Power factor correction capacitors?
nzoomed, Mon Oct 26 2015, 02:14AMI see these capacitors listed locally on an online auction, i was wondering if these are beneficial for tesla coil use?
I dont know much about power factor correction, but i believe you need some pretty sophisticated equipment to perform this.
I have a variac, is it as simple as putting these across the variac output, or do i need more complex switching circuitry?
Re: Power factor correction capacitors?
Signification, Sun Dec 13 2015, 03:05PM
A nice medium-sized Tesla coil with a simple NST (Neon sign Transformer) does not have to concern itself with power factor correction. Example: If you have a 12kV @ 30mA NST lying around and use 60Hz power, then a good matching capacitor (based n matching impedance's) would be around: 0.0067uF (6.7nF) @ 18kV to 20kv. IIRC, I got this capacitance value with a dozen carefully built small root beer bottles (using salt water, I got right at 0.56nF/bottle). This was in 1999 and today, the bottle cap series connection still reads 6.7nF!...honest...
Now, with a variac, can use:V=I/2*pi*f*C = 11,877 Vrms or 11,877 * sqrt(2) = 16,800 Vp, settable via the variac.
...maybe a start...
Signification, Sun Dec 13 2015, 03:05PM
A nice medium-sized Tesla coil with a simple NST (Neon sign Transformer) does not have to concern itself with power factor correction. Example: If you have a 12kV @ 30mA NST lying around and use 60Hz power, then a good matching capacitor (based n matching impedance's) would be around: 0.0067uF (6.7nF) @ 18kV to 20kv. IIRC, I got this capacitance value with a dozen carefully built small root beer bottles (using salt water, I got right at 0.56nF/bottle). This was in 1999 and today, the bottle cap series connection still reads 6.7nF!...honest...
Now, with a variac, can use:V=I/2*pi*f*C = 11,877 Vrms or 11,877 * sqrt(2) = 16,800 Vp, settable via the variac.
...maybe a start...
Re: Power factor correction capacitors?
nzoomed, Sun Dec 13 2015, 08:42PM
Im building a DRSSTC, not a NST tesla coil.
I believe these need a better power factor to run efficient
nzoomed, Sun Dec 13 2015, 08:42PM
Im building a DRSSTC, not a NST tesla coil.
I believe these need a better power factor to run efficient
Re: Power factor correction capacitors?
GrantX, Mon Dec 14 2015, 03:46AM
GrantX, Mon Dec 14 2015, 03:46AM
nzoomed wrote ...
Im building a DRSSTC, not a NST tesla coil.
I believe these need a better power factor to run efficient
An NST is a linear inductive load with a sinusoidal current draw. Power factor can be improved by placing a capacitor in parallel with the primary coil (displacement power factor, a difference in phase angle). But a DRSSTC is a big SMPS, which is a non-linear load that only draws large currents at certain points of the sine wave, leading to distortion. With a rectifier and smoothing capacitor current is only drawn when the mains voltage rises above the charge on the capacitor. A few capacitors wired across the mains input will help filter harmonics, but an active switching PFC circuit will be required if you're chasing high efficiency.Im building a DRSSTC, not a NST tesla coil.
I believe these need a better power factor to run efficient
Re: Power factor correction capacitors?
Mads Barnkob, Mon Dec 14 2015, 06:09AM
You need a line choke/inductor or active PFC in front of a DRSSTC.
Very short and incomplete chapter on it:
Mads Barnkob, Mon Dec 14 2015, 06:09AM
You need a line choke/inductor or active PFC in front of a DRSSTC.
Very short and incomplete chapter on it:
Re: Power factor correction capacitors?
nzoomed, Mon Dec 14 2015, 10:31AM
OK, interesting read. Looks like alot of money unless i can find the components cheap. I will worry about that until after my coil is complete and i can test its performance.
nzoomed, Mon Dec 14 2015, 10:31AM
OK, interesting read. Looks like alot of money unless i can find the components cheap. I will worry about that until after my coil is complete and i can test its performance.
