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in-rush limiters

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Erich_Weaver(at)URSCorp.c
Guest

Posted: Thu Aug 31, 2006 12:18 am Post subject: in-rush limiters

I am considering installing in-rush limiters for my landing  lights.  Can

in-rush limiters be used effectively in conjunction with a wig-wag flasher?



My understanding is that the in-rush limiters do their job through their

odd property of providing decreasing resistance with increasing heat.  That

would imply that they would need time to cool down before being able to do

their job the next time the power is turned on.  With the flasher however,

the power is being turned on and off very quickly. On the other hand, the

bulb filament is probably not cooling off a lot either between flashes, so

maybe the in-rush limiters do not need to be effective when the wig-wag is

wigging and wagging.



Did I just answer my own question? If so, can someone  recommend an

appropriate in-rush limiter for my 12V, 75W halogen lights



thanks



Erich Weaver

nuckollsr(at)cox.net
Guest

Posted: Thu Aug 31, 2006 3:06 am Post subject: in-rush limiters

At 05:06 PM 8/30/2006 -0700, you wrote:



 	  Quote: 	
		  

I am considering installing in-rush limiters for my landing  lights.  Can

in-rush limiters be used effectively in conjunction with a wig-wag flasher?



My understanding is that the in-rush limiters do their job through their

odd property of providing decreasing resistance with increasing heat.  That

would imply that they would need time to cool down before being able to do

their job the next time the power is turned on.  With the flasher however,

the power is being turned on and off very quickly. On the other hand, the

bulb filament is probably not cooling off a lot either between flashes, so

maybe the in-rush limiters do not need to be effective when the wig-wag is

wigging and wagging.



Did I just answer my own question? If so, can someone  recommend an

appropriate in-rush limiter for my 12V, 75W halogen lights


	


      The inrush limiters are, as you've already guessed,

      slow to respond. They have to cool down for perhaps a minute

      or more to be an effective inrush limiter for the next

      turn-on event.



      At the same time, filaments in lamps . . . especially the

      halogens have a cooling time constant so long as to eliminate

      the need for current limiting between flashes of a wig-wag system



      I did some measurements on the bench a few years ago to

      flash an automotive halogen headlamp bulb. The first turn-on

      transient was what you would have expected . . . light up

      transient from cold start was about a 10x running current.



      However, sufficient heat was retained between flashes that

      subsequent turn-on events were perhaps 1.2x running current.



      Before halogens, the notion of installing inrush limiters

      or adding some kind of keepwarm circuit had some appeal. With

      the proliferation of the much more rugged halogens, the

      old life-enhancing techniques are less useful. The next revision

      of the 'Connection's lighting chapter will only mention these

      techniques as ideas with historical significance but not

      recommended for new design.



      Bob . . .



      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

FLYaDIVE(at)aol.com
Guest

Posted: Thu Aug 31, 2006 4:03 am Post subject: in-rush limiters

In a message dated 8/31/06 4:20:49 AM Eastern Daylight Time, 

Erich_Weaver(at)URSCorp.com writes:



 	  Quote: 	
		   I am considering installing in-rush limiters for my landing  lights.  Can

  in-rush limiters be used effectively in conjunction with a wig-wag flasher?

  

  My understanding is that the in-rush limiters do their job through their

  odd property of providing decreasing resistance with increasing heat.  That

  would imply that they would need time to cool down before being able to do

  their job the next time the power is turned on.  With the flasher however,

  the power is being turned on and off very quickly. On the other hand, the

  bulb filament is probably not cooling off a lot either between flashes, so

  maybe the in-rush limiters do not need to be effective when the wig-wag is

  wigging and wagging.

  

  Did I just answer my own question? If so, can someone  recommend an

  appropriate in-rush limiter for my 12V, 75W halogen lights

  

  thanks

  

  Erich Weaver

===================================
	


Erich:



I am familiar with two types of inrush limiters.  Neither of them work off of 

heat (I would like to learn more about this heat type).

The simplest "limiter" you can build yourself.  It is nothing more than a 

coil.  The coil can be made around either a dowel or a ferrite slug.  The wire 

size is chosen to handle the current of the load and the basic size is about 

1/2" ID, 1" OD and 2" Long.  The type of wire is SOLID single strand and is what 

is known as Transformer Wire.  After wrapping the wire coils TIGHT you can use 

heat shrink tubing over them.  If you want to get fancy and I would; before 

you heat shrink tube them dip them in varnish.  They should be located close to 

the load device. 

