[TenTec] Airpax Breaker Part and Source

[art davis]

I'm no expert, BUT...

be very careful with the use of the term "instant trip" when referring to a circuit breaker or fuse. All circuit protection devices take a finite amount of time to operate, no matter what type they happen to be. Look at the response curves (i.e. trip curves) for any breaker or fuse and you'll see that it may be very quick indeed (less than a millisecond in many cases) if the fault current is high enough, but not "instant". And in the world of semiconductors very quick might not be fast enough. And look at the curves to see the level of current that can flow through the device without it tripping at all. You might be surprised.  I may be wrong but I doubt that there is any circuit breaker on the market that, when located upstream at the power supply, can operate fast enough to protect semiconductors from damage due strictly to overcurrent. If the fault current is high enough (many times the circuit breaker rating) they may offer some limited protection from the heat generated by the overcurrent flowing through the device, but the semiconductor itself must be capable of surviving the current in the first place. 

The primary reason to specify different response time characteristics (trip curves) for circuit breakers (slow blow, fast, etc...) is to make sure that the power feeder circuit maintains proper trip coordination among the various circuit protection devices in the circuit in case of a fault in the wiring upstream of the load. In most power distribution systems the fuses and circuit breakers upstream of an end user (i.e. radio) are there only to protect the wiring between the power source and the load. The load (in this case, the radio) must protect itself internally.  My guess is that there could be significant damage done inside a transceiver long before a 20A breaker all the way back at the power supply knew what was happening. 

Of course, the flip side to all this is that it couldn't hurt, right? You certainly won't have any protection if you don't use something, so put the fastest breaker in there that you can find  and keep your fingers crossed! Just don't call it "instant"

Art, N4UC

> Date: Mon, 13 Dec 2010 20:54:08 -0500
> From: wb2vuf at verizon.net
> To: tentec at contesting.com
> CC: rhulett1 at consolidated.net
> Subject: Re: [TenTec] Airpax Breaker Part and Source
> 
> Curt:
> 
> Most Ten Tec owners seem to be going to Poco Sales  
> (http://www.pocosales.com/). They have a minimum order of $25. The 
> breaker that you have looks like the Ten Tec 1140, which was used for 
> the Corsair and similar rigs. The "0" after the T11 indicates an instant 
> trip breaker, which, according to Poco, is very scarce. I exchanged some 
> e-mail correspondence with them  about a week ago.  Here is what they 
> quoted:
> 
> "The 20A quoted below has been put to use in hundreds of Ten-Tec 
> applications and none have yet to complain."
> T11-1-20.0A-01-11C-V    @ $12.50/ea
> Parts are in stock
> 
> They know about the 17.5 amp instant trip requirement, but they do not 
> stock such a breaker.
> 
>   I  am looking for a fast trip 5 amp breaker for my Century 22, but 
> that is not a stock item, either (8 weeks lead time).  They do stock 
> slow trip breakers but I don't think they are  fast enough to protect 
> the finals, which is why Ten Tec specified instant or fast trip breakers.
> 
> If you only need one breaker, you can probably team up with a couple of 
> other guys to make the minimum order.
> 
> 
>                              73,
> 
>                              Bob WB2VUF
> 
> On 12/13/2010 9:31 AM, Curt wrote:
> > I'm looking for best part number and source for an Airpax magnetic breaker
> > for less than 18A.  I think the correct number is T11-0-17.5A-01-10A-V.
> > Appreciate any advice about this.
> >
> > 73, Curt KB5JO
> >
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