Re: Dumb question ...

....In other words, VA is the power rating, similar to saying 40 Watts. So a
40VA transformer cannot drive a 250W lamp.


"Daniel" <dxmm@xxxxxxxxxxxxxxxxxx> wrote in message
news:465d5249$0$13928$88260bb3@xxxxxxxxxxxxxxxxxxxx
Jeff Strickland wrote:

"Rich Webb" <bbew.ar@xxxxxxxxxxxxxxxxxx> wrote in message
news:gugp5392rv1fj1hgb7ccucfnd3j8ggv4iu@xxxxxxxxxx
On Tue, 29 May 2007 23:35:17 GMT, "Jeff Strickland"
<crwlr@xxxxxxxxxxx> wrote:

... mostly because I'm dumb.

What's the difference in a volt-amp and a "regular" amp?

I have a transformer that makes 24vAC, and is rated at 40 VA, but the
amp
rating is only 1.67.

I have a lamp (fiber optic system) that takes 24v and 250W, which works
out
to 10.4A. The VA rating does not give me the current I need, and when I
plug
the light in, the voltage drops because the draw exceeds the power by a
wide
margin.

http://en.wikipedia.org/wiki/Volt-amp is a starting point. To avoid
recapitulating what's explained better and in more detail elsewhere,
volt-amps and WATTS (not "'regular' amps") are the related
measurements.


Okay, so to distill it down, 40VA is not near enough to drive a 250w
light?

Actually, this is a bit moot because another multi meter in my fleet has
determined that the lamp is open. I can't explain why I couldn't figure
this out before I bought the new power supply ...


Gee, that Wikipedia explanation is a bit hard to understand, so here is my
attempt.

In D.C. circuits, the voltage peaks occur at the same time as the current
peaks, so the power in the circuit is found by multiplying the voltage
applied, i.e. if applying 6 volts causes 2.5 Amps to flow, the power
dissipated by the circuit is (6 x 2.5) 15 watts.

However, in A.C. circuits, the effects of the components in the circuits
can cause the peak current to not flow at the same time as the peak
voltage occurs. So you may apply 6 volts a.c. to a circuit, and at some
times 2.5 Amps a.c. may flow at some time, but because the 6 volts and 2.5
amps do not occur at the same time, it is, technically, incorrect to to
same the power in the circuit is 15 watts, it is correct to say that the
circuit draws 15 VA.

Daniel

--
Posted via a free Usenet account from http://www.teranews.com



.

Relevant Pages

  • Re: "Mysterious" system crashes
    ... Watts are both shown on an appliance tag, ... not the power rating of the UPS. ...
    (comp.os.vms)
  • Re: Classical EM Wave Propagation, attn: Androcles
    ... > |> amount of power expressed in watts ... > |> a property of an electric circuit by which an electromotive force is ... > | an electron to be attracted to a positron? ...
    (sci.physics.relativity)
  • Re: Zener diode regulator?
    ... numerous solutions, but nothing on the complex side of things will work for this application. ... If you're supplying 1A through a series element you *will* disspate at least 68 watts. ... The circuit probably needs no more than 100ma, but I wanted to have a reserve for future use of LEDs and such. ... I don't think I will need to handle 68 watts of power. ...
    (sci.electronics.design)
  • Re: How does one add a 12v trigger to an amplifier...?
    ... I wish to power on via the 12v trigger is a Mackie FR2600 high current ... It draws ac line power at 120 volts plugged into a 20 amp ... Those are audiophool watts, or "Peak Intermittent Modulated Power", i.e. ... more than 80% of the branch circuit rating. ...
    (sci.electronics.basics)
  • Re: Electrical question about splicing into one hot wire for a light from a set of hots for 220 circ
    ... side of the house where there is no convenient power access. ... Instead of having to run a new 110v circuit 150ft, ... would tapping into each hot lines with only 1 90 watt bulb. ... The package says 100 watts worth of light but only uses 23 ...
    (alt.home.repair)