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ATC slo blo?

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fvalarm(at)rapidnet.net
Guest

Posted: Wed Mar 06, 2013 8:37 pm Post subject: ATC slo blo?

Is there such a thing as a slow blow fuse in an ATC format (for a fuse

block)?



Bevan

racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Thu Mar 07, 2013 5:53 am Post subject: Re: ATC slo blo?

NO.   Slow Blow not available in ATC format.  ATC, by specification, is a fast acting low voltage automotive blade type fuse.

_________________
Jerry King

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Mar 07, 2013 5:57 am Post subject: ATC slo blo?

At 10:35 PM 3/6/2013, you wrote:

 	  Quote: 	
		  

Is there such a thing as a slow blow fuse in an ATC format (for a fuse

block)?


	


   No. What is the situation for which you perceive

   a need for such a fuse?



   Bob . . .

fvalarm(at)rapidnet.net
Guest

Posted: Thu Mar 07, 2013 9:28 am Post subject: ATC slo blo?

Hi Bob,



My P-mag manual says to use a breaker or slow blow fuse.  I have already

wired the P-mags to a fuse block (ATC) and my field of breakers is already

full.



So plan B will be to replace the switches that control the power to the

P-mags with switch-breakers (5 amp) and replace the fuses with a max high

value to protect the wire to the switch-breakers.



The fuse size to protect 18 AWG wire (about 5 foot long), 10 or 15 amp?

(fast acting ATC).



Bevan

RV7A



 



--

fvalarm(at)rapidnet.net
Guest

Posted: Thu Mar 07, 2013 10:21 am Post subject: ATC slo blo?

OK,



Maybe my memory has been fading.  To clarify, the P-mags instructions say to

use a breaker (in another area they suggest a pullable breaker) and a switch

to control power to the P-mags.  I may have got the fuse idea from the

Z-drawings for electronic ignition.  Anyway...



I currently have 5-amp fuses in the always hot battery bus feeding the P-mag

power control switches.  These switches in turn feed the power inputs of the

P-mags.



So the easy fix would be to replace the switches with a switch/breakers, and

replace the fuses protecting the feed to the switch with a higher value ATC

such as 10-15 amp.  It's a 18 AWG wire all the way from the fuse block to

the P-mags. Each P-mag has it's own independent circuit, fuse, wire and

switch.



Bob, I would like to use the highest value fuse possible ahead of the switch

breaker.  It is not supposed to trip unless the wire to the switch faults

hard.  Could this be 15 amp?

Bevan 



--

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Mar 07, 2013 12:55 pm Post subject: ATC slo blo?

At 12:19 PM 3/7/2013, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "B Tomm" <fvalarm(at)rapidnet.net>



 OK,



 Maybe my memory has been fading.  To clarify, the P-mags instructions say to

 use a breaker (in another area they suggest a pullable breaker) and a switch

 to control power to the P-mags.  I may have got the fuse idea from the

 Z-drawings for electronic ignition.  Anyway...



 I currently have 5-amp fuses in the always hot battery bus feeding the P-mag

 power control switches.  These switches in turn feed the power inputs of the

 P-mags.



 So the easy fix would be to replace the switches with a switch/breakers, and

 replace the fuses protecting the feed to the switch with a higher value ATC

 such as 10-15 amp.  It's a 18 AWG wire all the way from the fuse block to

 the P-mags. Each P-mag has it's own independent circuit, fuse, wire and

 switch.



 Bob, I would like to use the highest value fuse possible ahead of the switch

 breaker.  It is not supposed to trip unless the wire to the switch faults

 hard.  Could this be 15 amp? 	


    I think you're getting wrapped around the worry-axle my

    friend. A p-mag needs power only to get an engine started

    and to operate at idle/taxi rpms.  After that, it runs

    nicely on internal power alone.



    During any given tank full of fuel, what's the likelihood of loosing

    all 4 power sources for the pair of p-mags? They're PM alternators.

    Further, they take very little power from the bus. Ordinary 5A fuses

    to the e-bus are plenty robust.



