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Contactor and Crowbar Ratings

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ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Thu May 14, 2009 6:06 am Post subject: Contactor and Crowbar Ratings

Bob:



I looked at the contactors made by Eaton that are 337 approved for Cessna Aircraft.  Eaton P/N PW6041H215.  rated for 28 volts continuous which is good for my 24 volt experimental aircraft.  My question is about the crowbar circuit for overvoltage protection of the ground relay.  The ones I see B&C and aeroelectric carry are rated at 12 VDC and 24 VDC.  Shouldn't they be 15 VDC and 28 VDC to allow for battery charging thru the ground power port?  If so, can the ones you sell be modified for this?



Craig

nuckolls.bob(at)aeroelect
Guest

Posted: Thu May 14, 2009 6:35 am Post subject: Contactor and Crowbar Ratings

At 09:06 AM 5/14/2009, you wrote:

 	  Quote: 	
		  

<capav8r(at)gmail.com>



Bob:



I looked at the contactors made by Eaton that are 337 approved for 

Cessna Aircraft.  Eaton P/N PW6041H215.


	


   When you can find these, get a grip on your

   wallet. While these are the cream of the crop

   for DC contactors, they're quite pricey.



 	  Quote: 	
		    . . .  rated for 28 volts continuous which is good for my 24 volt 

 experimental aircraft.  My question is about the crowbar circuit 

 for overvoltage protection of the ground relay.  The ones I see B&C 

 and aeroelectric carry are rated at 12 VDC and 24 VDC.  Shouldn't 

 they be 15 VDC and 28 VDC to allow for battery charging thru the 

 ground power port?  If so, can the ones you sell be modified for this?


	


   No, generally speaking 12/14 and 24/28 are

   interchangeable with respect to functionality.

   The low-cost 12/24v RBM/Stancore/W-R and Cole-Hersee

   battery contactors offered by B&C and others

   are quite suited to our task.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Thu May 14, 2009 5:53 pm Post subject: Re: Contactor and Crowbar Ratings

Bob:



Spoke with Bill at B&C.  Their 24 volt crowbar trips at 32 VDC.  That is OK.  



However, I am having difficulty finding a contactor for a 24 VDC application.  The Stancor ones have a coil voltage of 24 VDC or 36 VDC.  However, 28 VDC exceeds the coil voltage of the 24 VDC unit so it can't work.  Also, their 36 VDC contactors will not work because of the coil voltage being too high to activate it.  Bottom line is I need a contactor with a coil voltage rating of 28 VDC.  Other than the Eaton unit (which you are correct is costly) I am running out of luck.  Any ideas?



Craig

nuckolls.bob(at)aeroelect
Guest

Posted: Thu May 14, 2009 7:21 pm Post subject: Contactor and Crowbar Ratings

At 08:53 PM 5/14/2009, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Craig Winkelmann" <capav8r(at)gmail.com>



 Bob:



 Spoke with Bill at B&C.  Their 24 volt crowbar trips at 32 VDC.  That is OK.  	


    Yes . . . the nominal trip range for 14v ov protection

    is 16.2 to 16.5 volts. 28v aircraft it's 32.4 to 33 volts.



  	  Quote: 	
		  However, I am having difficulty finding a contactor for a 24 VDC application.  The Stancor ones have a coil voltage of 24 VDC or 36 VDC.  However, 28 VDC exceeds the coil voltage of the 24 VDC unit so it can't work.  Also, their 36 VDC contactors will not work because of the coil voltage being too high to activate it.  Bottom line is I need a contactor with a coil voltage rating of 28 VDC.  Other than the Eaton unit (which you are correct is costly) I am running out of luck.  Any ideas? 	


    I can tell you that the 70 series, continuous duty contactors

    have been used in 14 and 28 volt aircraft with good

    service histories. Yes, they run warm. But in airplanes,

    the ambient temperatures for most operating conditions

    are lower that max rated for 12v operation which tends

    to offset the effects of the extra heating.



    The 70-903 contactor has a resistance of 60 ohms

    operating at room temperature. If you're worried

    about it, you could put a 6 ohm, 1W resistor in

    series with the coil to "cool" it off by about

    10% of applied voltage . . . but I think you're

    okay without it. These contactors have been around

    since about WWII. While they're not "Space Rated"

    contactors, they've proven to be of good value

    in a failure tolerant airplane. 



    Even the $high$ contactors have bad days



  http://tinyurl.com/qmk6gm 



    If you're loosing sleep over it, consider the

    these EV200 series contactors. They feature

    automatic coil current reduction after pull-in

    to reduce continuous power to keep the contactor

    energized. However, they're about 6X the price

    of the 70 series device and do generate some

    noise that has been a problem for a few builders.

