes.
That's ideal anecdotal evidence of the Time Current Curve of the breaker allowing 100 amps or more to flow in a 20 amp circuit.
btw, found a different trip curve; here