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Subject: Re: [Homebrew_PCBs] Re: drill pcb

From: Stefan Trethan <stefan_trethan@...>
Date: 2016-02-25

The point he makes, correctly, is that the tool does not need isolation since it is designed to operate directly on 220V anyway.

Many of the 220->110 and 110->220 converters sold are autotransformers.

ST

On Thu, Feb 25, 2016 at 2:57 AM, rolohar@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:


Perhaps I do not understand exactly how the autotransformer would be used with the tool you are
planning to use.

A "real" autotransformer has only one winding, therefore there is no isolation between the power source and the
tool you are using, so it is possible that the user could be exposed to the full power from the source.

Please explain how you plan to use the "autotransformer" in this application....which is  (I believe) to
operate a 220 volt tool and a 120 volt power source.

Or, perhaps, the term "autotransformer" is not an accurate name of the device you want to use.
A step up or step down transformer would be cool.

Regards,

Roland

From: "craigl2@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 6:45:40 PM
Subject: [Homebrew_PCBs] Re: drill pcb

 

Since you would normally be plugging the drill into a 220 wall outlet directly how is plugging it into an autotransformer any less safe?


Craig



---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and
a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.
∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

 

Depends.  Most of them are autotransformers.  In this case, the full winding is used for 220 and it's tapped halfway down for 110.  I got my last two for free on CraigsList.



---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Aren’t most of these converters to convert 220 down to 120 ?

International voltage converters are widely available in the states.