    See:



  http://tinyurl.com/qazl8t

  



 

 

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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



     [quote][b]

Bob McC

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

Posted: Thu May 14, 2009 7:35 pm Post subject: Contactor and Crowbar Ratings

As Bob N stated in his earlier reply 24 and 28 volt components are

interchangeable. (They are the same thing from a practical/functional point

of view) just as 12 and 14 volt components are. Items such as contactors,

relays, motors, light bulbs etc are just not that voltage sensitive that

they are affected by the normal swing of system voltages. Your 24 volt

(nominal) system may experience actual measured voltages from a low of say

20 (maybe less) to a high of 28, 29 (maybe more) but all of the nominally

rated 24 volt components will function just fine. It's like your house

current at home. It may be 110,112, 115,120,125, 130 Volts or thereabouts if

you actually measure it, but you don't use different toasters, washing

machines, light switches etc for these different values. Standard 120 volt

rated devices are close enough. Similarly 24 volt devices are fine for any

voltage likely to be present in a 24 /28 volt aircraft. 



Another Bob

Bob McC



[quote] --

_________________
Bob McC
Falco #908
(just starting)

ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Fri May 15, 2009 6:18 am Post subject: Re: Contactor and Crowbar Ratings

Thanks for the reply.  When looking at the Stancor 70-903 data sheet it states the Max Safe Operating Range is 110% of nominal rated voltage.  That gives me 26.4 volts.  In a 24 volt system, the bus voltage often runs near 28 volts for the alternator to charge the battery.  That is over the rating.



Additionally, in the Stancor documentation for sizing a contactor, they specifically state a warning about using contactors rated at battery voltage when there is charging taking place.  For 12 VDC systems, they make a 15 VDC contactor but have no such beast for a 24 vdc system.



Also, Bob, take a look at the URLs in your last post.  Some malware or something has changed the url to some odd url.



Craig

ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Fri May 15, 2009 8:35 am Post subject: Re: Contactor and Crowbar Ratings

OK, after much research, the Gigavac GX11CA it is.  I spoke with one of their engineers and it is designed for 28 VDC continuous use.  In addition, it is hermetically sealed as an added plus and it has built in spike suppression so it needs no external diodes.  There are also models that have an extra contact for switching on an indicator light if wanted.  Price is $113 each.  So, more that Stancor, less than Kilovac and much less than CH.



Thanks for all your help and direction!



Craig

nuckolls.bob(at)aeroelect
Guest

Posted: Fri May 15, 2009 10:38 am Post subject: Contactor and Crowbar Ratings

Thanks for the reply.  When looking at the Stancor 70-903 data

sheet it states the Max Safe Operating Range is 110% of

nominal rated voltage.  That gives me 26.4 volts.  In a 24 volt

system, the bus voltage often runs near 28 volts for the alternator

to charge the battery.



    Actually 28.5 volts nominal . . .



That is over the rating.



Additionally, in the Stancor documentation for sizing a contactor, 

they specifically state a warning about using contactors rated at 

battery voltage when there is charging taking place.  For 12 VDC 

systems, they make a 15 VDC contactor but have no such beast for a 24 

vdc system.



   I've read the warning and I've observed the performance

   of these contactors in service since they went into the

   C-140 back in '46 or so. B&C and I have sold hundreds of

   these critters for the purpose of providing battery

   contactor, external power and cross-feed service for

   many moons . . . and found that they continue to offer

   satisfactory service in these applications. But if this

   idea stresses your sensibilities too much, there ARE

   several alternatives . . .



   One COULD also craft a after-pull-in power reduction

   module to emulate the performance of devices like

   the EV200. A 555 timer and a few jelly-beans would

   probably make it work.



Also, Bob, take a look at the URLs in your last post.  Some malware 

or something has changed the url to some odd url.



   Looked over my postings as they arrived here

   and didn't see anything out of the ordinary.

   Which URL you saw was hosed?



        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Sun May 17, 2009 1:42 pm Post subject: Re: Contactor and Crowbar Ratings

Bob:



These urls



Even the $high$ contactors have bad days 



http://tinyurl.com/qmk6gm 



If you're loosing sleep over it, consider the 

these EV200 series contactors. They feature 

automatic coil current reduction after pull-in 

to reduce continuous power to keep the contactor 

energized. However, they're about 6X the price 

of the 70 series device and do generate some 

noise that has been a problem for a few builders. 

See: 



http://tinyurl.com/qazl8t 

 	  Quote:

nuckolls.bob(at)aeroelect
Guest

Posted: Sun May 17, 2009 6:03 pm Post subject: Contactor and Crowbar Ratings

At 04:42 PM 5/17/2009, you wrote:




Bob:



These urls



Even the $high$ contactors have bad days



http://tinyurl.com/qmk6gm



    . . . and this 6041 series contactor . . .

    in spite of its pedigree had a very

    bad day in a King Air about 20 years

    ago.

If you're loosing sleep over it, consider the

these EV200 series contactors. They feature

automatic coil current reduction after pull-in

to reduce continuous power to keep the contactor

energized. However, they're about 6X the price

of the 70 series device and do generate some

noise that has been a problem for a few builders.

