[GreenKeys] Loop supply rheostats Watt Rating?

[Peter Gottlieb]

As a design engineer, it is considered. 


Peter

> On Sep 13, 2019, at 12:17 AM, hwhall at compuserve.com wrote:
> 
> I do not disagree; it makes sense.  Excessive current is a factor to be considered.  And, of course, increasing current increases power dissipated to heat by the square of the increase.  And too much heat is what converts resistance wire into light & smoke.  :-)
> 
> It seems worth observing that in my experience (I bet others, too) resistors, including variables, are far more often found with watt ratings stamped on them than with max current stamped on them. Apparently, max current data may be in the manufacturer's datasheets but we probably don't often seek it out.  <shrug>
> 
> Wayne
> WB4OGM
> 
> -----Original Message-----
> From: Jeffrey Angus <jdangus at att.net>
> To: greenkeys <greenkeys at mailman.qth.net>
> Sent: Thu, Sep 12, 2019 9:55 pm
> Subject: Re: [GreenKeys] Loop supply rheostats Watt Rating?
> 
> On 9/12/19 10:41 PM, hwhall at compuserve.com wrote:
>> If we only used half the resistance windings, the entire unit's mass
>> & area is still there as a heat sink/radiator.
>> 
> But that's not how variable resistors are rated.
> The rating is maximum current. Period.
> If you exceed the maximum current rating, you risk watching
> your rheostat turn into a very expensive fuse.
> 
> 
> -- 
> "I am a river to my people."
> Jeff-1.0
> WA6FWI
> www.foxsmercantile.com
> 
> 
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