"Larry Jaques" wrote in message
...
On Sat, 10 Jun 2017 07:51:41 -0400, "Jim Wilkins"
wrote:
"DoN. Nichols" wrote in message
...
On 2017-06-09, Jim Wilkins wrote:
"DoN. Nichols" wrote in message
...
On 2017-06-08,
wrote:
[ ... ]
I say "for house use" because there are also 240VAC industrial
versions, which have an additional (center) tap. You can feed
in
120
VAC between one end and that center tap, and get up to 240 VAC
output
(at the cost of lots more current from the 120 VAC line than you
feed
out at 240 VAC, of course.
The Superior Electric "Powerstat" is pretty much the same,
including similar voltage taps.
The maximum output current decreases considerably as the brush
moves
above the line voltage. My 10A 120/240V Powerstat 236 is rated
for
only 4A at 120V in, 240V out. Trying to pull more current loads
it
down.
O.K. That makes sense. I've never had to deal with that
problem. And I don't have one on hand to read the current limits
from
the data on the terminal block.
Try this. It's too big for me to check with my limited dialup
bandwidth or monthly cellular data allocation.
http://lcweb2.loc.gov/master/mbrs/re...og%20P258G.pdf
From my download of the Powerstat catalog C7002-1:
"CONSTANT CURRENT LOAD: Output that can be carried regardless of
output voltage setting.
CONSTANT IMPEDANCE LOAD: loads such as incandescent lamps or
resistance heaters in which the current drawn is approximately
proportional to the applied voltage, increasing to maximum current
at
line voltage. These ratings apply only to units having maximum
output
voltage limited to line voltage."
Their tech support confirmed the catalog's 5A Const I, 7A Const Z
rating of a Type 21 whose nameplate gave 3.75A as the limit.
Is there much difference between them? How was that handled?
Huh? Those ratings all apply to the -same- unit, depending on how it's
used.
This shows an 'improved' model, full 10A, which apparently took the
place of the others.
http://pubs.acs.org/doi/abs/10.1021/...nalCode=iechad
The article is dated 1959. I have the 5A version of that rectangular
VARIAC with the handle and two-prong ungrounded outlet on top.
I buy them old, cheap and hopefully repairable at flea markets. My 3A
Powerstat 10Bs were salvaged from a brand new machine (~1975) that
fell off the customer's forklift and landed face-first on them. They
broke in different ways and I was able to reassemble a basket of them
into several good (?) ones.
The one I used to tame the buzz box welder transformer was on the
front panel from a 1950's power supply.
When I tested a type 10 at its 3.0A Const Z rating an IR thermometer
indicated the brush temperature as 100C. It was driving a 24VAC
250VA
control transformer with a rectifier / capacitor output. The
combination is well matched and makes a decent 10A variable power
supply and battery charger. It will provide 15A briefly, until the
Powerstat and transformer primary overheat.
I added the output capacitor to stabilize the readings of digital
volt
and amp meters.
http://www.ebay.com/itm/DC-0-30V-0-1...#ht_1505wt_868
Found a less expensive precision ammeter for your charging circuit,
in
case you're interested: http://tinyurl.com/y7bns73g
"Input impedance: 10Euro"
Thanks for looking, but I buy little stuff mainly from Amazon to limit
exposure of my credit card, and check my account afterwards.
I think a voltmeter that reads ##.## is good enough to determine the
State of Charge of batteries, though I couldn't pass up that 5-1/2
digit Fluke for $25. 5% accuracy from 1ma to 10A is probably fine for
current. I checked my 15-year-old truck battery at 200A this morning,
it wouldn't matter if it was really 180A or 220A. At the low end
knowing the key-off battery drain to within 10mA should show me if a
relay sticks closed.
-jsw