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1. 12:51 AM - Re: Re: Jabiru electric circuit design, your comments?? (Rob Turk)
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| Subject: | Re: Jabiru electric circuit design, your comments?? |
Hi Ralph,
Thanks for your analysis. I think you have a point with the regulator
sense wire, except Jabiru do not seem to practice what they preach.
Looking at their schematics for the J160 Certified (3300 Installation
Manual JEM3302-4) they have the regulator output direct to the battery,
but the sense wire goes to the main bus bar, behind a 15A fuse and a
toggle switch. Essentially the same as I do, except I use a battery
contactor instead of a toggle switch.
One thing I do not know is what the regulator output will do when it's
disconnected. It may go to full output as you suggest, or it may go to
zero. The capacitor is rated at 40V, so even a full output situation
should not cause any issues. Perhaps I should use a double-pole
alternator relay and disconnect one of the A/C wires as well.
As for the OVM crowbar, it is connected directly across the alternator
relay. Its placement is such that when the alternator circuit is
connected, the OVM senses the power across main bus and (through S1 and
S2) ground. If S1 or S2 opens, the alternator relay will open as well.
If an over-voltage occurs, the OVM crowbar will short-circuit. This will
open S2 (automatic circuit breaker) and disconnect the alternator
circuit. This is exactly what AeroElectric does. Once the alternator
relay is open, there are no other sources that can elevate the voltage
above the battery level.
I'd appreciate your suggestions for a better placement of the OVM.
Rob
On 10/30/2010 3:10 AM, jetboy wrote:
> --> JabiruEngine-List message posted by: "jetboy"<sanson.r@xtra.co.nz>
>
> I don't wish to over-analyze your schematic, however there are some features
that need clarity;
>
>
> The alternator contactor, rel.3 does not disconnect the AC from the regulator.
>
>
> If the alternator contactor is open, depending upon the DC bus voltage at the
time, the voltage applied to your capacitor will be more than 40 Volts, and it
might not do nice things to your equipment when the contacts close.
> Jabiru manual states the regulator output and sense wires should be tied together
at all times, to prevent this possibility.
>
> Think what might happen if you open the master switch, and the main contactor
is open, and there is more than 6 volts difference between the batt volts and
the DC bus volts. Will Rel.3 coil be energised via rel.1 coil and the battery
connection? do you want this to happen?
>
> The placement of the OVM crowbar module does not look appropriate to me.
>
> I prefer either of 2 published wiring systems; the Jabiru way or the Aerolectric
way, both are acceptable practice for homebuilt aircraft, its when a hybrid
system is attempted that unexpected consequences could result.
>
> Ralph
>
> --------
> Ralph - CH701 / 2200a
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=317448#317448
>
>
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