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EXP 2 Bus workaround
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nuckolls.bob(at)aeroelect
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PostPosted: Sun Oct 27, 2013 10:14 am    Post subject: EXP 2 Bus workaround Reply with quote

At 11:53 AM 10/27/2013, you wrote:
Quote:


Bob,
What are your thoughts on having a separate switch for the
alternator field versus using the second half of a double pole master switch?

Depends on how well the alternator performs without
a battery. It would be nice to have it run independently
of the battery.

Quote:
I know that your designs use a progressive transfer switch with
the center position battery only with the alternator off. But I am
thinking about the EXP2Bus (or any electrical system) that does not
have the progressive transfer switch, just a common DPDT
switch. Assuming the pilot has a plan B, for instance an E-Bus,
she could shut off the one DPDT Master-Alt switch in the event of
an alternator failure. Most likely the pilot will want the master
off anyway to conserve the battery.

The ideas behind the e-bus was to offer a means by
which everything not needed during en route flight,
i.e. cruising for an hour or more watching the ground
go by. This includes the battery contactor which
draws .8 to 1.0 amps by itself . . . as much as one
or two more radios.

Quote:
Or is it better to have a separate Alt switch?


It's nice to turn battery on leaving alternator
off for ground ops. A non-rotating alternator
draws about 3A of field current and gets hot.

When the system is fitted with crowbar ov protection,
then there's a circuit breaker that can be pulled to
disable the alternator for maintenance.

Some of my earlier drawings were dpdt bat/alt switch
+ circuit breaker. But there was such a love affair
going on over the split rocker switch that I decided
to describe a replacement for the same functionality
in a toggle switch.

Whether or not a separate switch is advised is predicated
on alternator performance sans battery.
Bob . . .


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Bob McC



Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

PostPosted: Sun Oct 27, 2013 10:37 am    Post subject: EXP 2 Bus workaround Reply with quote

If the prop is windmilling then the starter isn’t needed for a restart. All you need is to provide fuel and spark, it already turning.

Bob McC


From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Sacha
Sent: Sunday, October 27, 2013 2:05 PM
To: aeroelectric-list(at)matronics.com
Subject: Re: AeroElectric-List: Re: EXP 2 Bus workaround




Quote:
Quote:
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If you're willing to have an always hot feeder to a
starter contactor . . .
Quote:
That doesn't sound very safe when you're on he ground. Keys are out, master etc off, someone is by the prop and someone else accidentally actuates the starter by pushing the starter button or whatever. Even if the engine doesn't start you can still do some damage.

That is not the case, with the master off you will not be able to crank as the coil circuit for starter contactor will not be powered. See dwg.









You're correct, sorry I spoke before i took a look at the actual circuit.



Sacha



Ps. What is the issue with wether the prop windmills or stops? Is it that the engine is easier to restart if the prop is windmilling?
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That doesn't sound very safe when you're on he ground. Keys are out, master etc off, someone is by the prop and someone else accidentally actuates the starter by pushing the starter button or whatever. Even if the engine doesn't start you can still do some damage.

That is not the case, with the master off you will not be able to crank as the coil circuit for starter contactor will not be powered. See dwg.
0
Quote:
That doesn't sound very safe when you're on he ground. Keys are out, master etc off, someone is by the prop and someone else accidentally actuates the starter by pushing the starter button or whatever. Even if the engine doesn't start you can still do some damage.

That is not the case, with the master off you will not be able to crank as the coil circuit for starter contactor will not be powered. See dwg.
1
Quote:
That doesn't sound very safe when you're on he ground. Keys are out, master etc off, someone is by the prop and someone else accidentally actuates the starter by pushing the starter button or whatever. Even if the engine doesn't start you can still do some damage.

That is not the case, with the master off you will not be able to crank as the coil circuit for starter contactor will not be powered. See dwg.
2

[quote][b]


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Bob McC
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(just starting)
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PostPosted: Mon Oct 28, 2013 12:48 pm    Post subject: EXP 2 Bus workaround Reply with quote

If the prop is windmilling then the starter isn't needed for a
restart. All you need is to provide fuel and spark, it already turning.
OK, thanks, it makes sense to me now.
Sacha

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nuckollsr



Joined: 24 Mar 2009
Posts: 95
Location: Medicine Lodge, KS

PostPosted: Tue Nov 19, 2013 7:03 am    Post subject: Re: EXP 2 Bus workaround Reply with quote

Fred, I think we left this study dangling for lack of a list of proposed loads on your ship's bus structures. Have you had time to consider this? Doesn't need to be a drawing, just a text listing of each load . . . perhaps grouped by supply bus.

Bob . . .


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