This document discusses the generation of high-frequency AC high voltages using a Tesla coil. It explains that a Tesla coil is a resonant transformer that uses a primary coil fed by a DC or AC supply through a capacitor to induce high self-excitation in a secondary coil. The primary and secondary coils are air-cored and tuned to resonate at frequencies between 10-100 kHz using additional capacitors. This generates high voltage outputs in the secondary coil of 500-1000 kV that can be used for testing or other applications requiring high frequency high voltages.

1. GENERATION OF HIGH - FREQUENCY AC HIGH
VOLTAGE :
Submitted By,
M. Pratheep ,
ICE – 4th Year ,
SCE, Trichy.

2. GENERATION OF HIGH - FREQUENCY AC HIGH VOLTAGE :
 High Frequency AC High Voltage are required for rectifier dc power
supplies. Also, for testing electrical apparatus for switching surges,
High Frequency AC High Voltage damped oscillations are needed
which need high voltage high frequency transformers.

3. ADVANTAGES OF HIGH FREQUENCY TRANSFORMER :
 The absence of iron core in transformers and hence saving in cost and size,
 Pure sine wave output,
 Slow build-up of voltage over a few cycles and hence no damage due to
switching surges, and
 Uniform distribution of voltage across the winding coils due to subdivision of
coil stack into a number of units.

4. TESLA COIL :
 The commonly used High Frequency AC High Voltage resonant transformer is the
Tesla coil, which is a doubly tuned resonant circuit shown schematically in Fig.
 The primary voltage rating is 10 kV and the secondary may be rated to as high as
500 to 1000 kV. The primary is fed from a d.c. Or a.c. Supply through the
capacitor C1.
 A spark gap G connected across the primary is triggered at the desired voltage
V1 which induces a high self-excitation in the secondary.

5. TESLA COIL :
 The primary and the secondary windings (L1 and
L2) are wound on an insulated former with no
core (air-cored) and are immersed in oil.
 The windings are tuned to a frequency of 10 to
100 kHz by means of the capacitors C1 and C2.

6. TESLA COIL :

7. TESLA COIL :
 The primary coil is wound on an insulator fibre tube of about 1 m length to represent a
cylindrical or helical winding and consists of a few tens of turns (usually copper strip or
tubings).
 The secondary winding is spaced quite away from the primary winding on another concentric
fibre or pyrex tube with a few thousand turns. The whole assembly will be immersed in an
oil tank under pressure.
 With separate bushings taken out for the primary and the secondary windings, the primary
winding is supplied through a high voltage capacitor rectifier unit rated for 10 kV to 50 kV or
more and the power rating of the transformer may be 10 kVA or more.

8.  The output voltage V2 is a function of the parameters L1,L2,C1,C2, and the mutual inductance M.
Usually, the winding resistances will be small and contribute only for damping of the
oscillations.
 The analysis of the output waveform can be done in a simple manner neglecting the winding
resistances. Let the capacitor C1 be charged to a voltage V1 when the spark gap is triggered. Let a
current i1 flow through the primary winding L1 and produce a current i2 through L2 and C2.
1

9.  The Laplace transformed equations for Eqn 1 is,
where I1 and I2 are the Laplace transformed values of i1 and i2.
 The output voltage V2 across the capacitor C2 is,
{ where V2(s) is the Laplace
transform of V2 .}

10.  The solution for V2 from the above equations will be ,
 K= coefficient of coupling between the windings L1 and L2.

11.  The peak amplitude of the secondary voltage V2 can be expressed as,
 The output waveform is shown
in Fig.

12.  A more simplified analysis for the Tesla coil may be presented by considering that the
energy stored in the primary circuit in the capacitance C1 is transferred to C2 via the
magnetic coupling. If W1 is the energy stored in C1 and W2 is the energy transferred to
C2 and if the efficiency of the transformer is η, then ,
 It can be shown that if the coefficient of
coupling K is large the oscillation High
Frequency AC High Voltage is less, and
for large values of the winding resistances
and K, the waveform may become a
unidirectional impulse.

13. !...THANK YOU…!
Email ID : pratheepm2001@gmail.com