See:



http://tinyurl.com/qazl8t



    . . . and this is an exemplar 21st century

    design for a contactor along with a place to

    purchase the critter.



    These are "Tiny URL" contractions of the

    desired address. See:



http://tinyurl.com

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

Bob McC

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

Posted: Sun May 17, 2009 6:36 pm Post subject: Contactor and Crowbar Ratings

Craig;



Both those URL's work fine for me.



Bob McC

Do not archive



[quote] --

_________________
Bob McC
Falco #908
(just starting)

jquinn3(at)gmail.com
Guest

Posted: Tue May 19, 2009 12:38 am Post subject: Contactor and Crowbar Ratings

Bob,Why would the Tyco EV200 create noise in some applications and how could this problem be mitigated?



On Sun, May 17, 2009 at 16:42, Craig Winkelmann <capav8r(at)gmail.com (capav8r(at)gmail.com)> wrote:

 [quote]--> AeroElectric-List message posted by: "Craig Winkelmann" <capav8r(at)gmail.com (capav8r(at)gmail.com)>

  

 Bob:

 

 These urls

 

 Even the $high$ contactors have bad days

 

 http://tinyurl.com/qmk6gm

 

 If you're loosing sleep over it, consider the

 these EV200 series contactors. They feature

 automatic coil current reduction after pull-in

 to reduce continuous power to keep the contactor

 energized. However, they're about 6X the price

 of the 70 series device and do generate some

 noise that has been a problem for a few builders.

 See:

 

 http://tinyurl.com/qazl8t

 

 >

 

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=244422#244422

 

 

 

 

 

 

 

 ===========

 -List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

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

 ===========

 

 

 

 [b]

nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 19, 2009 4:41 am Post subject: Contactor and Crowbar Ratings

At 03:33 AM 5/19/2009, you wrote:

 	  Quote: 	
		  Bob,

Why would the Tyco EV200 create noise in some applications and how 

could this problem be mitigated?


	


    "Noise" by definition is the artifact of rapidly

    changing current flow that propagates from some

    antagonist to some victim. This is described in

    more detail in the book. Sometimes the 'noise'

    is an intentional byproduct of a useful radiation.

    For example, you radiate strong signals from your

    comm and transponder antennas to achieve

    a useful purpose. In some cases, the stronger the

    radiation, the better. However, this radio frequency

    energy can become a nuisance too. Its sorta like

    being pleased that your wheat fields are benefiting

    from a good rain shower but the holes in your roof

    are a source of concern.



    The EV200 (and similar devices) use an transistor

    that's turned on with varying duty cycle to reduce

    current in the contactor coil after pull-in is

    achieved. The speed of the switching device, the

    amount of current it carries, the area of its

    "antennas", the frequency of operation and the

    artifacts of current modulation flowing out on

    the wires are all ingredients that go into

    a recipe for problems.



    The stuff that gets outside the product needs

    to be evaluated for potential nuisance if not

    hazard.  This is part of what DO-160/Mil-STD-704

    is about. In the case of the EV200, the occasional

    OBAM aircraft builder has heard the duty cycle

    switching of the EV200's control electronics as

    a "buzz" in their audio system.



    I've not been able to put my hands on one of these

    problems to deduce the magnitude of potential noise

    or track down the specific propagation path. However,

    it's a pretty fair bet that poor grounding techniques

    are the probable cause.



    I wouldn't shy away from an EV200 installation

    based on a reported noise issue. I've never found

    a noise problem I couldn't fix. I've found problems

    that the customer decided not to fix because it

    involved $millions$ of design changes to an

    airframe. But in our airplanes, the risk of noise

    is low, the cost of the solution is not great.



    In response to our List discussion late last week

    on the ratings for the lowly el-cheeso contactors,

    I've begun a design for a contactor power management

    module. This device will be assembled much like the

    over voltage modules . . . quasi-potted in double

    walled heat shrink. It's easy to add this device

    to an el-cheeso contactor and achieve improved

    electrical performance that emulates the EV200.



    At the same time, it separates control electronics

    from the contactor. If the contactor ever requires

    replacing, then you don't need to buy new electronics.

    Similarly, if the electronics craps, you don't toss

    out a perfectly good contactor. See:



http://www.aeroelectric.com/Catalog/AEC/9024/9024-700-1P1.pdf



    I have an upcoming opportunity to get into the EMC

    lab with a customer's product for DO-160 conducted

    emissions testing. I'm planning to piggy-back a

    couple of my projects into the same testing session.

    If my software guru can get me some exemplar chips

    for the 9024, I can do an EMC look-see to confirm

    my confidence in its OBAM aircraft friendly demeanor.



    This module will drastically reduce the temperature

    rise on the RBM/W-R/Stancore contactors. This not only

    reduces energy required to keep the critter closed,

    it honors the manufacturer's ratings limits for

    use in systems with bus voltages high enough to

    charge batteries.



        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

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