Oh!  When choosing the wire size, do NOT go by the Mil-Spec wire size used in 

wiring the plane.  I would DOUBLE that wire size.



Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

nuckollsr(at)cox.net
Guest

Posted: Thu Aug 31, 2006 4:50 am Post subject: in-rush limiters

At 08:01 AM 8/31/2006 -0400, you wrote:

 	  Quote: 	

In a message dated 8/31/06 4:20:49 AM Eastern Daylight Time,

Erich_Weaver(at)URSCorp.com writes:

 > I am considering installing in-rush limiters for my landing  lights.  Can

 >  in-rush limiters be used effectively in conjunction with a wig-wag 

 flasher?

 >

 >  My understanding is that the in-rush limiters do their job through their

 >  odd property of providing decreasing resistance with increasing 

 heat.  That

 >  would imply that they would need time to cool down before being able to do

 >  their job the next time the power is turned on.  With the flasher however,

 >  the power is being turned on and off very quickly. On the other hand, the

 >  bulb filament is probably not cooling off a lot either between flashes, so

 >  maybe the in-rush limiters do not need to be effective when the wig-wag is

 >  wigging and wagging.

 >

 >  Did I just answer my own question? If so, can someone  recommend an

 >  appropriate in-rush limiter for my 12V, 75W halogen lights

 >

 >  thanks

 >

 >  Erich Weaver

===================================

Erich:

I am familiar with two types of inrush limiters.  Neither of them work off of

heat (I would like to learn more about this heat type).

   See

http://www.gesensing.com/products/resources/datasheets/cl.pdf

 	  Quote: 	
		  The simplest "limiter" you can build yourself.  It is nothing more than a

coil.  The coil can be made around either a dowel or a ferrite slug.  The 

wire

size is chosen to handle the current of the load and the basic size is about

1/2" ID, 1" OD and 2" Long.  The type of wire is SOLID single strand and 

is what

is known as Transformer Wire.  After wrapping the wire coils TIGHT you can 

use

heat shrink tubing over them.  If you want to get fancy and I would; before

you heat shrink tube them dip them in varnish.  They should be located 

close to

the load device.

   Adding inductance in series with a load does have an

   effect of softening an inrush current event. However,

   the time constant of an inductive circuit is (t=L/R)

   and the inductance of a 1" x 2" wood core inductor

   with 30T of wire on it is about 10 microhenries. Assuming

   one finds a suitable hunk of ferrite and assuming also

   a permeability of about 10, the inductance goes up to

   about 100 microhenries.  Cold closed loop resistance for

   a 75 watt lamp circuit will be on the order of 0.3 ohms yielding

   a max time constant on the order of .0001/0.3 or about 1/3

   millisecond for a ferrite core device. A wood core device

   yields about a 1/30 millisecond - rather short compared to the time

   constant of a part like the KC003L NTC current limiter that

   will be in the neighborhood of 10-100 milliseconds.

   An inductive current limiter would be so fast compared to

   the inrush time for a lamp filament as to offer little

   assistance in mitigating the magnitude of inrush current.

 	  Quote: 	
		  Oh!  When choosing the wire size, do NOT go by the Mil-Spec wire size used in

wiring the plane.  I would DOUBLE that wire size.

   Don't understand why. The current ratings for choosing wire

   size from charts like those found in AC43-13 or chapter

   8 of the 'Connection are already de-rated for 10C temperature

   rise.  The 6A lamp cited in the original post would not

   seriously warm an inductor wound with 22AWG (5A rated) wire.

   Bob . . .

Hopperdhh(at)aol.com
Guest

Posted: Thu Aug 31, 2006 3:51 pm Post subject: in-rush limiters

In a message dated 8/31/2006 8:53:53 A.M. Eastern Daylight Time,  nuckollsr(at)cox.net writes:

  	  Quote: 	
		     Don't understand why. The current ratings for choosing    wire

   size from charts like those found in AC43-13 or    chapter

   8 of the 'Connection are already de-rated for 10C    temperature

   rise.  The 6A lamp cited in the original post    would not

   seriously warm an inductor wound with 22AWG (5A    rated) wire.



