finn.lassen(at)verizon.ne
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 Posted: Tue Dec 31, 2024 8:26 am Post subject: OVP relay in B+ lead bad idea |
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Thanks Joe.
I'm now thinking that the ripple spikes from the alternator (open
battery) triggered the OVP module which killed power to the relay and
also power to field winding and voltage regulator. Probably happened
fast enough for the 5A breaker not to trip. Still hard to believe that
the OVP SCR was able to pull the output small rectifier bridge in the
alternator to ground (without damaging the diodes) long enough to kill
the magnetic field.
I bench tested the alternator with a 1/2HP drill motor and it seems to
work OK. However, without battery, the ripple peaks exceed 15V+ which
would cause continuous triggering of the OVP module. (appears the
internal voltage regulator uses average rather than peak voltage).
Moral of story is still: no B+ relay. Supply field/voltage regulator
externally.
Actually, do have a backup battery!
Finn
On 11/15/2024 12:46 PM, user9253 wrote:
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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
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