Re: Variac Wiring

• To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
• Subject: Re: Variac Wiring
• From: Tesla List <tesla-at-stic-dot-net>
• Date: Mon, 8 Dec 1997 20:29:37 -0600
• Approved: tesla-at-stic-dot-net

From: 	Gary Lau  08-Dec-1997 0927[SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent: 	Monday, December 08, 1997 7:42 AM
To: 	tesla-at-pupman-dot-com
Cc: 	absmith-at-tiac-dot-net
Subject: 	Re: Variac Wiring

>From: 	Adam[SMTP:absmith-at-tiac-dot-net]
>
>I had to take apart my variac (Powerstat 116, 120V 7.5A 1PH) today to 
>replace the switch, and when I removed the housing, I found two 
>unconnected terminals numbered 4 & 5.  The schematics seem to be like 
>this:
>
>      ____ 1
>     (
>5 ___(
>     (
>     (
>     (<--- 3
>     (
>     (
>     (
>2 ___(
>     (
>     (____ 4
>
>The variac was originally connected to the mains at 1 & 2, and to the 
>outputs with 1 & 3. This gives a maximum of 140V.  If I connect the mains 
>to 2 & 5 and the outputs to 1 & 4 I get about 170V.  Any reason for these 
>extra bits of winding?
>
>-Adam

My guess is to allow the variac to be panel mounted with the base attached
to the panel, and the shaft extending through the bottom and through the 
panel.  Here one would want the 0 and 120% end points to be reversed from
the way they normally are, so that from the knob's perspective, 0% is (still)
CCW.  To accomplish this, the mains would go to 4 & 5 with 1 & 2 unused.

Gary Lau
Waltham, MA USA

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