   Bob . . .

	


 

 Bob,

  

 When wire is wound in a transformer or choke, the density of the power loss  is much greater than even in a bundle of wires.  A typical design value is  500 to 1000 circular mils per amp.  Solid number 22 wire is 25.3 mils  in diameter and has about 643 circular mils.  Therefore it is  only rated for about 1 amp when wound in a multi layered coil.  Operating a  number 22 enamel wire at 5 amps continuously when it is tightly surrounded by  more number 22 enamel wire also carrying 5 amps would cause it to  overheat.

  

 Dan Hopper

 Retired electrical engineer and transformer nut.

  

  

  [quote][b]

Hopperdhh(at)aol.com
Guest

Posted: Thu Aug 31, 2006 4:21 pm Post subject: in-rush limiters

Bob,

  

 Sorry, after rereading all the posts on this subject, I made a wrong  assumption in writing the reply below.  The reply still is correct, but  probably not applicable.

  

 Dan

  

  

 In a message dated 8/31/2006 7:54:57 P.M. Eastern Daylight Time,  Hopperdhh(at)aol.com writes:

  	  Quote: 	
		        In a message dated 8/31/2006 8:53:53 A.M. Eastern Daylight Time,    nuckollsr(at)cox.net writes:

    	  Quote: 	
		     Don't understand why. The current ratings for choosing      wire

   size from charts like those found in AC43-13 or      chapter

   8 of the 'Connection are already de-rated for 10C      temperature

   rise.  The 6A lamp cited in the original      post would not

   seriously warm an inductor wound with 22AWG      (5A rated) wire.



   Bob . . .

	


   

   Bob,

    

   When wire is wound in a transformer or choke, the density of the power    loss is much greater than even in a bundle of wires.  A typical design    value is 500 to 1000 circular mils per amp.  Solid number 22 wire is    25.3 mils in diameter and has about 643 circular mils.     Therefore it is only rated for about 1 amp when wound in a multi layered    coil.  Operating a number 22 enamel wire at 5 amps continuously when it    is tightly surrounded by more number 22 enamel wire also carrying 5 amps would    cause it to overheat.

    

   Dan Hopper

   Retired electrical engineer and transformer nut.

    

    

 	  Quote: 	
		  



matronics.com/Navigator?AeroElectric-List

.matronics.com/">http://forums.matronics.com

ronics.com/">http://wiki.matronics.com

://www.matronics.com/contribution">http://www.matronics.com/contribution



	
	


 

  

  [quote][b]

FLYaDIVE(at)aol.com
Guest

Posted: Fri Sep 01, 2006 3:58 am Post subject: in-rush limiters

 	  Quote: 	
		  Oh!  When choosing the wire size, do NOT go by the Mil-Spec wire size used in

wiring the plane.  I would DOUBLE that wire size.


	


   Don't understand why. The current ratings for choosing wire

   size from charts like those found in AC43-13 or chapter

   8 of the 'Connection are already de-rated for 10C temperature

   rise.  The 6A lamp cited in the original post would not

   seriously warm an inductor wound with 22AWG (5A rated) wire.



   Bob . . .

===================================

Hello Bob:



You have me smiling ...

Now how did I know you were going to question this part 



Let me start off by asking a LOADED QUESTION:



What determines the current handling capabilities of a wire?



I should wait at this point for a responce, but concidering that the question 

is also put the site's reading public ... I will guess at their answer and 

maybe yours.

That being:  The diameter, cross-sectional area of the wire.



Does that sound like the most given answer?  And it is a logical answer.  But 

not the whole story.  I did say it was a LOADED QUESTION.  



So to unload the answer:

The Determining factor is the INSULATION, the thickness and type.



Here is why.  You have to ask the questions: What fails? And How?

There are two failures.  As the wire heats up, it heats up so much that it 

MELTS the insulation.  FAILURE ... This exposes the wire to do any combination 

of events: Fire, short to ground - case - airframe or melt into and short to 

another wire.

The other failure is crystalization of the wire from the heat.  Usually 

repeated heat and that leads to the wire failing in an OPEN.  This is not the norm. 

 The norm is the insulation FAILING.

Now, most builders do use Mil-Spec wire and the Mil-Spec wire does have a 

higher tempature rating and dialectric rating.  So what determines the current 

handling capabilities of a wire? INSULATION - Told ya it was Loaded!



