Light twins electrical systems.

[TenaciousP]

Hello all

I'm trying to brush up on my DC electrics and have managed to totally confuse myself.

I would like to know the most common electrical system on light twins.

Are the alternators normally connected in parallel using load sharing circuits?

(I know that if this is the case then the line connector will not allow the alternator to connect to the busbar until the voltage is correct. I have flown quite a few different types and have never had to do this manually but I know it is also achieved automatically.)

OR

Is a split bus system more common.

Referring to my old ATPL notes, when talking about a split bus on a DC system, they are just referring to the separation of vital, essential and non-essential busbars. But in AC electrics they do refer to split busbars as a way of avoiding the necessity for load sharing circuits.

So in short, a Seneca for instance, parallel alternators or split bus?

Cheers.

[cessnarepairman]

Most light twins have voltage regulators which are connected together electrically, as one alternator starts to take more load than the other the regulator on the heavier loaded side ups the current to the lighter loaded side regulator & make it take a bit more of the load, hence balancing the load between the two.

That sort of system is definately used on Pipers like the Seneca & the Aztec. Balancing can be a nightmare if one or other Alternator has been changed, this tends to "upset" the system because the internal resistances of the old & the new alternators may be different. I had this once & the only way to get them balanced was to get another alternator from the same manufacturer for the other side.

Beechcraft tend to use a different system, althought they have 2 regulators one is a spare used only if he other goes U/S. The only way you can get the alternators to balance is to have completely equal resistance in the left & right system any high resistance connections will cause the other side to take more of the load.

[TenaciousP]

Very informative, thanks cessnarepairman.