Today's Message Index:
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1. 08:31 AM - Z8 scrapped . . . (Robert L. Nuckolls, III)
2. 08:46 AM - Z8 scrapped . . . (Robert L. Nuckolls, III)
Message 1
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| Subject: | Z8 scrapped . . . |
I've been wrestling with the design goals for
tying two alternators to their own dedicated
battery busses and then tying one or both
to a main bus.
Alternators using B&C alternator controllers
are not suited to this idea at all. They're
marginally okay if one of the alternators is
the SD-20 with an SB-1 regulator set to "relax"
the SD-20 when the main alternator is functional
(al la Z-12). But managing the input terminals
to the alternator controllers from an always
hot battery bus adds more poles to a DC
MASTER switch or adds complexity to the system
when handled with multiple switches . . . with
an attendant risk of mis-positioned switches
causing mis-behaviors.
There's also the issue of compliance with the
legacy "switches-off, max-cold" philosophy
for fat wires. The design demands either
b-lead disconnect contactors or fat diodes
on heat sinks.
The design looks better with internally regulated
alternators because they don't have the LV warning
systems and they do regulated voltage sensing
internally at the b-lead. But this demands b-lead
contactors as opposed to b-lead diodes because
the voltage drop across the diode cannot be
compensated for by sensing bus volts downstream
of the diode. So one COULD do some Z24-like
implementations of two alternators driving
dedicated batteries . . . but we still have
paralleling issues and increased pilot workload
to properly position switches.
The system was looking like we needed 5 contactors
total. 2 battery, 2 b-lead, 1 starter.
Finally, with the Z-8 dual-battery/dual-alternator
configuration, you can't have both alternators
driving the main bus at the same time . . . because
of load sharing issues. So this means that while
you can have both alternators running to support
their respective flying loads, only one can be
connected to the main bus at a time.
If one wants two, capable alternators and two
batteries, then Z-14 is still the architecture
of choice offering totally independent systems
with cross-tie capabilities. Z-13/8 is still the
elegant choice for low-cost, light-weight,
simple-operation.
This has been a useful exercise in that it validates
the work already published and illuminated the
messiness of what was initially perceived as another
recipe for success.
My recommendations for optimizing Noah's adaptation
of an SD-20 into his project is replace the SB-1
regulator with a generic "ford" style regulator,
add a b-lead contactor to implement fat-wire
disconnection when parked. Take field power/
voltage sensing directly from the battery bus
through a fusible link then to 5A breaker, crowbar
ovm and then to contactor+regulator bus
connection. Placard the system against
simultaneous operation of both alternators.
Bob . . .
Message 2
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| Subject: | Z8 scrapped . . . |
My recommendations for optimizing Noah's adaptation
of an SD-20 into his project is replace the SB-1
regulator with a generic "ford" style regulator,
add a b-lead contactor to implement fat-wire
disconnection when parked. Take field power/
voltage sensing directly from the battery bus
through a fusible link then to 5A breaker, crowbar
ovm and then to contactor+regulator bus
connection. Placard the system against
simultaneous operation of both alternators.
ALTERNATIVELY
Consider going to Z-14. Use aux battery consistent
with experimentation to deduce smallest
satisfactory performance. Set the SB-1
up to 14.4 volts.
Bob . . .
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