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How Neon Works

How Neon Works,
and Differences Between Transformer Types

We sell both balanced and unbalanced output neon and plasma transformers. Balanced are center-point grounded, unbalanced are end-point grounded.

Balanced Transformers are preferred for conventional neon displays. They operate normally with a center point ground with two output power leads going to the opposite ends of the neon display. It is usually the objective of the installer to wire the display such that very limited ground current flows, and that all the current flows from one end of the neon tube to the other, providing a closed captive circuit and limited or no appreciable ground current. If a certain amount of ground current flows, it will trip a UL 2161 type transformer that has a built-in ground fault interrupt circuit (GFI). This phenomenon was never a real problem with the older “conventional” 60 Hz transformers. But modern solid-state transformers that have taken over the market operate at a much higher frequency, most around 25 kHz. And for reasons beyond the scope of this literature we can only say that most of the negative effects (balancing, resonance, high Corona) are more predominant when using the higher frequency solid-state modern transformers.

While Balanced Transformers are good for standard neon displays, they normally cannot be used for specialized neon or plasma displays which only require one power lead to energize (such as certain pieces of neon artistry, plasma globes and the like), which is where unbalanced transformers come in.This is because when only one lead is being used, the ground current must flow through the body of the display (the glass back to the power supply ground) to complete the circuit. This current is capacitive, meaning that it’s not exactly in phase with the voltage. This means that every once in a while single ended installs can run into a resonant situation, and this resonant phenomenon is not understood by most neon installers. When 60 Hz transformers were first tried on single ended displays, it was noted the displays were very dim. But once high frequency transformers were developed, single ended operation was made possible. However other cautions had to be observed such as resonant rise, interference with adjacent nearby displays, in certain instances annoying burns or pinprick sensations when near a single ended display, more attention paid to high-voltage wiring procedures for the installs, etc. The resonant rise condition became very predominant and sometimes caused excessive secondary coil heating, unstable operation (especially when systems were adjacent to one another), and many other strange issues. One way to prevent resonant rise from happening in a single ended display is to make sure there is a large inductance in the secondary coil such that resonance becomes almost an impossible situation.

Most installers are aware that a neon transformer is current limited by the inductance of the secondary leakage reactance with the primary. It is this leakage reactance that limits the current to the display. Without the leakage reactance, the display would continually draw current until it exploded or the transformer burnt out. This phenomenon is known as a negative resistance, which is common with electrical discharge in a gas where the current produces ionized particles, then the ionized particles promote more current (the ionization allows the current to flow more easily with less resistance), and soon there is a runaway effect. (This is opposite to most normal loads that we are familiar with such as motors, filament light bulbs, TV sets, etc., where an increased current sees the same or increased resistance.) So the leakage reactance of the transformer controls this current runaway, and is a prime factor in determining the short circuit secondary current.

It is beyond the scope of this data to get into the complex notation that is necessary to fully explain this mathematically. However a person with this knowledge can use this effect to do useful things in neon lighting, especially special effects, but it is not advised for a person not fully understanding of why this happens. Most installers doing normal balanced neon signs will very rarely run into this problem. And those that are installing single ended devices normally will not run into it if using a properly made transformer or power supply. This is what we at INFORMATION UNLIMITED supply to our customers to prevent these things from occurring. If you do have a problem with your installation or setup, you may call our technical department and we will quickly help you determine what is needed to fix it.