Pa28 electrical system

[baobab72]

Hi
I am looking at the schematic of the electrical system for the pa28 and i am a bit puzzled: as far as i can tell, but correct me if i am wrong, the trckle charge to the electromagnet/rotor of the alternator is supplied from the MAIN dc bus through an ALT FIELD RELAY, an overvoltage relay and a VR.
The overvoltage relay will interrupt the trickle charge to the rotor causing the electromagnetic field to collapse and the alternator output to drop, should it sense an excessive current draw from the bus: is that correct? If so, would the alt field relay trip first? What is the difference - protection wise - between the field relay and the overvoltage relay?
The trickle charge from the field bus seems to be supplied through the master solenoid through a battery alternator interlock, how is that controlled? from the battery switch or from the alternator switch?
Also power from the alternator is fed into the master solenoid, what is its function?
Finally what is the alternator source power relay energizing circuit?

Many thanks

Baobab72

[AirborneAgain]

There are many different versions of the PA28, so you need to be more specific. (I'm looking at a PA28-181 (Archer II) POH right now and it doesn't have an alternator field relay.) Even better, scan the particular electrical system schematic you're looking at and link to it!

That said, generally speaking an overvoltage relay is just that -- a relay to turn off alternator output in case the alternator turns out too high a voltage. The current draw has nothing to do with it. Circuit breakers provide overcurrent protection.