Ouch... Where do I start.. Questions:
- How many power plants? ie Engines, APU, RAT, etc.
- Is you system going to be AC or DC based?
- What will be the prime voltage? 12, 24, or 48 volts
- Is there a ground power port? (makes life easy)
Well here is a overview of my airplane. You will notice that it is a twin. There are two alternators, and starters. You see my alternators have had the diodes ripped out of them so the unit produces AC at 400Hz which is accomplished by applying a 400Hz sine wave on the Alternator Exciter. By engaging the ALT1 or ALT2 contact or we can turn on the DC rectifier.
When the two alternators are out putting at same voltage and phase we can turn on the TIE RELAY so that each alternators can split the load. The AC TIE RELAY is used for isolation. That is if you have a alternator failure. The failed alternator can be isolated and its load can be support via the other alternator. (author CAH 17MAY2014)
There is also two other contactors one controls the EXTERNAL POWER the other is the battery disconnect.
In this way you can't discharge your battery via the EXTERNAL POWER JACK. The two Master Switches on the panel are a SPDT (Single Pole, Double Throw) with center off. So if both switches are in the EXTernal positions the 24vdc sense line is on only when the generator (external power) is on, which energizes the GROUND POWER RELAY, which in turn puts 24vdc on the BATTERY BUS.
So when you have the switches in GEN postilions, the alternator, is spinning happily, there is voltage on the BATTERY BUS from the DC rectifiers, controlling the battery when charging in flight or on the ramp.
Tune in later, more to come!
- What this diagram does not make clear is that both DC Rectifiers are attached to the Battery Charging Circuits via a diode so that you can not back feed the battery or the Chargers themselves.
- Also not shown is the DC BUSS TIE RELAY which ties both out puts together
- Also not shown is the BATTERY DC BUS TIE RELAY