Homebrew PCBs

Brad Thompson: 

My stupid error! 

Of course, there is a "core" in an autotransformer or "Variac". Often, not exactly like the "E" and "I" core elements in a conventional transformer, but nevertheless........there is a core. 

My comments regarding "isolation" are valid, and one must take caution when using an autotransformer. 

As mentioned, there are several very good (very valid) videos on YouTube regarding the use, and mis-use 
of variacs, autotransformers, etc. 

They deal mostly with the anatomy of 3-Phase power distribution systems, which most of our domestic 
power services are connect to, and how "Isolation" is an important factor to deal with, espcecially 
when connecting certain pieces of test equpment and certain power tools. 

"Isolation" vs "Insulation". 

Regards. 

Roland F. Harriston, P.D. 

----- Original Message -----

From: "Brad Thompson brad.thompson@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> 
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com> 
Sent: Thursday, February 25, 2016 9:15:15 AM 
Subject: Re: [Homebrew_PCBs] Re: drill pcb 





On 2/25/2016 10:39 AM, rolohar@... [Homebrew_PCBs] wrote: 

<snip> 

Variacs and autotransformers only have one winding. There is no 
primary/secondary winding 
configuration. There is no iron core to facilitate induction between 
the primary and the secondary 
windings. 
<snip> 
Hello-- 

There's most definitely an iron core in an AC-line autotransformer! 
There has to be because otherwise there would be 
no transformer action to step up or step down the incoming line voltage. 

As for troubleshooting older "hot chassis" equipment, for safety's sake 
always power the equipment with an AC-line 
isolation transformer. If you need to power a 120VAC item from a 240 VAC 
line (or vice versa), you can use 
a transformer **with isolated windings** designed exactly for this 
purpose. These are sometimes referred to as 
"industrial control transformers". 

73-- 

Brad AA1IP