Today's Message Index:
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1. 09:44 AM - Alternators - To Fuse or not to fuse - That IS the question (kearney)
2. 10:11 AM - Re: Alternators - To Fuse or not to fuse - That IS the question (Sebastien)
3. 03:14 PM - Re: Alternators - To Fuse or not to fuse - That IS the question (user9253)
4. 03:50 PM - Re: Alternators - To Fuse or not to fuse - That IS the question (kearney)
5. 05:48 PM - Re: Alternators - To Fuse or not to fuse - That IS the question (user9253)
6. 06:14 PM - Re: Re: Alternators - To Fuse or not to fuse - That IS the question (Jared Yates)
7. 06:27 PM - Re: Re: Alternators - To Fuse or not to fuse - That IS the question (David Saylor)
8. 09:02 PM - Re: Re: Alternators - To Fuse or not to fuse - That IS the question (Charlie England)
Message 1
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Subject: | Alternators - To Fuse or not to fuse - That IS the |
question
Bib et Al
I have been reading with interest your monographs on fuses and circuit breakers.
I had always thought that CBs were "modern" and fuses were "old school".
So this brings me to an alternator wiring question. Keep in mind this is based
on the Z12 architecture with an electrically dependent engine - EFI/EI.
The questions is: why would I use a CB on the primary and backup alternator field
circuits?
My rational for thing this is, if the alternator field circuit pops, something
is wrong, likely with the alternator. With the Z12 architecture, the backup alternator
should immediately come on line and keep me, the electro-goodies and
the engine happy. Why would I ever want to push that breaker back in?.
If the backup alternator field CB then also pops, I would then think that something
is very seriously amiss. Again, why would I ever want to reset that breaker.
In theory I would still have the battery to get me *somewhere* safely albeit with
urgency.
Inquiring minds need to know.
Cheers
Les
PS: The above assumes that my post start checks confirms normal operation of both
alternators.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=471791#471791
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Subject: | Re: Alternators - To Fuse or not to fuse - That IS |
the question
The conundrum lies in your assumptions. You are assuming that if the field
circuit breaker pops something must be wrong with the alternator system.
Not necessarily the case. I'll leave it to others with more understanding
of such things to elaborate.
On Sat, Aug 12, 2017 at 9:41 AM, kearney <kearney@shaw.ca> wrote:
>
> Bib et Al
>
> I have been reading with interest your monographs on fuses and circuit
> breakers. I had always thought that CBs were "modern" and fuses were "old
> school".
>
> So this brings me to an alternator wiring question. Keep in mind this is
> based on the Z12 architecture with an electrically dependent engine -
> EFI/EI.
>
> The questions is: why would I use a CB on the primary and backup
> alternator field circuits?
>
> My rational for thing this is, if the alternator field circuit pops,
> something is wrong, likely with the alternator. With the Z12 architecture,
> the backup alternator should immediately come on line and keep me, the
> electro-goodies and the engine happy. Why would I ever want to push that
> breaker back in?.
>
> If the backup alternator field CB then also pops, I would then think that
> something is very seriously amiss. Again, why would I ever want to reset
> that breaker.
>
> In theory I would still have the battery to get me *somewhere* safely
> albeit with urgency.
>
> Inquiring minds need to know.
>
> Cheers
>
> Les
>
> PS: The above assumes that my post start checks confirms normal operation
> of both alternators.
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=471791#471791
>
>
Message 3
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Subject: | Re: Alternators - To Fuse or not to fuse - That IS |
the question
If you are using Z-12, neither of the alternator primary "B" leads have circuit
breakers. One has an ANL fuse and the other has a fuse link. I believe that
Bob now recommends fuses instead of fuse links. Regardless, I would use a 30
amp fuse for the smaller alternator "B" lead. The purpose of those fuses is
to protect the battery and wires from a short circuit, NOT to protect the alternators.
Alternators limit their own current. They are not capable of putting
out much more than their rated current.
Some crowbar types of over voltage protection circuits have been known to nuisance
trip the breaker or fuse. Thus circuit breakers may be used so that they
can be reset in case they nuisance trip.
Some builders have elected to not install over voltage protection. In that case,
fuses may be used. Most modern avionics are rated for 10 to 30 volts. Over
voltage might not be as much of a concern as it once was. On the other hand,
if an Earth-X battery is installed, it will disconnect itself from the electrical
system if the voltage goes high. Without a battery to help limit the
over voltage, even modern avionics are at risk of being damaged.
I spoke with an Earth-X representative at OSH. She recommended that the aircraft
electrical system have over voltage protection to protect avionics. The
Earth-X battery has its own built-in protection.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=471796#471796
Message 4
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Subject: | Re: Alternators - To Fuse or not to fuse - That IS |
the question
Hi Joe
Thanks for the response. However, the CBs I was referring to are located on the
alternator FIELD circuits not the B Leads.
