Today's Message Index:
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1. 10:00 PM - OV protection circuit design (Pat Little)
2. 10:01 PM - Connecting small wire to large terminal (Lyn Robertson)
Message 1
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| Subject: | OV protection circuit design |
I'm designing the electrical system for my aircraft (a Zenith STOL CH750)
based on Z-12 (dual alternator, single battery). The primary alternator is
a B&C SD-20 controlled by their LR3C. The stby alt is the PM unit built
into the Jabiru 3300 engine, and which is managed by a "kubota" style
regulator as supplied with the Jabiru firewall-forward kit.
The LR-3 contains an OV protection mechanism which will protect against the
SD-20 going postal, whereas for the stby alt it will be a separate OV
Module. In each case the OV protection shorts the supply to ground and
trips a 5A CB. Most of the Z figures show a fuselink at the bus, which I
presume is to protect the segment of wire between the bus and the circuit
breaker.
The Z diagrams show a variety of wire sizes in the OV circuit (for example,
Z-20 shows 16, 20, and 22AWG segments all in series) while others (e.g.,
Z-12) show consistent AWG throughout. I can't figure out why they vary so
much, and I'm hoping I can get some feedback on my preliminary design. Here
is what I am thinking:
[image: image.png]
I sized the main alt wires based on B&C's LR3C wiring diagram which shows
18AWG for the field circuit.
The power wire sizes for the stby alt are taken from Z-20, and the stby
control circuit is sized based on the 20AWG wires on the B&C OVM-14 module
(and availability of their 24AWG fuselink kit). The relay draws 0.5A.
I'd appreciate any comments.
Thanks.
Message 2
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| Subject: | Connecting small wire to large terminal |
I am building an RV14A and plan to install dual P-mags. In the drawings,
power for the P-mags is shown as coming directly from the switched side of
the master solenoid. The problem is that the supply wire is 20 gauge and
the solenoid terminal is a 5/16=9D stud. I have been unable to find a
ring
terminal connector that will fit both the wire and the solenoid terminal.
Currently, the only thing on the master solenoid terminal is a 1/2=9D
x0.060
solid copper buss bar about 4=9D long that connects to the starter so
lenoid.
This easiest solution seems to be to drill a hole in the buss bar and
connect the P-mag lead to it with #6 hardware. Does anyone see any
problem with this? I guess I should mention that I am using the Advanced
Control Module (ACM) with electronic circuit breakers from Advanced Flight
Systems for power distribution and, as a result, don=99t have direct
access
to the main buss as I would in a more conventional design. Access to power
upstream of the ACM is limited to the master solenoid location mentioned or
at the input power connection to the ACM itself.
Any advice is greatly appreciated. Thanks!
Lyn Robertson
Corvallis, OR
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