nuckolls.bob(at)aeroelect
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 Posted: Wed Jan 27, 2016 6:00 am Post subject: Difference between LR3C and SB1A Regulators |
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At 07:31 PM 1/26/2016, you wrote:
| Quote: | Thanks Bob
So, normally in flight both field lines (to MAIN ALT and to STANDBY ALT) should be On?
In this case, we can say that theoretically both alternators are producing electricity, but there’s no current flowing in the wire that comes from the “weaker” alternator? |
Pretty close . . . It's not easy to parallel two
alternators onto a single bus without special circuitry
within the regulators (not unlike the current sensor
on the B&C standby regulators) that 'steers' the two
alternators into sharing a load. More often than not,
finely tuned but independent regulators drift apart
far enough that one alternator will 'hog' the load
and the other relaxes. We wrestled with that fact
on many of the light twins in TC aviation (C336/337,
B55, C303T, etc.)
We exploited that behavior at B&C in the design of the SB
series regulators by deliberately setting the secondary
regulator 1.0 volt or so BELOW nominal bus voltage.
The behavior was predictable . . . the secondary
alternator's field voltage was suppressed to zero
and although still rotating . . . it produces no
output current.
When the main alternator quits or is shut down, bus
voltage sags and the secondary regulator wakes up
it's companion alternator. We added sensing features
unique to stand-by service to detect this awaking
to light the ALT LOADED annunciator and then to
flash it if present loads on the alternator exceeded
its ratings.
| Quote: |
And what about flying with only the MAIN ALT field switch On, and the Backup ALT field switch Off, the latter only to be flipped On by the pilot when he notices no current is flowing from the MAIN ALT?
Is this not recommended? |
Your choice. In fact . . . should you choose this
mode of operation, it is not necessary to use an
SB series regulator on the standby alternator . . .
nor do you need to adjust it to a lower set-point.
It's simply a second alternator held in reserve to
be brought on line when your ACTIVE NOTIFICATION of
LOW VOLTAGE says the #1 alternator went to sleep
or died.
We'll be exploring operational options for the
next generation of regulators with an goal of
lowering parts counts while improving/simplifying
operability. We've learned quite a lot about this
business over the last 30 years!
Bob . . .
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