I understand about the ANL fuses on the B Leads and plan to comply with the Z12
architechure in that respect.
Also, to follow up on your comment on a nuisance trip, if a trip occurs, resetting
a breaker to confirm that it was indeed a nuisance trip may be risky. If the
problem is genuine, resetting the breaker may cause smoke to come out of wires.....
If this logic is correct, then why wouldn't it be *better* to simply use 5A fuses
rather than CB's for the Z12.
Cheers
Les
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=471799#471799
Message 5
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Subject: | Re: Alternators - To Fuse or not to fuse - That IS |
the question
Les,
Sorry I misread your post and mistakenly interpreted "primary" as the alternator
stator winding.
The field current on some alternators can be as much as 5 amps when under heavy
load. Perhaps a 7.5 amp fuse would be better for the main alternator field.
5 amps should be good for the smaller backup alternator field.
Eric Jones at Perihelion Design sells over voltage protection that opens the alternator
field circuit without shorting it to ground. No blown fuses or popped
circuit breakers.
http://www.periheliondesign.com/lovm.htm
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=471805#471805
Message 6
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Subject: | Re: Alternators - To Fuse or not to fuse - That |
IS the question
I use the breaker in lieu of a switch for the alternator field, should I
want to manually disconnect it. If I was to use a fuse, I'd have to also
install a switch.
On August 12, 2017 18:55:03 "kearney" <kearney@shaw.ca> wrote:
>
> Hi Joe
>
> Thanks for the response. However, the CBs I was referring to are located on
> the alternator FIELD circuits not the B Leads.
>
> I understand about the ANL fuses on the B Leads and plan to comply with the
> Z12 architechure in that respect.
>
> Also, to follow up on your comment on a nuisance trip, if a trip occurs,
> resetting a breaker to confirm that it was indeed a nuisance trip may be
> risky. If the problem is genuine, resetting the breaker may cause smoke to
> come out of wires.....
>
> If this logic is correct, then why wouldn't it be *better* to simply use 5A
> fuses rather than CB's for the Z12.
>
> Cheers
>
> Les
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=471799#471799
>
>
Message 7
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Subject: | Re: Alternators - To Fuse or not to fuse - That |
IS the question
A pullable breaker on the field is more functional than a fuse since the
field draws a lot of current when the engine's not running (the alternator
gets hot enough to leave a mark...). I pull the breaker if I have the
master on for any length of time.
--Dave
On Sat, Aug 12, 2017 at 6:11 PM, Jared Yates <email@jaredyates.com> wrote:
> >
>
> I use the breaker in lieu of a switch for the alternator field, should I
> want to manually disconnect it. If I was to use a fuse, I'd have to also
> install a switch.
>
>
> On August 12, 2017 18:55:03 "kearney" <kearney@shaw.ca> wrote:
>
>>
>> Hi Joe
>>
>> Thanks for the response. However, the CBs I was referring to are located
>> on the alternator FIELD circuits not the B Leads.
>>
>> I understand about the ANL fuses on the B Leads and plan to comply with
>> the Z12 architechure in that respect.
>>
>> Also, to follow up on your comment on a nuisance trip, if a trip occurs,
>> resetting a breaker to confirm that it was indeed a nuisance trip may be
>> risky. If the problem is genuine, resetting the breaker may cause smoke to
>> come out of wires.....
>>
>> If this logic is correct, then why wouldn't it be *better* to simply use
>> 5A fuses rather than CB's for the Z12.
>>
>> Cheers
>>
>> Les
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=471799#471799
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
Message 8
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Subject: | Re: Alternators - To Fuse or not to fuse - That |
IS the question
Les, I think the 'nuisance trips' idea refers to the overvoltage
protection module tripping the field breaker when there is a very short
term excursion above the modules voltage set point. This can
occasionally happen when there's no actual danger to the system from
overvoltage. A fuse makes recovery a lot more...inconvenient.
Charlie
On 8/12/2017 5:47 PM, kearney wrote:
>
> Hi Joe
>
> Thanks for the response. However, the CBs I was referring to are located on the
alternator FIELD circuits not the B Leads.
>
> I understand about the ANL fuses on the B Leads and plan to comply with the Z12
architechure in that respect.
>
> Also, to follow up on your comment on a nuisance trip, if a trip occurs, resetting
a breaker to confirm that it was indeed a nuisance trip may be risky. If
the problem is genuine, resetting the breaker may cause smoke to come out of
wires.....
>
> If this logic is correct, then why wouldn't it be *better* to simply use 5A fuses
rather than CB's for the Z12.
>
> Cheers
>
> Les
>
---
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