Hi folks Yes, I agree with Paul, the function is too protect the wiring but, in the permanent magnet dynamo (20amp) setup, the only component capable of supplying 35amps or more throughout the system wiring is the battery thus the circuit breaker should be immediately downstream of the battery (not in the dynamo output where it can never trip thereby providing no insurance). You can't get blood out of a stone.
Different story with a normal alternator (or a bigger dynamo) that is capable of supplying 35 amps or more. By all means protect your wiring with a breaker as per your usual arrangement in aircraft. A dynamo regulator failure allowing excess unrectified AC or DC voltage (depending on the failure) to pass into the system is dealt with using an overvoltage circuit that should drive a relay in the dynamo outputs to isolate the dynamo. Excess voltage will not trip a circuit breaker that relies on current for its function. It is the load on the circuit from your equipment (as normal or in failure) that will determine the current flow through the wiring but only up to the maximum that the dynamo can produce (20 amp rating). Anything more comes out of the battery (anything up to welding current)!!!. Your KR must be getting really close now up there in Brissie....go the cowboys :-) Regards John. John Martindale 29 Jane Circuit Toormina NSW 2452 Australia ph:61 2 6658 4767 m:0403 432179 email:john_martindale at bigpond.com web site: -----Original Message----- From: KRnet [mailto:krnet-bounces at list.krnet.org] On Behalf Of Paul & Karen Smith via KRnet Sent: Saturday, 3 October 2015 6:40 AM To: 'KRnet' Cc: Paul & Karen Smith Subject: Re: KR> Electrical System Hi all, Circuit breakers and fuses are installed into systems solely to protect the wiring form too high current that could cause a fire. Selecting the amp rating of a breaker is a function of the maximum current carrying capacity of the conductor/insulation pair based on whether it is in free air or inside a mass bundle. Using one as the trigger for overvoltage protection might damage the generator but it will save the many thousands of dollars of other electronic systems in your plane. Good insurance I'd say. Paul. -----Original Message----- Cc: John Martindale Subject: Re: KR> Electrical System Hmmm, in which case having a 35amp circuit breaker in its unregulated output is pointless. ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2015.0.6140 / Virus Database: 4435/10744 - Release Date: 10/02/15