Lets switch to the coil construction I mentioned.  You said 30 Turns ... Only 

30 Turns?  Way Much More than 30 turns can fit on a form that has a 1/2" ID 

and a 1" OD and 2" Long ... That gives you 1/4" of room to build up and about 1 

1/4" length to fill.  I haven't worked out the Henry's (inductance) of the 

coil and quite honestly it does not matter.  Too much engineering and not enough 

practicality.  I know the size will work.  How do I know?  A life of 

experimentation!  I have been getting my ass shocked since I was 11 years old 

As the commercial says: Try it you'll like it.  As we say here in NJ: Don't 

worry about it!  

O!  For the size of the wire -- I would suggest 18 or 16 AWG enameled 

(Transformer) wire.  It should handle the current and both circuit heat and engine 

heat.  And even with this large size wire you should be able to get way more 

than 30 turns.

Try it you'll like it.  We are the EAA, Experiment!



Happy Toe Tingles.



Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

nuckollsr(at)cox.net
Guest

Posted: Fri Sep 01, 2006 4:06 am Post subject: in-rush limiters

At 07:50 PM 8/31/2006 -0400, you wrote:



 	  Quote: 	
		  In a message dated 8/31/2006 8:53:53 A.M. Eastern Daylight Time, 

nuckollsr(at)cox.net writes:

    Don't understand why. The current ratings for choosing wire

    size from charts like those found in AC43-13 or chapter

    8 of the 'Connection are already de-rated for 10C temperature

    rise.  The 6A lamp cited in the original post would not

    seriously warm an inductor wound with 22AWG (5A rated) wire.



    Bob . . .

Bob,



When wire is wound in a transformer or choke, the density of the power 

loss is much greater than even in a bundle of wires.  A typical design 

value is 500 to 1000 circular mils per amp.  Solid number 22 wire is 25.3 

mils in diameter and has about 643 circular mils.  Therefore it is only 

rated for about 1 amp when wound in a multi layered coil.  Operating a 

number 22 enamel wire at 5 amps continuously when it is tightly surrounded 

by more number 22 enamel wire also carrying 5 amps would cause it to overheat.


	


    Define "overheat". I'm aware of the transformer design

    philosophies but were talking about a single layer solenoid

    wound inductor.  The amount of current a 22AWG wire can carry

    without damaging its insulation is huge compared to the de-rating

    we impose for bundling and/or voltage drops.



    The 22AWG wire you see at:



http://www.aeroelectric.com/Pictures/Wire/20A_22AWG.jpg



    had been carrying 20A for several minutes at the time this

    picture was taken. The temperature as monitored by the

    thermocouple in the photo was still well below operating

    limits for the wire.



    One of the most difficult concepts to illuminate with

    respect to wires is that the recommended current RATINGS for

    wires are chosen for a suite of inter-related effects not

    the least of which is insulation type and ability of the

    wire to reject heat - as installed. The values cited in the

    wire bundle charts are not even close to being LIMITS beyond

    which one may expect smoke, fire and otherwise unhappy times

    in the cockpit.



    For the case cited (single layer inductor) the charted

    rating for 22AWG at 5A would be quite conservative even

    for the 6+ amp landing light cited . . . assuming that

    the inductive approach to inrush limiting was useful.



    Bob . . .

      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

FLYaDIVE(at)aol.com
Guest

Posted: Fri Sep 01, 2006 7:31 am Post subject: in-rush limiters

In a message dated 9/1/06 8:12:28 AM Eastern Daylight Time, nuckollsr(at)cox.net 

writes:



 	  Quote: 	
		   Define "overheat". I'm aware of the transformer design

      philosophies but were talking about a single layer solenoid

      wound inductor.  

===============================
	


Who said!



I said a form of 1/2" ID, 1" OD and 2" Long.  That is no single layer ... Not 

unless you are using 1/4" thick wire.



Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

nuckollsr(at)cox.net
Guest

Posted: Mon Sep 04, 2006 5:13 am Post subject: in-rush limiters

At 07:56 AM 9/1/2006 -0400, you wrote:



 	  Quote: 	
		  



 >Oh!  When choosing the wire size, do NOT go by the Mil-Spec wire size 

 used in

 >wiring the plane.  I would DOUBLE that wire size.



