Today's Message Index:
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1. 06:21 PM - Re: Re: OVP relay in B+ lead bad idea -- corrected (Finn Lassen)
2. 06:37 PM - Re: Re: OVP relay in B+ lead bad idea -- corrected (Finn Lassen)
3. 06:48 PM - Re: Re: OVP relay in B+ lead bad idea -- corrected (Finn Lassen)
Message 1
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| Subject: | Re: OVP relay in B+ lead bad idea -- corrected |
I just spotted the terrible error in the the Z-24 diagram in the
Adapting_IR_Alternators_to_Aircraft.pdf document I have!
It shows the alternator F-terminal connected to overvoltage relay power
which is pulled to ground when OVP activates.
In case of a nuisance trip you now have killed the field in the
alternator, and if you have a battery failed open, there is no battery
to provide startup voltage to the alternator after resetting the
breaker. That's what took my plane down.
If F is the internal regulator startup/sense terminal it should be
connected to B+. (Any Alternator Warning relay terminal -- typically
connected to positive side of field winding -- can be left unused.)
I would also recommend a 30,000uF or bigger capacitor from B+ to ground.
That should provide sufficiently low ripple and noise power for the
alternator and its internal regulator with no (failed open or
disconnected) battery.
Finn
On 11/15/2024 12:46 PM, user9253 wrote:
>
> It takes a lot less voltage and current to hold a relay closed than it does to
first energize it.
> Just because a circuit breaker is marked "5A" doesn't necessarily mean that it
will trip at exactly 5 amps.
> It should be bench tested with an adjustable current power supply. It might
be tripping at much less than
> 5 amps. A loose connection will generate heat which can result in a breaker
tripping at
> less than its rated current. The alternator field circuit breaker should not
be tripping.
> -
> Good job making a forced landing and walking away. Many pilots panic when
the engine
> quits and pull back on the stick to avoid going down. The wings stall with fatal
results.
> The ground doesn't give. Bob Hoover quote:
> "If you're faced with a forced landing, fly the thing as far into the crash
as possible."
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=514526#514526
>
>
Message 2
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| Subject: | Re: OVP relay in B+ lead bad idea -- corrected |
Attached is what I think is the correct way to overvoltage protect an
automotive internally regulated alternator with a relay in the B+ lead.
Finn
Message 3
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| Subject: | Re: OVP relay in B+ lead bad idea -- corrected |
Fixed attachment!
Attached is what I think is the correct way to overvoltage protect an
automotive internally regulated alternator with a relay in the B+ lead.
Finn
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