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5A) Power Supply Units (PSUs).

The most common power sources for a beginner's Tesla coils are ignition coils (IC's), oil burner ignition transformers (OBITs), neon sign transformers (NSTs). These are all AC sources of power. There are also microwave oven transformers (MOTs) and potential transformers, also know as "pole pigs". I have not included DC power supplies here, as in my opinion DC coils are more the realm of experienced coilers.

A) Ignition coils (ICs). These are a great place to start, they can usually be obtained for free from dead cars or junkyards and generally don't kill people. Remember though, that if the output of an IC powered coil connects you to any part of the 60hz mains that electrocution is a very real possibility. There are a number of schematics for hooking up a IC PSU. While these supplies work well for small coils, they can be ruined instantly if improperly connected or used. Guess how I know that. Anyone need a dead IC? Click HERE for IC photos.

B) Oil burner ignition transformers (OBITS). These are commonly available, and are often easy to scrounge from heating and air conditioning businesses. Typical ratings range from 4kV to 7kV, usually at around 30ma current. While not as lethal as their larger cousin, the NST, they can still be deadly, although your chances of surviving a hit from one are fairly good. They seem reasonably robust for coiling, and are a good choice for second system or the first system of someone who comes to coiling with previous electrical experience. Click HERE for OBIT pictures.

C) Neon sign transformers (NSTs). These are far and away the most common power supply for TC work. While they aren't as inherently robust as one might like, with proper protection they are quite reliable. Safety gaps are required on a NST (or any other TC for that matter) to help prevent failure. Typical ratings range from 6kV @ 30 ma to 15kV at 120 ma. These transformers should be considered lethal! Click HERE for pictures of NSTs.

D) Microwave oven transformers (MOTs). These are not really a beginner's best choice. They are relatively low voltage for TC use, and so usually have a "voltage doubler". The are not current limited, and so must be ballasted to avoid problems. They are also very dangerous, as they can throw MASSIVE amounts of current through you. The up side is that they are easily obtained for free, and correctly used, their ability to produce lots of current is a big plus. These are NOT recommended for a beginner's coil, and I mention them here only because they are so often mentioned elsewhere.

E) Potential transformers or "pole pigs". You have now entered the definitely lethal zone. Any mistake with these WILL KILL YOU! As such, these are not for beginners. I personally have never made or operated a pig powered TC. I just don't have the space to store it, the power to run it, or a place to light it up. These transformers are great and robust for TC work, but require ballasting to prevent blowing all your breakers and generally melting everything into slag. I don't have any pictures or information regarding potential transformer systems.Again, I include them here as they are fairly common and frequently mentioned elsewhere.

Power supplies are often the determining factor in building a TC, meaning most people acquire or decide upon their PSU and then design the rest of the system around it. The voltage and current of a transformer dictates the range of capacitance required in the tank circuit. It also dictates the gauge of wire required in various parts of the system, the values for fuse protection and a number of other things. Once you have decided upon a PSU, it is time to design the rest of your system. If you are lazy or mathematically challenged as I am then use one of a number of useful programs available to do the required calculations. My favorite is JAVA TC.

The control of a PSU is one of the most important aspects of safety in coiling. In the shock accident I described earlier with the NST, I had the transformer foolishly directly wired to a cord and plugged into an outlet. So if I had been unable to release my grip, there was no way to turn it off without yanking the plug. My current controller has a "power on" key switch, a momentary style switch for primary activation, and indicator lights that show when power is available to the primary circuit. As well, I have a red indicator mounted on the transformer itself that shows when voltage is present. In order to run the coil in continuos mode, for testing or when I need both hands free during operation, a second key switch must be turned. While it is still possible to have an accident with these safety features, the risk is reduced, and several deliberate acts are required to light the coil up. Click HERE for pictures of my controller.

Variacs, while not essential, greatly increase safety and decrease the chances of ruining equipment by allowing lower voltage testing and ramped application of voltage. They also allow you to increase the power input to your PSU to around 140vac, gaining you some sparks! They do present some safety issues of their own however. Never assume that a variac is off unless it is switched off or unplugged. With the dial set at zero it is still possible for a few volts to trickle through. In a 15kV NST, a few volts on the primary side will produce hundreds of volts on the secondary side, plenty enough to give you a nasty jolt. Quality variacs have a switch built into them that cuts the power when the dial is turned all the way to zero, but many cheaper variacs or ones scrounged from older equipment do not have this feature. Click HERE for variac pictures.

A note on fusing variacs: I set the fuse values in my variacs depending on the load I expect to run, not the maximum rating of the variac. So if I'm only expecting to pull 10 amps from a 20 amp variac, I'll use a 10 amp fuse. This isn't so much for the variacs sake, but to protect what I am working on. As well, it serves as an indicator of excessive power consumption, and by successively increasing fuse ratings, you will determine what the system really draws at peak, and when those peaks occur.

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