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Hi Tommy,
Here is the information from my aircraft data base:
I got the parts from Radio shack back a few years ago, I don't think the
values are critical but should be fairly close especially on diode working
voltage and current. My understanding of the circuit is that while the
alterntor is not turning, current will flow throught the "L" wire and in the
car would cause the relay to close and illuminate a warning light. Once the
alternator starts producing voltage, it back biases the diode and prevents
current in the "L" wire from flowing, causing the relay to open and warning
light to go out.
I just use the relay for the resistance of its coils, not certain that it is
required. Might just want to try the diode perhaps with a 50 ohm, 2 watt
resistor to reduce initial surge through diode.
Hope this helps. Ed Anderson
Electrical Components
Charging System::
Automobile Alternator with internal voltage regulator.
Type: Alternator: Bosche, 70 Amp, Integrated Voltage Regulator
Relay: 30 Amp Auto Relay. Radio Shack Part # 275-226
Coil Voltage: 12V, Pull-In Voltage: 6V, Coil Resistance: 66 Ohms,
Nominal Current: 160 ma, Drop-Out Voltage: 3.6V
Relay contacts:
SPST Contacts: 30A at 12VDC. Pin 85 Grd, 88 on/off switch, 30/51
12Vout,
87 12Vin.
Diode: 6 Amp Rectifier Diode. Radio Shack Part# 275-1661.
TA=24C, VRM(rep), VRM(wkg), VR: 50 VPK
VRM (non-rep):100, Vr:35, Io: 6 Amps at 60C, TjTstg: -65=174C,
VF(AV):0.9VPK, IR(AV): 25uAdc.
CBK: 5 amp circuit breaker in field coil
NOTE: Relay and diode are installed between ignition switch and alternator
warning circuit. Base of diode toward alternator "L" terminal and in series
with the relay (if you use one). .
Tommy, This is what I am flying with, but must admit that I have never tired
the alternator without the diode so can't state with certaintly that it is
required. I looked at the alternator diagram in the Haynes book. It looks
like the "L" voltage may back-bias some diodes internal to the alternator
that feed the field coil but I am not certain (not up on my transistors and
diodes in alternators). But, once the alternator starts producing voltage
(greater than battery voltage) it looks like that would then back-biase the
"L" diode and cut off current to the relay. If that is not the case then
and it would appear that all the "L" connection is just there to turn on
the warning light. Once the alternator is producing voltage, it appears to
back bias the diode causing current throught the "L" wire and relay to stop
flowing permitting the relay to open and the "Warning" light to go out.
Ed Anderson
----- Original Message -----
From: "Marvin Kaye" <marv@lancaironline.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, February 09, 2003 8:34 PM
Subject: [FlyRotary] Re: Alternator problem
> Posted for "Tommy James" <tj@healed.org>:
>
> HI Ed, Can you give advice on where to obtain a check relay or diode or
what
> ever, to make this work?
> Thanks,
> Tommy<><
>
> >>>
> Seems I recall that I needed a diode in the "L" line (I also had the relay
> coil as does Tracy). I don't have the wiring diagram, but for some reason
> it sticks in my mind that the diode was necessary.
> <<<
>
> >> Homepage: http://www.flyrotary.com/
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