Re: Power factor correction capacitors?
Mads Barnkob, Mon Dec 14 2015, 04:50PM
If you have a variac inbetween to ramp up the voltage it will also double as a line choke.
Mads Barnkob, Mon Dec 14 2015, 04:50PM
If you have a variac inbetween to ramp up the voltage it will also double as a line choke.
Re: Power factor correction capacitors?
nzoomed, Mon Dec 14 2015, 08:34PM
Yes i do have a Variac that i will be using.
Im looking out for a bigger one though, as I dont think its rated high enough for me to run the coil at full power.
Its only 8A, but i should be able to push 10A through it.
Im hoping i dont need much more than 10A at the wall to run my coil at 850Apk
Problem is i have no idea how much power i can push my coil to, as it appears my IGBTs will be able to handle 1500A.
So i could easily run my coil at 1000A if i set the OCD on the driver to allow this.
nzoomed, Mon Dec 14 2015, 08:34PM
Mads Barnkob wrote ...
If you have a variac inbetween to ramp up the voltage it will also double as a line choke.
If you have a variac inbetween to ramp up the voltage it will also double as a line choke.
Yes i do have a Variac that i will be using.
Im looking out for a bigger one though, as I dont think its rated high enough for me to run the coil at full power.
Its only 8A, but i should be able to push 10A through it.
Im hoping i dont need much more than 10A at the wall to run my coil at 850Apk
Problem is i have no idea how much power i can push my coil to, as it appears my IGBTs will be able to handle 1500A.
So i could easily run my coil at 1000A if i set the OCD on the driver to allow this.
Re: Power factor correction capacitors?
Mads Barnkob, Mon Dec 14 2015, 08:51PM
My DRSSTC1 had no problems eating 11A from the wall, OCD set at 500A, depends on your on-time/BPS, not so much your peak current.
Mads Barnkob, Mon Dec 14 2015, 08:51PM
My DRSSTC1 had no problems eating 11A from the wall, OCD set at 500A, depends on your on-time/BPS, not so much your peak current.
Re: Power factor correction capacitors?
nzoomed, Mon Dec 14 2015, 10:04PM
OCD is only for protection, but i want to set it at the maximum i can for my IGBT's.
That way i can control its output by means of the variac and MIDI interrupter depending on the supply available.
Others here have said that theirs of similar power to what mine will be will draw about 20A peak at the wall, but the 10A breaker will handle it because its not sustained long enough to trip it.
Is your mains 230v or 120v?
Ive been estimating based on similar coils using 120v mains, the current at the wall should be half of that with 230v mains if the coil is running at the same output.
The other thing i want to know is if there is any rule of thumb for the size of the coil and maximum power i can get before i get too many strikes to the ring?
I might have to raise the toroid if i get too many ring strikes.
nzoomed, Mon Dec 14 2015, 10:04PM
Mads Barnkob wrote ...
My DRSSTC1 had no problems eating 11A from the wall, OCD set at 500A, depends on your on-time/BPS, not so much your peak current.
Yes, thats true, i will have to play around with the MIDI interrupter.My DRSSTC1 had no problems eating 11A from the wall, OCD set at 500A, depends on your on-time/BPS, not so much your peak current.
OCD is only for protection, but i want to set it at the maximum i can for my IGBT's.
That way i can control its output by means of the variac and MIDI interrupter depending on the supply available.
Others here have said that theirs of similar power to what mine will be will draw about 20A peak at the wall, but the 10A breaker will handle it because its not sustained long enough to trip it.
Is your mains 230v or 120v?
Ive been estimating based on similar coils using 120v mains, the current at the wall should be half of that with 230v mains if the coil is running at the same output.
The other thing i want to know is if there is any rule of thumb for the size of the coil and maximum power i can get before i get too many strikes to the ring?
I might have to raise the toroid if i get too many ring strikes.
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