    Don't understand why. The current ratings for choosing wire

    size from charts like those found in AC43-13 or chapter

    8 of the 'Connection are already de-rated for 10C temperature

    rise.  The 6A lamp cited in the original post would not

    seriously warm an inductor wound with 22AWG (5A rated) wire.



    Bob . . .

===================================

Hello Bob:



You have me smiling ...

Now how did I know you were going to question this part 



Let me start off by asking a LOADED QUESTION:



What determines the current handling capabilities of a wire?



I should wait at this point for a responce, but concidering that the question

is also put the site's reading public ... I will guess at their answer and

maybe yours.


	




 	  Quote: 	
		  That being:  The diameter, cross-sectional area of the wire.



Does that sound like the most given answer?  And it is a logical answer.  But

not the whole story.  I did say it was a LOADED QUESTION.



So to unload the answer:

The Determining factor is the INSULATION, the thickness and type.


	


    Sure. Cross section controls resistance, but says nothing

    about ability to reject heat energy due to I(squared)R heating

    combined heat transfer physics of the assembly.

 	  Quote: 	
		  Here is why.  You have to ask the questions: What fails? And How?

There are two failures.  As the wire heats up, it heats up so much that it

MELTS the insulation.  FAILURE ... This exposes the wire to do any 

combination

of events: Fire, short to ground - case - airframe or melt into and short to

another wire.


	


    Yup.



 	  Quote: 	
		  The other failure is crystalization of the wire from the heat.  Usually

repeated heat and that leads to the wire failing in an OPEN.  This is not 

the norm.

  The norm is the insulation FAILING.


	


   Temperature rises that put COPPER at risk are so much

   beyond temperatures that damage insulation that failure

   of the conductor is exceedingly low on the list of concerns.



 	  Quote: 	
		  Now, most builders do use Mil-Spec wire and the Mil-Spec wire does have a

higher tempature rating and dialectric rating.  So what determines the 

current

handling capabilities of a wire? INSULATION - Told ya it was Loaded!


	


    Yup, this is discussed in Chapter 8.



 	  Quote: 	
		  Lets switch to the coil construction I mentioned.  You said 30 Turns ... Only

30 Turns?  Way Much More than 30 turns can fit on a form that has a 1/2" ID

and a 1" OD and 2" Long ... That gives you 1/4" of room to build up and 

about 1

1/4" length to fill.  I haven't worked out the Henry's (inductance) of the

coil and quite honestly it does not matter.  Too much engineering and not 

enough

practicality.  I know the size will work.


	


   Define "work". The goal is to add a SIGNIFICANT reduction in area under the

   inrush current curve without degrading system performance. I guess I don't

   know about "too much engineering" . . . it's been said that if the only tool

   you have is a hammer, lots of things begin to look more and more like a 

nail.

   I'm an engineer and my first thoughts for working a problem DO focus on

   the physics.



 	  Quote: 	
		     How do I know?  A life of

experimentation!  I have been getting my ass shocked since I was 11 years 

old 

As the commercial says: Try it you'll like it.  As we say here in NJ: Don't

worry about it!


	


   Whether one chooses to worry or not to worry, the physics

   doesn't change.

 	  Quote: 	
		  O!  For the size of the wire -- I would suggest 18 or 16 AWG enameled

(Transformer) wire.  It should handle the current and both circuit heat 

and engine

heat.  And even with this large size wire you should be able to get way more

than 30 turns.


	


   Inrush Limiting 101



   Agreed. Taking your adjustments to my mis-perceptions of the

   hypothesized single layer coil, let us assume as follows:



   1/2" od core 2" long wound with 5 layers of #16AWG wire

   (0.050" diameter) for a depth on the order of .25" for a total

   diameter of 1". 050" wire will take 40T to cover 2" of

   length for each layer so 5 layers is 200T total.



   Goto:



http://www.captain.at/electronics/coils/

   . . . and plug in 200T, 1" and .5" and 2" (be sure to select

   units to "inches" and we get about 300 microhenries. Assuming a

   ferrite core with permeability of 10, we might push this inductance up

   to 3 millihenries.



   Let us further consider 16AWG wire with a resistance of about 4 milliohms

   per foot.  The 200T will have an average circumference of .75 x 3.14 or

   or 2.3 inches. 200T offers a total length of 460 inches or 38 feet

   and a resistance of 150 milliohms.



