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Energy transfer between Primary and Secondary

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LAN_403

Austin

Fri Aug 21 2009, 04:44PM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

Has anyone done research on energy transfer between primary and secondary windings. what would be a typical current flow through a secondary winding from a primary pulsing i dunno lets say 1000 amps. and the secondary has a resistance of about 193 ohms.

I am trying to calculate the voltage out of my secondary. But I guess I would need to know how much current is flowing as a result of the primary.

Secondary Voltage = I (in the secondary) * R (in the secondary).

Resistance of Secondary
Secondary = 8" Diameter and 2300 turns of #26 AWG
Resistance for #26 magnetic wire = 40ohm / 1000ft

C = pie * D
C = pie * 8" = 25.1327 In

Length of wire = 25.1327 in * 2300 / 12 = 4817.1 Ft
Resistance of wire = 4817.1 Ft * 40 Ohms / 1000 Ft = 192.684 ohms

HV Enthusiast

Fri Aug 21 2009, 05:58PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Just use a current transformer and measure the current of the secondary directly if thats what ye seek.

Sulaiman

Fri Aug 21 2009, 06:45PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

If you look on the web there are MANY oscillograms of
primary and secondary voltages and currents.

You need a good grasp of simultaneous differential equations for an exact solution.

A first approximation which ignores losses and arcs is to use conservation of energy;
all the energy that starts in the primary capacitor is transferred to the secondary capacitance
(Toroid + Coil)
Epri = 0.5 x Cpri X Vpri^2 = Esec = 0.5 x Csec x Vsec^2
so
Vsec = Vpri x SQRT(Cpri/Csec)
and
since Cpri x Lpri = Csec x Lsec as Primary & Secondary have the same resonant frequency

Vsec = Vpri x SQRT(Lsec/Lpri)

In practice there are many circuitry losses (e.g. the spark gap)
and there is corona and of course the desired result .. electric discharges.
So until arcs can be modeled accurately there can be no exact mathematical solution.

EDIT ..... WOW! My 1000th post.

Austin

Fri Aug 21 2009, 09:03PM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

Sulaiman wrote ...

If you look on the web there are MANY oscillograms of
primary and secondary voltages and currents.

You need a good grasp of simultaneous differential equations for an exact solution.

A first approximation which ignores losses and arcs is to use conservation of energy;
all the energy that starts in the primary capacitor is transferred to the secondary capacitance
(Toroid + Coil)
Epri = 0.5 x Cpri X Vpri^2 = Esec = 0.5 x Csec x Vsec^2
so
Vsec = Vpri x SQRT(Cpri/Csec)
and
since Cpri x Lpri = Csec x Lsec as Primary & Secondary have the same resonant frequency

Vsec = Vpri x SQRT(Lsec/Lpri)

In practice there are many circuitry losses (e.g. the spark gap)
and there is corona and of course the desired result .. electric discharges.
So until arcs can be modeled accurately there can be no exact mathematical solution.

EDIT ..... WOW! My 1000th post.

Grats on ur 1000th post! I'm still far away.

I was just looking for a rule-of-thumb or ball park estimate of the energy lost between the coupling of the two coils. But its sounds to me like its negligible? I was just curious how people compute the voltage rating of their coil. People just guess based on the length of the arc?

When designing a coil I thought it would be best to figure out how long you want the arcs and then work backwards.

Hazmatt_(The Underdog)

Fri Aug 21 2009, 09:26PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

There is a substantial loss between the two coils. This is due to coupling itself. With a k = .14, you're only transferring 14% of your energy to the secondary!

Austin

Fri Aug 21 2009, 11:44PM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

I made the assumption that all tesla coils were tightly coupled to insure maximum energy transfer between the two coils. Ifound out that is actually not the case and that a slow ring up actually increase the performance of a DRSSTC.

I didn't know that, I learn more and more every day.

for anyone that might be interested, here is a basic high level summary of how a Tesla Coil works essentially. I found this article useful because it explained why a slow ring up or a low K factor is important and how it improves performance.

It's kinda difficult learning about this stuff with no prior electrical knowledge or experience.

Antonio

Sat Aug 22 2009, 12:16AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Hazmatt_(The Underdog) wrote ...

There is a substantial loss between the two coils. This is due to coupling itself. With a k = .14, you're only transferring 14% of your energy to the secondary!

This is not true. Ignoring resistive losses and radiation, in a properly tuned Tesla coil all the primary energy eventually moves to the secondary circuit. Actually, the double resonance Tesla transformer is a trick to ensure efficient energy transfer in a transformer even with low coupling between the coils.

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