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I obtained a pole pig

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J. Aaron Holmes

Thu May 01 2008, 02:11PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

This is all getting terribly OT. If you all want to talk about burning up light bulbs, you should start to new topic.

Cheers,
Aaron, N7OE

teslacoolguy

Thu May 01 2008, 04:50PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

I can totally agree with that J. Aron Holmes and i have one more question about the pig. What kind of PFC caps do i need to use?

J. Aaron Holmes

Thu May 01 2008, 11:57PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

teslacoolguy wrote ...

What kind of PFC caps do i need to use?

I wouldn't waste my time. PFC might be worthwhile if you were trying to parallel a bunch of NSTs and not trip the 15A breaker on some existing 120V socket inside your house. Otherwise, since you'll probably have to install your own dedicated 240V "pig socket" in your garage, just give yourself some headroom there and be happy.

Cheers,
Aaron, N7OE

Chris

Fri May 02 2008, 01:59AM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

I would not be so quick to ignore power factor. If you're running this thing on a 50A or 60A breaker, you will find yourself significantly limited if you don't correct.

First you need to know the apparent power |S| of the pig with the appropriate load on that you will be using. This is just the RMS voltage times the RMS current at any voltage (you can use a low voltage to test since you have a variac, and the power factor is not dependent on voltage). You also need to know the phase angle between the voltage and current or the impedance angle. You can just calculate all this at once if know the inductance of the pig with the appropriate load on (which you could measure or calculate). The impedance Z of an inductor with resistance is R + iwL where L is the inductance, R is the DC resistance, and w is the angular frequency (in radians per second, just 2pi*frequency), so the RMS voltage and phase V(<) = (R + iwL)I where I is the current. The power factor p is the cosine of the voltage phase angle minus the current phase angle, which is the same as the cosine of the angle portion Ã˜ of the complex impedance Z. Now you can calculate the reactive power Q needed for the pfc cap. Q = |S|sin(arccos(p)) = |S|sin(Ã˜). Commercial pfc caps specify this rating on them in VAR or kVAR. To find the capacitance in farads, divide Q by the the square of the RMS voltage, then by the angular frequency. wC = |Q|/(V^2)

Note that with pure inductance the phase shift will always be 90 degrees, thus power factor (cos90) is zero.

teslacoolguy

Fri May 02 2008, 02:12AM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

ok I wont worry about power factor correction and now what you all have been waiting fo, i have a pic

I picked it up today so i cant wait to test it.

Chris

Fri May 02 2008, 03:11AM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

Cool. How are the taps set up inside? Mine has two separate low voltage windings so it can be wired for 240V or 240/480V center tap. It also has an adjustable tap inside that can change the voltage by +/- 5-10%. Does it have PCB oil?

Keep in mind that with a high power DC load (like an arc) your power factor will be HORRIBLE; perhaps it specifies on the nameplate somewhere but I might guess 0.6-0.7 at 10kVA (6-7kW). Of course the only way to know exactly for a given load is by knowing the total inductance and resistance. A bigger breaker only helps to a degree, but the more you draw the worse the power factor is, especially as you get up around 20kVA or more. This will be even worse with an inductive ballast on there since it ultimately depends on the ratio of inductance to resistance. The ballast inductance should be added in too if choosing a pfc cap. Pigs are designed to power a highly resistive load (like a bunch of lightbulbs, etc) with no ballast, not a low resistance load (arc, near short, etc) through further reactive ballasts. There is almost no way to fudge around this without using capacitors unless you're keeping to relatively low power stuff. With a tesla coil, the tank cap could be chosen to match (at least to some degree) the reactive power of the pig from the high voltage end; it doesn't matter which side you put pfc on. In theory you don't even need a ballast on the line side if you are soft starting something with a consistent load that is within the pig's ratings, like a properly designed tesla coil, but if there is a fault you will obviously be glad to have one. Anyways a few big motor-run caps on the low voltage side, or some power line pfc caps (I managed to find a few for $15 each at the recycling place) on the high voltage side could both work equally well for pfc. It is something that will be worth looking into if you are after serious power.

RogerInOhio

Fri May 02 2008, 03:21AM

Registered Member #1034 Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154

How about burning out a good bulb with high voltage.

Ok, I put in a good 60 watt bulb and the power supply burnt the filament almost instantly causing a big arc inside the bulb as shown in the first picture. The second picture shows it still arcing about 15 seconds later.

lpfthings

Fri May 02 2008, 10:04AM

Registered Member #1361 Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305

Even those things look scary WITHOUT being powered up! Look like a giant cap that will blow you apart if you touch it.

dingo27

Fri May 02 2008, 10:40AM

Registered Member #890 Joined: Tue Jul 10 2007, 10:06PM
Location: Slovakia
Posts: 180

i will never ever touch that (even if i coud get money )...

what is HV output and input? i am interested, because i never heared about that. Is it some kind of HV transformer?

teslacoolguy

Fri May 02 2008, 11:40AM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

The high voltage output is 14,900v to 23,000v and the input is 120-220v,

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