Trigger transformer
Encyclopedia
A Trigger transformer is a small, usually ferrite cored transformer
used in applications requiring a high voltage pulse, typically to start ionization
of a gas to allow a current to pass.
. Capacitor
s inside the light are charged up to a relatively high voltage, roughly 300 Volts for small strobes. This voltage itself is not capable of ionizing the gas in the flash tube, and the tube will not fire. If the capacitors were charged to a voltage high enough to ionize the tube, the result would be no longer a flash, but a continuous arc as the voltage is sufficient to maintain ionization in the flash tube.
Once the main storage capacitor has finished charging, a smaller capacitor is discharged into the trigger transformers primary coil. A large magnetic pulse is generated inside the transformer, which is coupled to the secondary coil through the core. The secondary coil consists of hundreds, or even thousands of windings of very fine copper wire, much thinner than human hair. This creates a huge voltage differential spike, in the order of 2 kilovolts (2000 volts) or more, depending on the length of the flash tube, and the gas contained within the tube. This high voltage spike overcomes the resistance of the gas, and allows ionization
.
Once this ionization exists, the tube offers a much lower path of resistance
, for which the main storage capacitor can now release its energy into the tube extremely quickly. By this point, the main storage capacitor is recharging and the trigger transformer ready to create another high voltage spike, and the cycle repeats.
Although strobe lights are the most common use of trigger transformers, other devices such as arc lamps, gas laser tubes and even the common fluorescent light employ trigger transformers, however usually in a different form, such as using an electrical ballast
to provide both the high voltage spike, as well as current limiting to prevent the tube from drawing excess current.
Inductors are also commonly used in place of a trigger transformer, however are not considered transformers themselves, although similar in operation.
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
used in applications requiring a high voltage pulse, typically to start ionization
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
of a gas to allow a current to pass.
Uses
A commonly used device requiring a trigger transformer are strobe lights. Strobe lights consist of a tube containing an inert gas, such as xenonXenon
Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
. Capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
s inside the light are charged up to a relatively high voltage, roughly 300 Volts for small strobes. This voltage itself is not capable of ionizing the gas in the flash tube, and the tube will not fire. If the capacitors were charged to a voltage high enough to ionize the tube, the result would be no longer a flash, but a continuous arc as the voltage is sufficient to maintain ionization in the flash tube.
Once the main storage capacitor has finished charging, a smaller capacitor is discharged into the trigger transformers primary coil. A large magnetic pulse is generated inside the transformer, which is coupled to the secondary coil through the core. The secondary coil consists of hundreds, or even thousands of windings of very fine copper wire, much thinner than human hair. This creates a huge voltage differential spike, in the order of 2 kilovolts (2000 volts) or more, depending on the length of the flash tube, and the gas contained within the tube. This high voltage spike overcomes the resistance of the gas, and allows ionization
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
.
Once this ionization exists, the tube offers a much lower path of resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
, for which the main storage capacitor can now release its energy into the tube extremely quickly. By this point, the main storage capacitor is recharging and the trigger transformer ready to create another high voltage spike, and the cycle repeats.
Although strobe lights are the most common use of trigger transformers, other devices such as arc lamps, gas laser tubes and even the common fluorescent light employ trigger transformers, however usually in a different form, such as using an electrical ballast
Electrical ballast
An electrical ballast is a device intended to limit the amount of current in an electric circuit. A familiar and widely used example is the inductive ballast used in fluorescent lamps, to limit the current through the tube, which would otherwise rise to destructive levels due to the tube's...
to provide both the high voltage spike, as well as current limiting to prevent the tube from drawing excess current.
Inductors are also commonly used in place of a trigger transformer, however are not considered transformers themselves, although similar in operation.