[AMRadio] 220 volt AC Power Question

Jay Rusgrove JRusgrove at comcast.net
Mon Oct 30 21:03:37 EST 2006


As coincidence would have it I'm working on a Harris/Gates HFL1000 amplifier that can be wired to
run off either 120 or 240 volts. The unit has some 120 volt only transformers, blowers, relays and
other circuits. The way they handle this when operating on 240 is to use a 240/120 autotransformer.

Jay W1VD

----- Original Message ----- 
From: "Jim candela" <jcandela at prodigy.net>
To: "Discussion of AM Radio in the Amateur Service" <amradio at mailman.qth.net>
Sent: Monday, October 30, 2006 8:09 PM
Subject: [AMRadio] 220 volt AC Power Question

> Hi all,
>    I am building an amplifier that has a combination of 220 volt and 120
> volt transformers. The HV plate supply is 220V, and the rest is 120V. I will
> be keying the plate supply. My 220V outlet has phase, phase, and ground.
> There is NO neutral. The outlet is not a GFCI outlet so ground current will
> work, BUT.
>   The BUT here is whether this is legal with the National Electric Code?
> Before you say NO, consider the electric clothes dryer. These all run off
> 220V, and have 3 prong power cords. I have heard that in some dryers there
> are 120 volt loads (lights, and timer) as well as 220V (heater and motor).
> If this is true, then my approach must be OK so long as my power switch uses
> a DPST switch and (double fuses)to insure everything is off when it is in
> the OFF position.
> Comments please...
> BTW, I do have a 240/120 autotransformer of suitable size (VA rating), but
> space does not permit it's use.
> Jim
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