    Referring to the Emagair literature we see:

 [img]cid:.0[/img]   



 Current draw for this system at max RPM is only 0.25 amps! There are no

 inrush currents associated powering up this system. From a systems perspective,

 they would like to have +12 available all the time. There's no reason to 'switch

 the supply on and off except to test the internal power source . . . which

 is exceedingly reliable.



 If it were my airplane, I'd run the p-mags from the e-bus through

 5A fuses and no switches. Also, 20AWG wire is plenty robust. Treat

 them just as you would a magneto for engine control and pre-flight

 testing of ignition systems.  Periodically check internal power sources

 by powering the e-bus down and make sure the engine runs at

 RPM above 1500 with the opposite system turned OFF. This checks

 internal sources. Power the e-bus back up and check to see that

 the engine will start with a single p-mag switched ON . . . then

 check the other. This will spot a 'missing' dc power path. Do it

 at each oil change interval.



 I wouldn't spend a lot of time crafting a 'golden' source of

 DC power. Risks to the aircraft and occupants due to loss of

 any one feature is zero, risk for loss of all 4 in any 4-hour

 period is vanishingly small.



 

   Bob . . .

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bicyclop(at)pacbell.net
Guest

Posted: Thu Mar 07, 2013 4:19 pm Post subject: ATC slo blo?

tim2542(at)sbcglobal.net
Guest

Posted: Thu Mar 07, 2013 8:03 pm Post subject: ATC slo blo?

Ummm, check me but I'm pretty sure the power to the PMAG is protected with a pull-able breaker or other, but it does not run power thru the switch. Also, you want the power from the switched side of the master relay not the always hot bus as you indicated because the PMAG draws power even when switched off via the P lead.

The switch operates just as a P lead to kill the ignition, but it does not interrupt power to the unit. 

A pull-able breaker is desired so you can check the internal alternator function as part of your run up. Pull the breaker, kill the other ignition and it should keep running. 

One other tip, be sure to pull the breaker when using a battery charger, PMAGs have had problems and its mentioned in the manual. 

Tim

Sent from my iPad



On Mar 7, 2013, at 10:19 AM, "B Tomm" <fvalarm(at)rapidnet.net> wrote:



 	  Quote: 	
		   

 

   Anyway...

 

 I currently have 5-amp fuses in the always hot battery bus feeding the P-mag

 power control switches.  These switches in turn feed the power inputs of the

 P-mags.

 

 So the easy fix would be to replace the switches with a switch/breakers, and

 replace the fuses protecting the feed to the switch with a higher value ATC

 such as 10-15 amp.  It's a 18 AWG wire all the way from the fuse block to

 the P-mags. Each P-mag has it's own independent circuit, fuse, wire and

 switch.

fvalarm(at)rapidnet.net
Guest

Posted: Thu Mar 07, 2013 8:07 pm Post subject: ATC slo blo?

OK,

  

 Thanks Bob,

  

 I will leave things as they.  Thanks for your  time.

  

 Bevan



   From:  owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert  L. Nuckolls, III

Sent: Thursday, March 07, 2013 12:52 PM

To:  aeroelectric-list(at)matronics.com

Subject: RE: ATC  slo blo?

 

At 12:19 PM 3/7/2013, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message    posted by: "B Tomm" <fvalarm(at)rapidnet.net>



OK,



Maybe my    memory has been fading.  To clarify, the P-mags instructions say    to

use a breaker (in another area they suggest a pullable breaker) and a    switch

to control power to the P-mags.  I may have got the fuse idea    from the

Z-drawings for electronic ignition.  Anyway...



I    currently have 5-amp fuses in the always hot battery bus feeding the    P-mag

power control switches.  These switches in turn feed the power    inputs of the

P-mags.



So the easy fix would be to replace the    switches with a switch/breakers, and

replace the fuses protecting the feed    to the switch with a higher value ATC

such as 10-15 amp.  It's a 18    AWG wire all the way from the fuse block to

the P-mags. Each P-mag has it's    own independent circuit, fuse, wire and

switch.



