[Boatanchors] Line Voltage issues

[Robert Spooner]

The problem with autotransformers such as the Variac is that they are high enough impedance that you may see inordinate voltage fluctuation with changes in load unless the current rating is high relative to the current draw. My favorite solution is to use a filament transformer to buck the higher voltage down to the rated voltage for the equipment. As long as the secondary current rating is equal to or greater than the maximum AC current draw, the transformer will be adequate for the job.

73,
Bob AD3K

On Jan 5, 2015, at 4:30 PM, Richard Knoppow <1oldlens1 at ix.netcom.com> wrote:

> 
> ----- Original Message ----- From: "Bill W7KXB" <w7kxb at msn.com>
> To: <boatanchors at mailman.qth.net>
> Sent: Monday, January 05, 2015 12:19 PM
> Subject: [Boatanchors] Line Voltage issues
> 
> 
>> A few of us remember when the line voltage was 110 (+/_) (Back when?? )Then the utilities upped it to 115v....then 120v...Now I have 125v.  It's been a gradual increase over several generations. Old gear  is most happy with their specified primary power source of 110 or 115v.  It might tolerate +10%  but not at 120v+ line voltage.       Years ago I changed over to 130V incandescent bulbs because the 125 line was taking out the common 120v variety after a week or so.   By all means do what is necessary to adjust the primary input voltage back down to what ever the manufacture specified at the time.  Then fine tune it for proper filament voltage.  Look for a good ole RMS Line Meter* and a Variac from your favorite ham Swapmeet.  Or check on line for Expanded Scale  Scale (100-140VAC) Voltmeter Kit.
>> My 2 cent's worth AR
>> de kxBill  .  .
> 
>    I don't think there was ever a standardized voltage that applied to all areas. Even 60 Hz was not standard in all parts of the country, for instance while the City of L.A. DWP was 60 Hz some of the smaller companies and So Cal Edison were 50 Hz. Burbank and Glendale had 50 Hz power until the late 1940s, maybe later. AC voltages were 110, 115, 117, 120, 124 depending where you were, not including the higher voltages for industrial use. There is a tendency to increase voltage because of the increased demand. The IR loss is less so its cheaper to push up the voltage a little rather than use larger wire.  Of course house voltage could be brought back down but that would require changing all the pole transformers, also expensive.
>   I don't think there is a completely satisfactory solution to this unless your power company is willing to co-operate.  Good voltage regulation can be had by using a resonant transformer like a Sola constant voltage transformer but they tend to be noisy and are of only moderate efficiency, nonetheless the regulation is excellent. There are also mechanical regulators. I don't know who, if anyone, makes them now but General Radio used to make electronically controlled Variacs, not instantaneous but very fast and do not waste power or make noise like a Sola.  There are probably other ways, a UPS will do it but is an expensive way and has a set of vices all its own. For a radio set that does not use a lot of power a bucking transformer is probably the best way to knock down very high line voltages but, of course, it does not regulate.
> 
> 
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com 
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