the final generator/alternator related question

[baobab72]

Dear All

i have a couple of final questions about the generator/alternator used on trainers which might help to dissipate my doubts once for all, since i guess i had it wrong cos i was under the impresson that the trickle charge from the battery to the VR was fed to the stator and that the rotating armature was actually the component supplying the emf! while if i understand it correctly, the stator consisting of the 3 coils spaced 120° apart and built around the rotor driven by the engine is the one supplying the AC! emf which is induced as the trickle charge is supplied to the rotating armature aka field coil, through the slip rings/brush assembly, generating an electromagnetic field and in which the same armature is spun – Faraday’s principle stating that whenver a conductor is moved into an electromagnetic field a certain emf is induced in the conductor – in this case the source of the electromagnetic field is represented by the rotor while the conductor by the stator! – and the magnitude of the emf is proportional to the relative velocty of the conductor with respect to the electromagnetic field and to the strength of the same field!
Is that a correct statement?
also what is the function of the BATT switch, the ALT switch i guess controls the trickle charge to the VR and then to the rotor through an alternator field relay – in case of an overvoltage the VR will trip the relay, cutting off the trickle charge to the field coil, causing the electromagnetic field to collapse and thus the output of the alternator to drop to zero! but the BATT switch what does it exactly control?
Also how is the emf picked from the stator?
And finally the right sequence for the CB’s is SOURCE –> CB –> switch –> item or source –> switch –> CB –> item?

many thanks!!
Baobab72

[glad rag]

Q. So what happens when the battery goes flat?

[EEngr]

Dear All

i have a couple of final questions about the generator/alternator used on trainers which might help to dissipate my doubts once for all, .....

while if i understand it correctly, the stator consisting of the 3 coils spaced 120° apart and built around the rotor driven by the engine is the one supplying the AC! emf which is induced as the trickle charge is supplied to the rotating armature aka field coil, through the slip rings/brush assembly, generating an electromagnetic field and in which the same armature is spun ....

Is that a correct statement?

That's pretty good. We usually refer to the "trickle charge" as field current. The magnetic field produced is proportional to this field current and the resulting stator emf is proportional to the product of this and the velocity at which it crosses the stator windings.

The "alternator, generator" nomenclature is often used interchangeably. Old style DC generators had low current fields on their stators and took high current power off their rotor via a brush type commutator. But high current brushes are a maintenance nightmare. So the rotating field, fixed stator design was adopted from utility type AC generators once suitable solid state rectifiers became available. The name "alternator" distinguishes this design from the former brush commutated "generator" used for automotive and aircraft DC systems in the old days. On larger aircraft, the generator is still referred to as a generator, differing from an alternator only in that it directly supplies AC buses and loads (and by its capacity).

The other stuff about BAT and ALT switches I'll leave to the folks familiar with trainers and similar aircraft. These have different functions that those on the "big jets" I'm more familiar with.