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Circuit Breakers and electrical failure

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Circuit Breakers and electrical failure

Postby benih » Sun Mar 18, 2018 11:32 am

Hello,
i'm currently implementing failures in the c182s project and wonder how the behavior with electrical failure should be.

In the event of failure of an electrical component, does the associated breaker usually trip?
I would assume this since this most often would indicate electrical malfunction resulting in a short circuit?

Currently i think of a random chance that when failure occurs, the breaker will trip.
This yields three outcomes when failure occurs:
1. Just the breaker trips -> reset and all is fine (just some temporary malfunction or overvoltage?)
2. Just the equipment fails -> its dead but he remaining components on the elec circuit remain working
3. Both, breaker trips and equipment dead -> reset breaker to bring back the oher bus equipment

I think that 1. should probably be the rarest case and 3. the most common, how is this in the real world?
Also probably there should be cases where reenabling the breaker should immediately trip the breaker again (elec short sitation)?
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Re: Circuit Breakers and electrical failure

Postby Thorsten » Sun Mar 18, 2018 11:50 am

From experience with household appliances, I'd assume that only a minority of electrical failures causes a short. Usually things are just 'dead'.

If you get a short caused by an actual failure (rather than microwave, water boiler, toaster and vacuum cleaner all on the same plug...), resetting the breaker never helps, the faulty equipment needs to be disconnected.

It then depends on how your electrical system works. If the breaker actually isolates a circuit, you can use the rest of the bus normally if the breaker is out. If the breaker protects the bus itself, the bus remains dead.

(Not sure how much this helps, but procedures for an electrical failure aboard the Shuttle is to isolate the bad bus and not use it at all and rather to use the remaining good buses).
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Re: Circuit Breakers and electrical failure

Postby Alant » Sun Mar 18, 2018 1:16 pm

Do you have a crew manual that gives the actions to be taken following an electrical malfunction?

Alan
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Re: Circuit Breakers and electrical failure

Postby benih » Sun Mar 18, 2018 8:41 pm

The POH mentions something, i think.
But my question was meant more in the general direction...
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Re: Circuit Breakers and electrical failure

Postby Alant » Sun Mar 18, 2018 9:54 pm

I would suggest that you read section 7 of the POH, and simulate electrical failures, their effects, and the recovery actions to be taken exactly as described. Just doing this work will keep you occupied for some time, and is a good start point.

In general circuit breakers do not usually pop out of their own accord. Either there is a short circuit or other overload in the circuit that they are protecting, or the pilot has pulled it deliberately.

Having said that it is not unknown for voltage spikes to cause random failures, but you will need to research this yourself. In our house nearby lightning storms cause random circuit breakers to trip, both inside the house and in the electrical supply company´s network. In an aircraft such a storm may also damage communications and avionics equipment. It is up to you how deep you want to get into this subject. If you are VFR then you should not be in such as storm.

Alan
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Re: Circuit Breakers and electrical failure

Postby benih » Mon Mar 19, 2018 8:35 am

Thanks! That was helpful!
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