Half a minute? I missed that.This is what is interesting then Jraef.
We've a scenario where an OCPD can spike up to 6O odd amps for what i'm reading is up to 1/2 minute ,it's apparently not going to bother with the handle current for this amount of time ,instead buzzing it's discontent....
Methinks most of us have been privy to this phenomenon here...
What is happening to this circuit during this event? What is the OCPD 'seeing' or not seeing ?
I know I am not telling Jraef anything here just adding that each fuse does as well. It would be very difficult to start a motor or transformer if OCPDs instantly tripped at their marked rating.EVERY breaker has a trip curve.
More , what problem should we be focused on Mr Iwire...What problem are we trying to fix?
More the reason for what electrical fires did occur...Are we trying to find a way to prevent the huge numbers of electrical fires used to prove the need for AFCIs that never really happened?
You make my point sir, thxKeep in mind, regardless of Peters on site observations the circuit breaker did function and prevented a fire. The homeowner had reset it a number of times before calling in an electrician.
Well, this guy is:What problem are we trying to fix?
Are we trying to find a way to prevent the huge numbers of electrical fires used to prove the need for AFCIs that never really happened?
Of course thats my point. Despite not tripping magnetically (and what better example then FPE which has no magnetic trip) no fire resulted unlike what the industry otherwise claims. This is key here.Keep in mind, regardless of Peters on site observations the circuit breaker did function and prevented a fire. The homeowner had reset it a number of times before calling in an electrician.
rj,That an OCPD is designed to absorb a spike is a given we all accept.
The duration of the spike is what is intriguing here....
Disposals assume nuisance trips from lower settings , yet ground faults of just the right impedance may hum the flight of the bumblebee.
I think most here have been witness to this , in fact i've even had customers place their phones near panels ,resetting their 'vocal breakers' for my listening pleasure
This is not a short duration event, not 2,3,5,7 seconds, doesn't quite seem proprietary to any one make/model either. One would think enough magnetic flux builds up for the handle rating to mitigate it within this time ?
Having been under the impression the thermal qualities were slow , the mag trip fast ,is apparently not quite right then?
So i'm imagining all those circuits, components ,devices, lamp cords ,wire nuts , egc's, etc designed for 15 amps suffering the ill effects of this.....?
Some of this is starting to sink in....>
modified mag trip
Obviously, the solution is to duct tape the breaker handle in the ON position so that it won't trip any more. I am surprised that none of you bright boys came up with it.I did not leave the breaker on long enough to find out. Generally speaking, when you hear a loud abnormal hum, that's a good sign that something is wrong and you should shut the breaker off. Before we arrived, the homeowner would reset it and it would stay on for some time, much longer than 25 seconds in its faulted condition.
Can you explain this further? Are you saying only 1 half cycle of current can unlatch the mechanism? :dunce:rj,
What you are missing is that "magnetic flux" does not build up over time. It reaches a maximum once in each half cycle and goes back through zero again.
The magnetic force has to be large enough to overcome spring resistance and then the trip will happen, just like a snap switch going over center.
For practical purposes (not considering mechanical inertia) there is no time element involved in the trip other than the length of time if takes the contacts to open once the trip is committed.
P.S. I usually consider a spike to be a reference to a sub-cycle event rather than a motor starting surge.
Of sufficient magnitude, yes, that's why it is referred to as an "instantaneous trip".Can you explain this further? Are you saying only 1 half cycle of current can unlatch the mechanism? :dunce:
Yes, for the magnetic trip.Can you explain this further? Are you saying only 1 half cycle of current can unlatch the mechanism? :dunce:
So I only need a half cycle spike to open the breaker? Must this spike be sinusoidal?Yes, for the magnetic trip.
I can "trip" a snap switch by pushing steadily harder and harder until it finally actuates, or I can apply a slightly larger force suddenly by bouncing something off the switch handle.
There is a certain amount of motion required to move the handle of a snap switch from the rest position to the tripped position. The internal mechanism of a mag breaker is designed to minimize the corresponding distance.
Jraef explains it in much more detail.
Hooboy, is there gonna be a test on this? JR?Of sufficient magnitude, yes, that's why it is referred to as an "instantaneous trip".
The current doesn't have to physically force the power contacts open, that's done with spring force. All the trip unit does is move a pawl on a catch that is holding the mechanism closed against the spring force. It doesn't need to move much to release it, just a fraction of an inch. The way the inexpensive resi breakers work is that there is a horseshoe shaped current path that all current needs to take. High current flow causes magnetic fields in those components to repel each other (look up "Ampère's force law" to understand this). If the current rises slowly, the components can absorb the mechanical force and spread it out so that it doesn't trip, giving the thermal element time to react. But a fast rise of that current makes it so that the mechanical force increases rapidly with no time for dissipation and it moves the pawl off the catch. From that point on, it's just the time it takes for the contacts to separate enough for the dielectric needed for the available voltage to stop current from flowing as the arc is quenched.