RE: [CAD_CAM_EDM_DRO] Re: Variable Transformer

Hugh:

Thank you. I agree 100%.

Andy Wander
Verrex Corporation

-----Original Message-----
From: Hugh Prescott [mailto:hugh345@...]
Sent: Wednesday, June 29, 2005 10:44 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Variable Transformer

Andy

Having trained and worked in the medical X-Ray field for 35 plus years
grounding and isolation are bigger things that actual function. The X-Ray
industry is a major user of autotransformers in primary power circuits
safely with great attention to frame grounding.

There is something in all fields called "custom and practice" (C & P)
especially in electricity and electronics. This C & P has evolved since the
Edison & Westinghouse era. There is a large body of knowledge that simply
says that in certain situations you do certain things. It's the best way, it
the safest way.

In general we are dealing with plug in equipment for the most part on this
list or direct connected by the user who is not someone with long time
experience as a electrician or EE. The location of a lot of our equipment is
not in a nice factory that is OSHA inspected and in compliance with all
electrical standards.

The manufactures of our drives and powersupply know full well that there may
well be misswires in the site power such as reversed wired outlets, grounded
outlets installed with no ground wire or the ground pin jumpered to neutral
etc. To reduce their liability and to make something that works 99.4 percent
of the time the industry has developed a C & P of using isolation
transformers in powersupply designs. It gives the most safety and
performance with the least chance of the magic smoke leaving the system.

Venture outside of the C & P and you are on your own.

Hugh