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Registered Member #61373
Joined: Sat Dec 17 2016, 01:45PM
Location: San Antonio, TX
Posts: 87
I learned that resonant caps on a pole pig make the voltage double and compensate for leakage inductance, but if the houses electrical system was designed for such, wouldn't it be more efficient to include a resonant cap on each pole transformer? Will including a PF cap on the primary help correct PF, and the resonant cap boost total power output while using less energy from the substation?
I know that a pole pig has good PF and efficiency, but the PF cap can get the transformer closer to 100% eff. I'm still learning about resonance, and I know resonant caps on a pig make a huge power boost. The resonant caps will be tuned to 60Hz.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
I learned that resonant caps on a pole pig make the voltage double NO and compensate for leakage inductance what little there is on a pig, but if the houses electrical system was designed for such, wouldn't it be more efficient to include a resonant cap on each pole transformer? NO Will including a PF cap on the primary help correct PF Yes, but the primary inductance is so large that the PF hit is minimal, and the resonant cap boost total power output No while using less energy from the substation? No
I know that a pole pig has good PF and efficiency Yay! something right, but the PF cap can get the transformer closer to 100% eff By the sqrt(b'all) at the cost of a cap. I'm still learning about resonance, and I know resonant caps on a pig make a huge power boost Do they? why do you assert this?. The resonant caps will be tuned to 60Hz.
There's a big difference between MOTs and pigs, like the shunts introduced into a MOT to raise the leakage inductance, to resonate out some of the doubler rectifier capacitor impedance.
Registered Member #61373
Joined: Sat Dec 17 2016, 01:45PM
Location: San Antonio, TX
Posts: 87
Dr. Slack wrote ...
I learned that resonant caps on a pole pig make the voltage double NO and compensate for leakage inductance what little there is on a pig, but if the houses electrical system was designed for such, wouldn't it be more efficient to include a resonant cap on each pole transformer? NO Will including a PF cap on the primary help correct PF Yes, but the primary inductance is so large that the PF hit is minimal, and the resonant cap boost total power output No while using less energy from the substation? No
I know that a pole pig has good PF and efficiency Yay! something right, but the PF cap can get the transformer closer to 100% eff By the sqrt(b'all) at the cost of a cap. I'm still learning about resonance, and I know resonant caps on a pig make a huge power boost Do they? why do you assert this?. The resonant caps will be tuned to 60Hz.
There's a big difference between MOTs and pigs, like the shunts introduced into a MOT to raise the leakage inductance, to resonate out some of the doubler rectifier capacitor impedance.
Ok, I stand corrected . I have a question though. In a pole pigs case, why do the arcs become longer and brighter when people add a resonant cap to them if it only gives the pig a marginal power boost (hobbyists making arcs, not for industrial use)? Can you please explain what's going on, and how the cap makes the arcs much longer?
I understand how this would apply to Mots and other less efficient transformers, but not to a very efficient pig.
Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
That's because the pole transformer requires a ballast. If the HV coil was shorted without ballasting, the transformer would attempt to draw a few hundred kVA from the mains. So the 'resonant' setup usually involves a large inductive ballast in series with the mains input, and the capacitor in series with the HV winding. The capacitor is not resonating with the transformers leakage inductance, which is very small.
Registered Member #61373
Joined: Sat Dec 17 2016, 01:45PM
Location: San Antonio, TX
Posts: 87
GrantX wrote ...
That's because the pole transformer requires a ballast. If the HV coil was shorted without ballasting, the transformer would attempt to draw a few hundred kVA from the mains. So the 'resonant' setup usually involves a large inductive ballast in series with the mains input, and the capacitor in series with the HV winding. The capacitor is not resonating with the transformers leakage inductance, which is very small.
So what role does the cap play, and how does it boost power so much if it doesn't resonate with anything?
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
ScottH wrote ...
GrantX wrote ...
That's because the pole transformer requires a ballast. If the HV coil was shorted without ballasting, the transformer would attempt to draw a few hundred kVA from the mains. So the 'resonant' setup usually involves a large inductive ballast in series with the mains input, and the capacitor in series with the HV winding. The capacitor is not resonating with the transformers leakage inductance, which is very small.
So what role does the cap play, and how does it boost power so much if it doesn't resonate with anything?
The point was that it does resonate with the ballast inductor, cancelling its effects, leaving you with an effectively un-ballasted transformer, from which a greater current can be drawn.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Echoing Grantx's post, link me a video of an arc being drawn from a pig, without any ballast, then with capacitive ballast, and we'll see which is brighter.
There is inherently nothing in a pig that can be resonated. The leakage indutance is minimal, the primary inductance is very large so its admittance is minimal, the secondary inductance is short-circuited by the low impedance grid connected to the primary.
There are two general types of transformer. Ideal transformers, where all parameters are as ideal as economically possible, and non-ideal transformers, where one or more parameters that would be a defect in an ideal transformer is designed up to a specific figure. In a pig, and indeed most power transformers, primary inductance is as near infinity as possible, leakage inductance as close to zero as possible. In a MOT, leakage is added with the magnetic shunts to resonate out some of the doubler capacitor impedance. In a flyback transformer, air-gaps are introduced to reduce primary inductance so more energy can be stored. In an NST, shunts increase the leakage inductance to limit the current delivered into a neon tube.
Registered Member #61373
Joined: Sat Dec 17 2016, 01:45PM
Location: San Antonio, TX
Posts: 87
hen918 wrote ...
ScottH wrote ...
GrantX wrote ...
That's because the pole transformer requires a ballast. If the HV coil was shorted without ballasting, the transformer would attempt to draw a few hundred kVA from the mains. So the 'resonant' setup usually involves a large inductive ballast in series with the mains input, and the capacitor in series with the HV winding. The capacitor is not resonating with the transformers leakage inductance, which is very small.
So what role does the cap play, and how does it boost power so much if it doesn't resonate with anything?
The point was that it does resonate with the ballast inductor, cancelling its effects, leaving you with an effectively un-ballasted transformer, from which a greater current can be drawn.
So having the cap is just like hooking up the transformer with no ballast? If that's the case, why not hook up the pig unballasted, and save the cost of an inductor and Hv cap?
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
ScottH wrote ...
hen918 wrote ...
ScottH wrote ...
GrantX wrote ...
That's because the pole transformer requires a ballast. If the HV coil was shorted without ballasting, the transformer would attempt to draw a few hundred kVA from the mains. So the 'resonant' setup usually involves a large inductive ballast in series with the mains input, and the capacitor in series with the HV winding. The capacitor is not resonating with the transformers leakage inductance, which is very small.
So what role does the cap play, and how does it boost power so much if it doesn't resonate with anything?
The point was that it does resonate with the ballast inductor, cancelling its effects, leaving you with an effectively un-ballasted transformer, from which a greater current can be drawn.
So having the cap is just like hooking up the transformer with no ballast? If that's the case, why not hook up the pig unballasted, and save the cost of an inductor and Hv cap?
Yup, you have to look at these sources very carefully to discover exactly what's happening, what's being claimed, what the circuit is etc etc
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Why don't pole transformers that supply your house have resonant caps added on?
. I have a question though. In a pole pigs case, why do the arcs become longer and brighter when people add a resonant cap to them if it only gives the pig a marginal power boost (hobbyists making arcs, not for industrial use)? Can you please explain what's going on, and how the cap makes the arcs much longer?