Bob, I would like to    use the highest value fuse possible ahead of the switch

breaker.  It    is not supposed to trip unless the wire to the switch faults

hard.     Could this be 15 amp? 	


   I think you're getting  wrapped around the worry-axle my

   friend. A p-mag needs power  only to get an engine started

   and to operate at idle/taxi  rpms.  After that, it runs

   nicely on internal power  alone.



   During any given tank full of fuel, what's the  likelihood of loosing

   all 4 power sources for the pair of  p-mags? They're PM alternators.

   Further, they take very little  power from the bus. Ordinary 5A fuses

   to the e-bus are plenty  robust.



   Referring to the Emagair literature we see:

[img]cid:593270504(at)08032013-355A[/img]    



Current draw for this system at max RPM is only 0.25 amps! There are  no

inrush currents associated powering up this system. From a systems  perspective,

they would like to have +12 available all the time. There's no  reason to 'switch

the supply on and off except to test the internal power  source . . . which

is exceedingly reliable.



If it were my airplane,  I'd run the p-mags from the e-bus through

5A fuses and no switches. Also,  20AWG wire is plenty robust. Treat

them just as you would a magneto for  engine control and pre-flight

testing of ignition systems.  Periodically  check internal power sources

by powering the e-bus down and make sure the  engine runs at

RPM above 1500 with the opposite system turned OFF. This  checks

internal sources. Power the e-bus back up and check to see that

the  engine will start with a single p-mag switched ON . . . then

check the other.  This will spot a 'missing' dc power path. Do it

at each oil change  interval.



I wouldn't spend a lot of time crafting a 'golden' source  of

DC power. Risks to the aircraft and occupants due to loss of

any one  feature is zero, risk for loss of all 4 in any 4-hour

period is vanishingly  small.



 

  Bob . . .

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Viewed:

6113 Time(s)

fvalarm(at)rapidnet.net
Guest

Posted: Thu Mar 07, 2013 9:13 pm Post subject: ATC slo blo?

Thanks Tim.



I understand the drawing from Emagair, and Bob's comment makes sense to me.



I have a very non-standard (comprehensive) electrical system.  It includes a

very small always hot bus located 6 inches from the battery.  This bus

supplies power (via two independent circuits) to the P-mag power switches,

not to be confused with the magneto kill switches (which are part of the

keyed ignition).  These switches must be turned on or the engine will not

start.  These switches are the ones you would turn off to test the internal

alternators (periodically, not on each runup).  They are also turned off at

the end of flight, otherwise the battery will run down.  



This is how I have chosen to build my system and flows well with the rest of

my electrical system.  I know it is not for everyone, but I have like the

way I have it.



My original question came up as I was told (and I believed) that the P-mags

should have a breaker/switch and not fuse/switch. With the very small

current flows according to Bob M, (the Emagair spec sheet does not indicate

current flow), and no unusually high inrush currents, fuses should be fine

as long as I also have switches to power down the mags.



On the other hand, my WigWag module (by Sound Off Signal) is solid state and

does require a fast acting fuse to protect the controller portion, but

that's a story for another day.



Bevan

--

tim2542(at)sbcglobal.net
Guest

Posted: Thu Mar 07, 2013 9:47 pm Post subject: ATC slo blo?

Oh I see, sounds like we're on the same page then. I thought you were leaving them powered up from the way I read it.

Tim

Sent from my iPad



On Mar 7, 2013, at 9:12 PM, "B Tomm" <fvalarm(at)rapidnet.net> wrote:



[quote] 

 

 Thanks Tim.

 

 I understand the drawing from Emagair, and Bob's comment makes sense to me.

 

 I have a very non-standard (comprehensive) electrical system.  It includes a

 very small always hot bus located 6 inches from the battery.  This bus

 supplies power (via two independent circuits) to the P-mag power switches,

 not to be confused with the magneto kill switches (which are part of the

 keyed ignition).  These switches must be turned on or the engine will not

 start.  These switches are the ones you would turn off to test the internal

 alternators (periodically, not on each runup).  They are also turned off at

 the end of flight, otherwise the battery will run down.  

