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AeroElectric-List Digest: 11 Msgs - 09/12/08

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bmwr606(at)yahoo.com
Guest

Posted: Sat Sep 13, 2008 7:51 am Post subject: AeroElectric-List Digest: 11 Msgs - 09/12/08

Vern, 



you quoted Carling switch ratings, but if you read further down on the page, you find the following:



 "Types of Loads:

 An electric load is the

amount of electric power delivered or required at any specific point or

points on a system. The requirement originates at the energy consuming

equipment of the consumers. More simply put, a load is the piece of

equipment you turn on and off. 

Resistive loads primarily offer resistance to the flow

of current. Examples of resistive loads include electric heaters,

ranges, ovens, toasters, and irons. If the device is supposed to get

hot and doesn't move, it's most likely a resistive load.

Inductive loads are usually devices that move and

normally include electric magnets, like an electric motor. Examples of

inductive loads include such things as power drills, electric mixers,

fans, sewing machines, and vacuum cleaners. Transformers also produce

inductive loads.

High Inrush loads draw a higher amount of current or

amperage when first turned on, compared to the amount of current

required to continue running. An example of a high inrush load is a

light bulb, which may draw 20 or more times its normal operating

current when first turned on. This is often referred to as lamp load.

Other examples of loads that have high inrush are switching power

supplies (capacitive load) and motors (inductive load).

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retasker(at)optonline.net
Guest

Posted: Sat Sep 13, 2008 9:00 am Post subject: AeroElectric-List Digest: 11 Msgs - 09/12/08

A comment on the below comments:



If you look at the schematic Vern posted, you would see that he is using 

NTC surge limiters on each light.  These minimize startup surges caused 

by the very low cold filament resistance of the lamps.



On the other hand, it depends on the time constants of the NTC surge 

limiters vs the time constants of the lamp filaments as to whether these 

are effective when in wig-wag mode.



Dick Tasker



Scott Klemptner wrote:

[quote] Vern,



 you quoted Carling switch ratings, but if you read further down on the 

 page, you find the following:

  

 "Types of Loads:

  An *electric load* is the amount of electric power delivered or 

 required at any specific point or points on a system. The requirement 

 originates at the energy consuming equipment of the consumers. More 

 simply put, a load is the piece of equipment you turn on and off.



 *Resistive loads* primarily offer resistance to the flow of current. 

 Examples of resistive loads include electric heaters, ranges, ovens, 

 toasters, and irons. If the device is supposed to get hot and doesn't 

 move, it's most likely a resistive load.



 *Inductive loads* are usually devices that move and normally include 

 electric magnets, like an electric motor. Examples of inductive loads 

 include such things as power drills, electric mixers, fans, sewing 

 machines, and vacuum cleaners. Transformers also produce inductive loads.



 *High Inrush loads* draw a higher amount of current or amperage when 

 first turned on, compared to the amount of current required to 

 continue running. An example of a high inrush load is a light bulb, 

 which may draw 20 or more times its normal operating current when 

 first turned on. This is often referred to as lamp load. Other 

 examples of loads that have high inrush are switching power supplies 

 (capacitive load) and motors (inductive load).



 .



 .



 .



 .



 .



 L & T Ratings



  An "L" rating denotes the ability of a switch to handle the initial 

 high inrush characteristics of a Tungsten Filament Lamp on AC voltage 

 only. A "T" rating is the equivalent lamp load for DC.

   H Rating



 An "H" rating denotes a non-inductive resistive rating. Ratings listed 

 in Carling Technologies' product information may appear with the 

 symbol "H" or with the words "non-inductive" or "resistive". "H" 

 ratings are typically required for switches used in commercial oven 

 applications."



 Are you sure you are using the switches within their rated 

 specs???????????



 My experience using AC rated switches on DC circuits with high inrush 

 currents (landing/taxi lights and strobes in particular) is failure 

 after failure.



 Eric....this includes ROCKER SWITCHES TOO!.... Cessna rocker switches 

 used in the 70's for example (AC rated "Mr Coffee Maker switches).



 My $.02 worth......



 Scott A Klemptner

 bmwr606 on Yahoo IM



 What if the Hokey-Pokey IS what it's all about?



 ---

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mrspudandcompany(at)veriz
Guest

Posted: Sat Sep 13, 2008 9:30 am Post subject: AeroElectric-List Digest: 11 Msgs - 09/12/08

Vern, 



you quoted Carling switch ratings, but if you read further down on the page,

you find the following:



 



"Types of Loads:

 An electric load is the amount of electric power delivered or required at

any specific point or points on a system. The requirement originates at the

energy consuming equipment of the consumers. More simply put, a load is the

piece of equipment you turn on and off. 



Resistive loads primarily offer resistance to the flow of current. Examples

of resistive loads include electric heaters, ranges, ovens, toasters, and

irons. If the device is supposed to get hot and doesn't move, it's most

likely a resistive load.



Inductive loads are usually devices that move and normally include electric

magnets, like an electric motor. Examples of inductive loads include such

things as power drills, electric mixers, fans, sewing machines, and vacuum

cleaners. Transformers also produce inductive loads.



High Inrush loads draw a higher amount of current or amperage when first

turned on, compared to the amount of current required to continue running.

An example of a high inrush load is a light bulb, which may draw 20 or more

times its normal operating current when first turned on. This is often

referred to as lamp load. Other examples of loads that have high inrush are

switching power supplies (capacitive load) and motors (inductive load).

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rv-9a-online(at)telus.net
Guest

Posted: Sat Sep 13, 2008 9:39 am Post subject: AeroElectric-List Digest: 11 Msgs - 09/12/08

Hi Scott.  The landing and taxi light circuits have inrush current limiters

installed, for this very reason.  The objective was to save wear and tear on

the switches.  Steady state draw is about 5 amps.

As for the strobe supply, there was some debate on my theory of why this is

the worst load in the a/c.  My hypothesis is that strobe supplies have a

negative voltage-current relationship (negative resistance).  If you reduce

the voltage to a strobe supply (or, in fact many switchmode power supplies),

its current actually increases.  Once a switch or terminal fails, this leads

to thermal runaway and the results are what I have seen (twice).  

 

Not everyone agrees, but I've had this failure twice and Bob has documented

another one-- all in the strobe circuits. 

 

Thanks for your feedback.



--

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