DA42 Electrical Generation Question?
 

Hi guys,

Hope your well.

I have been reading about the electric systems for the DA42, and would just require some clarification on some parts written in the AFM:

If I can quote the following:

7.10.1 GENERAL
The DA 42 has 28 Volt DC system, which can be sub-divided into:
- Power generation
- Storage
- Distribution
- Consumers
Power generation
Power generation is provided by two 60 ampère alternators (generators) which are mounted on the bottom left side of each engine. The alternators are driven by a flat-belt.
The power output line of the left-hand alternator is connected to the 'LH main bus' via

Now it says that is has a DC system, and says that the power gen is from altenrators (gens). However going back to my basic understanding of electrics, do alternators not only produce AC ? So where does the DC come from?

Also, the aircraft has an "alternator control unit" to ensure constant power - which might suppose that it is AC, but obviously not.

So, could I ask what is going on here? Is it AC converted to DC? Or the alternators produced DC straight as well? Or is ot the wording I am not seeing?

Thanks alot guys
GWA

Alternators will produce alternating current, which is converted to direct current by a diode pack "rectifier" which is inside the alternator. Thus, what you get out of an alternator will be DC electricity.

The alternator control unit is probably a "Voltage regulator", which senses the system voltage, and controls the alternator field power so as to control the output of the alternator to produce the required voltage. This is why most aircraft with alternators have over voltage protection systems, so if the voltage regulator quits, the alternators are taken offline, before they provide enough voltage to damage things.