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howado
Joined: 23 Aug 2006
Posts: 7
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 Posted: Wed Jul 25, 2007 3:23 pm Post subject: Jabiru 3300 PMA |
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Thanks to the responders to my questions about the Jabiru alternator circuitry, esp to Craig Payne.
The Z-20 diagram shows the output from the regulator connected to a capacitor. Jabiru does not supply this cap with the engine. The West Coast Jab dealer has, however, put one in his Jab demo aircraft.
When you disconnect the alternator from the load the pulse signals from the stator winding drop to a low value, causing the tachometer to drop to zero.
The Z-20 diagram shows the red and yellow wires tied together, but the Jabiru schematic separates them, putting the red wire on the bus and the yellow wire on the battery plus terminal. They are separated electrically by a few milliohms, so tying them together probably works.
The Jab schematic shows the red wire coming from the regulator pin 5 while Z-20 shows the red wire coming from pin 6. Looks like the red and yellow wires are mixed up. I will try to get Jab to sort this out.
Howard Carter
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craig(at)craigandjean.com
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| Posted: Wed Jul 25, 2007 4:15 pm Post subject: Jabiru 3300 PMA |
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The Jabiru 3300 Instruction & Maintenance manual shows the internal
schematic of the voltage regulator. In the March 2006 version it is in
section 7.4.1.6. The one wire is the source of the charge current, the other
is the voltage reference line. I believe that the red line is the charge
current output while the yellow is the voltage sense but I am only basing
this on color coding conventions and the Jabiru schematics. The installation
manual shows the red wire going directly to the battery while the yellow is
on the other side of the master switch.
The reason for two separate wires is so that the sense wire "sees" that
actual voltage at the battery without any voltage drop in the charge current
wire. The reason offered for not tying the sense wire directly to the
battery is that with the engine off a very small amount of current flows
into the sense wire which could (over a long period of time) drain the
battery. But the whole point of the sense wire is to accurately sense the
voltage AT THE BATTERY to correctly charge it. So I'm inclined to tie the
two wires in question directly to the battery.
-- Craig
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