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. It will never trip because the dynamo at 20 amp rating is incapable of supplying that current in the first place unless it goes into substantial overspeed. What should be included is over-voltage protection across the regulated output that breaks (or shunts) the circuit in the event of regulator failure. Breaking unregulated output by circuit breaker or simple switch generates huge voltages in the dynamo coils that could break down the insulation around the wires in it because the power from the coils spinning in the non-adjustable non turn offable magnetic field has nowhere else to go. You should never spin a dynamo without somewhere for the excess power to go.......even if it just literally a "crowbar" across the output. Alternators are very different because the coils are energised to produce the field (as opposed to magnet) and can thus be turned off. Spinning of the armature thus has no output and no adverse impact.