 

 This is how I have chosen to build my system and flows well with the rest of

 my electrical system.  I know it is not for everyone, but I have like the

 way I have it.

 

 My original question came up as I was told (and I believed) that the P-mags

 should have a breaker/switch and not fuse/switch. With the very small

 current flows according to Bob M, (the Emagair spec sheet does not indicate

 current flow), and no unusually high inrush currents, fuses should be fine

 as long as I also have switches to power down the mags.

 

 On the other hand, my WigWag module (by Sound Off Signal) is solid state and

 does require a fast acting fuse to protect the controller portion, but

 that's a story for another day.

 

 Bevan

 

 

 --

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Mar 08, 2013 6:26 am Post subject: ATC slo blo?

 	  Quote: 	
		  

My original question came up as I was told (and I believed) that the P-mags

should have a breaker/switch and not fuse/switch.


	


    The circuit protection philosophy and the means by

    the circuit is controlled are separate issues. The

    Emagair drawing suggests they might be combined but

    it's one of many options.



    The only utility for the switch is to be able to test

    internal power for the emag . . . which means seeing

    if the engine will run from a single mag that has been

    deprived of battery power. This suggests that the

    power path be controllable. Obviously, one can kill

    the bus by simply turning the battery switch off. So

    doing a periodic test of internal power for the Emags

    is no big deal if one chooses to leave the suggested

    switches out.



    As a separate consideration, protecting any wire that's

    tied to a high fault current source (alternator/battery

    fed busses) is worthy of protection. Breakers or fuses

    of several types may be considered in the development

    personal design goals.



 	  Quote: 	
		  With the very small

current flows according to Bob M, (the Emagair spec sheet does not indicate

current flow),


	


   Note 4 of the image I purloined from the Emagair website

   states a 20 mA idle current and 0.25A max running current.



 	  Quote: 	
		    and no unusually high inrush currents, fuses should be fine

as long as I also have switches to power down the mags.


	


   What is your perception of need to "power down" the mags

   by any means other than simply turning the 'mag switch' to

   off?



   Note 2 of the same image states that the DC supply is

   switched only for the purposes of testing internal

   power feature on p-mags. Just how that power is removed

   is open to the spirit and intent of design goals. Given

   the inherent reliability of the internal sources combined

   with the fact that each source is but one of four sources,

   any one of which will fly the airplane, the need for

   counting all your marbles before each flight is unnecessary.



   It follows that adding more switches on the panel for

   the convenience of conducting a periodic test only

   drives up parts count and relative panel clutter.



 	  Quote: 	
		  On the other hand, my WigWag module (by Sound Off Signal) is solid state and

does require a fast acting fuse to protect the controller portion, but

that's a story for another day.


	


   Fuses to protect hardware? Can you direct me to the

   citation?

   Bob . . .

fvalarm(at)rapidnet.net
Guest

Posted: Fri Mar 08, 2013 10:02 am Post subject: ATC slo blo?

Thanks Bob,



   Fuses to protect hardware? Can you direct me to the

   citation?



See the paragraph titled "WARNING".



http://sos-production.s3.amazonaws.com/images/ETHDSS-SP%20Fold%20A.pdf



It calls for fast a acting fuse, not a fusible link,  slow blow or circuit

breaker.



Bevan

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Mar 08, 2013 10:33 am Post subject: ATC slo blo?

At 12:01 PM 3/8/2013, you wrote:

 	  Quote: 	
		  

Thanks Bob,



    Fuses to protect hardware? Can you direct me to the

    citation?



See the paragraph titled "WARNING".



http://sos-production.s3.amazonaws.com/images/ETHDSS-SP%20Fold%20A.pdf



It calls for fast a acting fuse, not a fusible link,  slow blow or circuit

breaker.


	


   Interesting. Thanks!

   Bob . . .

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