Poor PF spark gap motors - Kill-A-Watt power meter test - Input power measurement

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

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi,

For my spark gap motor:

http://hot-streamer-dot-com/TeslaCoils/MyCoils/SmallCoil/small_power.jpg

The Kill-A-Watt reports:
118.6 Volts
4.91 Amps
177 Watts
0.30 PF
584 VA
59.9 Hz

So I guess the spark gap motor in my small coil draws more current than the 
NST!!  I never realized it was that bad.  The motor only needs 1.49 real 
amps to run.  Might as well correct for the 3.42 amps reactive.

3.42 = 118.6 / Xc   Xc = 34.68 ohms

34.68 = 1 / (2 x pi x 60 x C)    C = 76uF.  Four 20uF should do it...

So with 80uF I get
116.6 Volts
1.81 Amps
174 watts
212 VA
0.82pF

Saves three amps!  I checked with my strobe light and it did not seem to 
change the timing of the motor at all.

I tried my other bigger spark gap  (1/4 HP motor much much larger rotor) 
and got:

116.2 V
5.37 A
217 W
624 VA
0.34 PF

And again it is wasting about 3.5 amps...  So adding 80uF to 1/4 HP spark 
gap motors can reduce the system current draw by about 3 amps.  Might be 
enough to stop breakers from blowing in some cases.

The Kill-A-Watt meter is pretty cool!!

Cheers,

         Terry


-----------------------

Hi Jim,

Sounds too good to be true.  However, it IS true!!!

http://hot-streamer-dot-com/temp/Kill-A-Watt/Kill-A-Watt.html

They are a bit hard to find at Radio Shacks so call first.  I worry a 
little about how they would like being next to a Tesla coil, but they seem 
basically very sound.

Cheers,

         Terry


At 08:16 PM 3/10/2003 -0800, you wrote:
>The "kill-a-watt" (that's the brand name) watt meter runs about $30-40 from
>all manner of sources (including Radio Shack), and measures VA, Watts, PF,
>etc. with an accuracy of better than 1%..