 	  Quote: 	
		  Try it you'll like it.  We are the EAA, Experiment!


	


    Good idea. Went to the bench and measured the cold-resistance

    of a 65W, halogen head lamp bulb and got 0.150 ohms. 12v applied

    directly to the terminals of this lamp will produce an in-rush

    current of 12.0 /0.15 = 80 Amps! Okay, lets wire it up with some

    clip leads and a 12v battery and plot this puppy. Here we get

    a curve like . . .



http://www.aeroelectric.com/Pictures/Curves/Exemplar_Incandescent_Lamp_Inrush.gif



    Note that the peak inrush current was not 80 amps, but just

    about 38 amps. Okay, this means that circuit cold-resistance

    was 12/38 or 315 milliohms. Understandable. Wire used to hook

    the system up combined with about 15 milliohms of battery

    resistance produces a new, higher cold-resistance.



    Adding your hypothesized inductor of 3 millihenries and

    150 milliohms would raise the total circuit cold resistance to

    315 + 150 = 460 milliohms. Adding the inductor would produce

    a drop in in-rush current to about 26 amps if it exhibited

    no inductive characteristics at all!



    Going back to the curve we see that the time constant (measured

    to 37% of the delta between peak (38A) and static (5A) or

    (38-5)*.37 + 5 = 17A. The trace crosses 17A at about 15

    milliseconds. At this same time, total loop resistance is on the

    order of 600 milliohms without the hypothesized inductor.



    I do not doubt that you observed reductions in in-rush

    current as a byproduct of the actions you suggested.

    It's easy to see here that adding the hypothesized inductor

    will indeed cause a significant drop in the inrush current,

    NOT because it's an inductor, but because it adds a

    significant resistance to the circuit. The L/R time constant

    for the added inductance is still much shorter than the

    15 millisecond time constant demonstrated on the bench

    so that the benefits of adding the inductance are small

    at best.



    Inrush Limiting 102



    If inrush limiting is a really big thing for the designer,

    there are thermal devices offered by a several manufacturers.

    Here's one example:



http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/GE_Sensors/CL_limiters.pdf



    In this case, we're adding to the cold-resistance of the

    circuit by means of a style of thermistor . . . a temperature

    sensitive resistor chosen for its NEGATIVE temperature

    characteristics. The hotter it gets, the lower the resistance.



    Take a look at p/n CL-30. It has a cold-resistance on the order

    of 2.5 ohms. Adding this resistance in series with the

    hypothetical .315 ohms cited above raises the cold-resistance

    of the system to about 2.8 ohms. This will reduce the in-rush

    current observed to 12 / 2.8 = 4.3 amps! Nice reduction indeed.

    Now, as the thermistor is allowed to heat up, we see that

    when loaded to 50% of rated load (It's a an 8A device and

    our 55w lamp will load it to about 4A) its operating resistance

    drops to about 140 milliohms.  The power tossed off under

    normal operating conditions is .14 x 4 = .56 volts x 4A =

    2.25 Watts. This is about the same losses as for the

    hypothesized inductor cited above but with a profound

    effect on in-rush current.



    Caveats:  The CL-30 inrush limiter must be allowed to heat

    up. One cannot clamp it down against a heat-sinking surface

    for mechanical support lest you soak the heat energy out.

    This can cause excessive dissipation internal to the device

    and failure (been there, done that).  On the other hand,

    the critter is mounted on 18AWG solid copper leads and

    not terribly resistant to breakage under vibration. On

    the GP-180 program we wrapped the limiter in fiberglas

    tubing before capturing it under an aluminum bracket.



    In the final analysis, builder needs to decide what return

    on investment is needed on an effort to mitigate in-rush.

    The original goal was to increase lamp life. In the BH

    era (before halogen) there was some benefit to lamp life

    by considering some form of keep warm or inrush limiting.

    Nowadays, I doubt that the return on investment is

    positive. The bulbs are very long lived running "barefoot"

    but they're still going to fail at some point in time -

    in-rush limiting is not a reliability issue.



    So unless your system is vulnerable to the effects of

    a 40 amp, 20 millisecond transient (shame on you if it

    is!), then there's no positive return on investment I

    can perceived for adding special in-rush limiting

    features to your landing light system.



    Bob . . .

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