Mailing List lml@lancaironline.net Message #63214
From: Brent Regan <brent@regandesigns.com>
Sender: <marv@lancaironline.net>
Subject: Re: TCM 60A alternator--diodes
Date: Mon, 22 Oct 2012 10:12:23 -0400
To: <lml@lancaironline.net>
Wolfgang, Paul and Gary are three smart guys having trouble wrapping their heads around 3-phase circuits. Tesla, also a smart guy, went insane doing the same thing.

The best way to look at it is from the DC side and not the 3-phase AC "crazy" side.

Think of it this way. Current flows in a circuit and the diodes are the gatekeepers to the alternator windings. Current flows out of one end of the alternator stator winding, through a diode, through the aircraft and then through another diode to the other end of the winding. Circuit complete. Current is another way of of saying electron flow. In plumbing, flow can be measured in gallons per hour. The alternator has three phases, or circuits, in parallel. In plumbing it would be three pipes. Imagine you have to fill a tank at the rate of 100 gallons per hour. If you had three equal pipes flowing into the tank each pipe would need to flow 33-1/3 gallons per hour. Likewise to get an average current of 100 amps from three equal parallel sources, each source would need to deliver 33-1/3 amps worth of electrons.

The relationship between phase voltage and line voltage and phase current and line current depend on if the alternator is wired as a Wye or a Delta so that whole square root of 3 term may or may not apply.

We do know that for Wye and Delta the average power in each of the wires is 1/3 of the total power produced. Since the voltage drop across a diode is fixed (~0.6V) and power is the product of voltage and current then the current must also be 1/3 of the total current.

Regards

Brent Regan
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