Re: Variac Help

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

Adding a resistive load to the dimmer will probably help.  Even something
like a 25W lightbulb in parallel with the NST will work wonders for
stabilizing the behavior of the dimmer running into a strange load
impedance.  We used to run phase control dimmers for PSC motor driven fans,
and encountered all kinds of weird effects (aside from acoustic noise) like
surging and poor low speed control.
Also, if you get a dimmer designed for a ceiling fan it will work better.

Bear in mind that a dimmer isn't going to change the peak output voltage,
but essentially changes the average power output from the NST.  The "primary
voltage" to "knob setting" is probably a pretty strange curve, unlike a
variac, where it's a nice 1:1 linear slope.

In terms of brands, Lutron is the dominant brand in consumer dimmers/fan
speed controls, and is probably the cheapest and highest quality (strange it
may seem, but that's ALL they make, so you get economy of scale)

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, November 22, 2003 8:56 PM
Subject: RE: Variac Help


 > Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com>
 >
 > I was about to reply with "No, a dimmer just won't work with an NST".
 > This question has been asked often on this List and that's the usual
 > response.  But since I happened to have a dimmer and had never
 > personally tried it, I thought I would.
 >
 > I was surprised to find that it did work - mostly.  It did occasionally
 > stop, and I had to turn the dimmer down to zero and then it would behave
 > nicely again.  I did notice that when the dimmer was full-on, that
 > performance would improve somewhat by shorting the leads, so 100% is
 > more like 90%.  And of course, there's no way to achieve the extra 20V
 > boost that a real Variac can provide, with a dimmer.
 >
 > But, if the intended application draws anywhere near the 30A that the
 > original poster's Variac is rated, the $8 dimmer will fry before you can
 > say "what was that?"
 >
 > Gary Lau
 > MA, USA
 >
 > Original poster: "Philip Brinkman" <peeceebee-at-mindspring-dot-com>
 >
 > Well, are you putting that variac between the wall outlet and a neon
 > sign
 > transformer? If so, you don't need it. Go to walmart and get an $ 8.00
 > lamp
 > dimmer with attaced cord, mine works fine on a 15000 volt 30 ma
 > transformer, it even has a RF filter in it.
 >
 >
 >   > [Original Message]
 >   > From: Tesla list <tesla-at-pupman-dot-com>
 >   > To: <tesla-at-pupman-dot-com>
 >   > Date: 11/20/2003 10:00:10 AM
 >   > Subject: Variac Help
 >   >
 >   > Original poster: "EMMETT SECREST" <secrest2032-at-msn-dot-com>
 >   >
 >   > I am in need of help on wiring of a Technipower 30A Variac.  I
 > purchased
 > it
 >   > used and there are no instructions. I don't want to toast it as it
 > was a
 >   > little on the expensive side so your assistance is appreciated.  It
 > has
 >   > five connection points in this order;
 >   >
 >   > 1  5  3  2  4
 >   >
 >   > 1 = one end of the coil
 >   > 5 = between connection 1 and the center tap
 >   > 3 = center point of coil
 >   > 2 = between the center point and the end of the coil, point 5
 >   > 5 = the other end of the coil
 >   >
 >   > This is a 130 volt single phase model that mounts inside a cabinet of
 > some
 >   > type and does not have it's own enclosure.. My question is which
 > points
 >   > does the 120V supply connect to and which points are the output. Also
 > where
 >   > would the safety ground connect.
 >   >
 >   > Thanks in advance for your help,
 >   >
 >   > Emmett
 >   >
 >   > _
 >   >
 >
 >