A line output transformer are used in cathode ray tube in which the transformer generates high voltage which is needed as part of the supply of a CRT display or other devices such as plasma globes. A line output transformer generates voltage from a few kilovolts to 20 to 30 kilovolts which is used in a color TV tube. A line output transformer is not like normal transformer that uses a alternating current of 50 or 60 hertz. These transformer operates with switched currents at higher frequencies, they operate in the range of 17 kHz to 50 KHz.
How Does a Line Output Transformer Works
A line output transformer not only are designed to transfer energy, but also to store energy for a significant fraction of the switching period. To achieved this, the line output transformer coils are winded on a ferrite core with an air gap. The air gap increases the reluctance of the magnetic circuit and consequently its capacity to store energy.
The primary winding of a line output transformer has a low voltage sawtooth wave. The sawtooth wave is ramped up which sweeps the beam across the screen to draw a line. The wave is abruptly switched off which causes the beam to quickly fly back from the right to the left of the display by the horizontal output stage. The vertical portion of the sawtooth wave is extremely useful to the line output transformer, the faster a magnetic field collapses, the greater the induced voltage. This high frequency also reduces the size of a transformer so it can be used in television sets and computers. In TV sets the frequency is about 15 kilohertz and in computer displays the frequency can vary from 30 kHz up to 150 kHz.
The construction of a line output transformer the primary is wound around a ferrite rod and around this the secondary. The reason for this it reduces the leakage inductance of the primary. Around this is an ferrite frame closing the magnetic field lines. They place a gap between the rod and the frame which produces a air gap which reduces the remanence. The secondary enameled wire is wrapped with layer after layer of mylar film. The reason for this it has more dielectric material between them to protect parts of the wire against high voltage. The outside of the winding which receives the highest voltage has extra insulation and screening to protected the surrounding. Each layer of the windings is connected by a rectifying diode to the next layer to avoid some stray capacitance. Windings go up the rod and the diodes go down. The Ac voltage increases along the rod and the DC voltage increases radial from inside to outside.
We hope we have given you a insight on how
a line output transformer works. For more
information or if you are interested in purchasing a line
output
transformer call TEMCo to speak to their many highly trained
specialists. TEMCo is a family own business and has been in
business for over 40 years. TEMCo only sells quality made
output transformers including top manufacturer like
Hammond output transformer. For
all your
transformer needs call TEMCo at
1-510-490-2187
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