[TCML] power meter goes crazy
Gary.Lau at hp.com
Thu May 29 17:22:31 MDT 2008
Measuring current or power on a TC with a static gap is extremely difficult, due to the chaotic timing and power draw inherent in a static gap. And beyond that, I've had zero success using digital meters to measure anything on an operating TC. They just go bonkers.
I shared your frustration in determining what to use for a PFC cap, but it ultimately did help; just very difficult to determine the best value by measuring the current. The best you can do is look for a midpoint in the wildly swinging meter needle. Or perhaps something more creative - put a low value resistor in series with the mains and measure how hot it gets, with different value PFC caps installed, and choose the coolest running value, as a means of getting a relative long-term average current reading.
With an NST, a PFC cap will make a significant reduction in current (not power) draw, and may make the difference between tripping the breaker or not.
Regards, Gary Lau
> -----Original Message-----
> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
> Behalf Of David Nelson
> Sent: Thursday, May 29, 2008 10:07 AM
> To: Tesla Coil Mailing List
> Subject: [TCML] power meter goes crazy
> I have a cheap electronic (digital) power meter (about A$40). I put it in line with my
> 750W tesla coil (15/50 NST). Current varied from 3A to 8A - NST is rated 3.6A.
> Power varied from 700W to 2200W and power factor varied wildly from 30% to
> 80%. Does this seem right. Is it because of the nature of the meter? Interference
> from the coil? (about 4 meters away - 12 feet) Any comments?
> I can't help thinking that a PFC will actually help me out. I know this is a can of
> worms but even with all the discussion I am still uncertain about the need for a PFC
> cap. There are conflicting opinions I think. Any (definative) advice for NST use
> would be greatly apreciated.
> Dave Nelson
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