K.R. Scott - Bipolar Tesla Coils:: Experimenter’s Guide (High Voltage Experimenter Series Book 2)

Bipolar Tesla Coils: Experimenters Guide K.R. Scott Copyright 2016 PREFACE This text is not meant to be a detailed engineering document on high voltage devices. It is written for educational and informational purposes only. There is no high level math, theory or analysis. The contents are a collection of empirical experience from making high voltage equipment over the years. There is an enormous amount of information online and in books for those who want the really technical stuff.

When building these devices, you can only calculate enough detail to get you into the ball park, and then it is a little trial and error, good engineering practice, testing, fixing and re-testing. This is not an in depth study; it is basic nuts and bolts. I am a retired (semi-retired) engineer, and for me, it is about the fun factor, so lets let our curiosity go wild, have some fun and be safe. Regards, K.R. Scott High Voltage Experimenter Series Willow-Tech Publishing Copyright 2016 K.R. Scott Copyright 2016 All rights reserved.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photocopied, recorded, or otherwise, without the prior written permission of the copyright owner. DISCLAIMER The author and publisher have made reasonable effort to present this information as clear, concise and accurate as possible. However, they cannot be held responsible for the use or miss-use of this material. We are not liable for any damages including (but not limited to) personal injury, property damage or legal disputes arising from the use of information contained in this book. DO NOT USE TESLA COILS AROUND PACE MAKERS, INSULIN PUMPS, OR HEARING AIDS. Bipolar Tesla Coil sold by CENCO 1920s I purchased this coil on Ebay.

With the exception of cleaning, it is in very good shape. I used the Tesla CAD program to calculate the capacitor value, I wired it up to a spark gap and a 9 kV / 30 ma neon transformer and it worked great after 95 years! Main problem was dust on the coil which came off with a paint brush. Dust on a secondary coil will reduce output. The residual electrostatic charge on the secondary attracts dust. Cenco Bipolar Tesla Coil Bipolar Tesla coil operate in wave mode whereas the typical vertical configured coils with the bottom end of the coil grounded, operate in the wave mode. The Wave Tesla Coil has the secondary coil grounded and is slightly more sensitive to tuning and coupling than a Bipolar Tesla Coil.

On Bipolar Coils the coupling is in the center area of the secondary with less problem of racing sparks typically caused by too tight coupling in the wave coil and/or insulation breakdown. A wave coil can be more dangerous as in some configurations, if there is a short, or a conductive spark (racing sparks) 60 Hz current can be carried on the secondary's high frequency current (less isolation between primary and secondary). There is one incident in the 1910s, when this happened to a stage performer and he was electrocuted. A Bipolar Tesla coil somewhat acts like an isolation transformer as the secondary is not grounded and is insulated from the primary coil. The bipolar Tesla Coil will give better performance than the wave coil and the discharges are more impressive. You can force the Bipolar Coil to operate in the wave mode by grounding one end.

A description of a HV discharge wand for drawing sparks in this configuration is in the last section of this book. Fig. B is the circuit that I prefer, as the spark gap acts as both an operating spark gap and as a safety gap. The capacitor seeems to run a little cooler and is less likely to fail. One thing that can be done, especially with door knob type ceramic capacitors, is to add a couple of fender washers seperated by a nut on each end of the cap to act as a heat sink. Capacitors can also be potted in paraffin for extra insulation and the paraffin absorbs a lot of heat before it will melt and acts as a heat sink.

You can also try different combinations of paraffin and canola oil. Beeswax works very well. Many of the old high voltage coils and devices where insulated using a mixture of beeswax and rosin. Beeswax and linseed oil will make a kind of self healing insulation gel. Try varous mixtures melted together to get the consistancy you want. Canola oil is used as a base ingrediant for some HV insulating oils.

It is one of the non-toxic replacement for PCBs. (Polychlorinated Biphenyls) Very toxic and is still found in old transformers, especially pole pigs and oil filled capacitors built before 1979. One of Teslas experimental coil setups. G Electrical power source P Primary Drive Transformer S Secondary Drive Transformer A, B Spark Gap Electrodes M Sheet mica configured close to electrodes to promote air flow. C, C Leyden Jars (Selected for equal capacitance value a, b - Spark gap closely adjusted. This is a schematic of Elihu Thomsons (1853-1937) Disruptive Discharge Coil based on Teslas patent #454,662. This is a schematic of Elihu Thomsons (1853-1937) Disruptive Discharge Coil based on Teslas patent #454,662.

Drive transformer: 15-20 kV. Compressed air quenched spark gap. Primary: 15-20 turns heavy copper wire. Secondary: 150 turns fine wire is wound on a glass cylinder. The coils where emerged in a tank of boiled linseed oil. This coil produced 150 kV.

Some of Thomsons later coils produced sparks over 60 inches long. SPARK GAPS A spark gap will arc instead of sparking if the current going through it, is to high i.e. using a MOT (Microwave Oven Transformer typically 2,500 volt @ 500 ma or 5,000 volts DC (when using the diode and capacitor voltage multiplier that was in the microwave oven. A Pole Line transformers (Pole Pig) wired backwards will incinerate a small or poorly made spark gaps. If you are going to use this much energy to drive the Tesla coil you need to use a rotary spark gap or multi-gap. In this case, the electrodes need to be tungsten and air cooled.

Note: These types of transformers are more dangerous than neon sign or oil ignition transformers. When an accidental contact occurs, there is a very high probability of electrocution or at the lease very bad burns. Other hazards with spark gaps are acoustic/electrical noise, hard UV light, shock hazards, fire and the production of large quantities of Ozone and Nitrogen Oxides. Ozone has a very pungent smell. You need good ventilation and outside air. SOME GENERAL OBSERVATIONS ABOUT SPARK GAPS Multi-gaps are better than a single gap.