Re: RE- Varistors (was Info and requests for book)

• To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
• Subject: Re: RE- Varistors (was Info and requests for book)
• From: Tesla List <tesla-at-stic-dot-net>
• Date: Fri, 19 Sep 1997 09:29:13 -0500
• Approved: tesla-at-stic-dot-net

From: 	David Sharpe[SMTP:sccr4us-at-erols-dot-com]
Reply To: 	sccr4us-at-erols-dot-com
Sent: 	Friday, September 19, 1997 5:55 AM
To: 	Tesla List
Subject: 	Re: RE- Varistors (was Info and requests for book)

Tesla List wrote:
> 
> From:   Robert Michaels[SMTP:robert.michaels-at-online.sme-dot-org]
> Sent:   Thursday, September 18, 1997 4:50 PM
> To:     tesla-at-pupman-dot-com
> Subject:        RE- Varistors (was Info and requests for book)
> 
>         Take note.  Varistors are vaguely like fuses.  They are
>         not designed to function repeatedly.
> 
----------------------
<<SNIP, SNIP>>
	
Robert, ALL

I've used varistors for 20+ years in industrial electronics.
Several notes of importance:

1. Robert's previous comment about varistors degrading with
   use is correct, Harris Semiconductor doesn't like to 
   admit to it, but I've noticed loss of performance with use.
2. NOTE TO LIST, WHEN VARISTORS FAIL <<AND THEY WILL!!!>> THEY 
   FAIL SHORTED!!! I SPEAK FROM EXPERIENCE ON THIS ONE. Notice
   that when they are used, they are usually on the load side 
   of some kind of overcurrent protection (fuses or CB's).
3. Never soldier into a circuit without heatsinking, the soldiering
   process heats the die, and shifts the varistor clamp voltage
   LOWER.  You'll know somethings wrong when you plug in your
   equipment (hint:  ZZZAAAPPPPP_BOOOOM!!!)

Regards

DAVE SHARPE, TCBOR

	

Rober

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