[Boatanchors] Sola Constant Voltage Transformers

[Richard Knoppow]

----- Original Message ----- 
From: "David C. Hallam" <dhallam at knology.net>
To: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
Cc: "Boatanchors-qth" <boatanchors at mailman.qth.net>
Sent: Thursday, February 21, 2013 10:09 AM
Subject: Re: [Boatanchors] Sola Constant Voltage 
Transformers


>I gather you are saying they can be a good thing.  But, 
>don't leave it connected to the line when not in use.  I 
>was planning to use this one on a receiver so I probably 
>should use it with an outlet strip and turn off and on at 
>the strip.
>
> I suspected the no load current was high as it get hot 
> even with no load.
>
> David
> KW4DH
>
    I rechecked this today. The transformer is rated at 
about 2 A, that is 250 VA output. With the output 
disconnected it draws between about 1.5 and 1.8 amps 
depending on the voltage. The higher current is at minimum 
voltage for regulation, around 90 volts on this one.  At the 
maximum voltage the Variac will deliver, about 130 V the 
current drops to about 1.5 amps with no load.  I put a 100 
watt light bulb on it and it made no difference to the 
indicated current at any voltage.  The lamp brightness was 
constant over the range of about 85 to 130 volts.  I didn't 
have it running long enough to get hot but it has a warning 
printed on it to avoid touching because of burns.  I had one 
running on a receiver for a long time.  It got quite hot and 
"sang" sometimes.  OTOH, the receiver was on a line with a 
thermostatically controlled electric heater and never 
drifted. Without the regulator it sails around because the 
filaments are not regulated.
    I think the newer type Sola transformers are more 
mechanically quiet than the old ones and put out reasonably 
pure sine waves but they are still inefficient for low loads 
and get hot.  I think they work best with a load near 
capacity that is run pretty much continuously.
    About the only line regulator I know of that is 
reasonably free of these defects is the General Radio type 
of servo driven Variac but it has a set of vices all its own 
and does not provide the filtering or short circuit 
protection of the Sola.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com