Electrical equipment and instruments cannot operate safely via the high voltages associated with transmission and distribution systems. The input voltage must be decreased to acceptable levels before it reaches the component to avoid potentially unsafe conditions and equipment damage.
High-voltage transformers, also called potential transformers, are used to reduce or ‘step down’ high voltage values to lower safer values. Additionally, high-voltage transformers can be used to isolate equipment from high-power circuits.
Types of High-Voltage Transformers
Although there are different types of high-voltage transformers, they all operate with the principle of electromagnetic induction. The different types include:
Electromagnetic Transformers
These types of transformers are essentially conventional wire-wound transformers. Electromagnetic transformers consist of two primary components: A primary coil, which has a large number of turns, and a secondary coil, which has a lesser number of coil windings. When an electrical current is passed through the primary coil winding, a magnetic field is produced which, in turn, induces voltage in the secondary winding. Since the voltage generated is a function of the number of coil turns, the secondary coil outputs a lower voltage in accordance with the laws of electromagnetic induction.
Capacitor Voltage Transformers (CT, CVT)
As voltages get sufficiently high, the heavy insulation required for the transformer can become expensive. For these situations, capacitor voltage transformers are used. Although not as efficient as electromagnetic transformers, capacitor voltage transformers are usually more economical at higher voltages. These transformers consist of a series of capacitors which act as potential dividers to reduce the voltage before it gets to the transformer. As a result, the main transformer receives a smaller voltage at the primary coil and, therefore, requires less insulation.
Optical Voltage Transformer
An optical voltage transformer is a type of sensor that uses the Faraday Effect to directly or indirectly measure electric currents. As light passes through the magnetic field induced by the electrical current, rotation of the plane of polarization occurs in a manner which is linearly proportional to the magnitude of the magnetic field. Thus, the greater the current, the greater the magnetic field, and the larger the angle of polarized rotation.
Application of High-Voltage Transformers
High-voltage transformers are used in any application that requires voltage to be reduced to a level that can be used by the component receiving the voltage. For example, power from a hybrid vehicle’s battery is fed to the primary winding of the transformer. The voltage is then stepped down via the secondary winding and ultimately supplied to various electronic components in the vehicle, such as the electric traction motor.
These transformers can also be used to support plasma generation equipment. Custom coils can be used to step up voltages to sufficiently high levels where plasma is produced. Wind turbines and other forms of alternative energy sources use high-voltage transformers to transmit power to the required areas of consumption.
Other common uses of high-voltage transformers include:
- Transportation braking systems
- Manufacturing equipment
- Electrostatic precipitators in waste disposal applications
- Voltage metering and measurement instrumentation
Overall, high-voltage transformers are essential in a large number of industries and applications. They are particularly useful for safely handling voltages of up to 15,000 volts and are critical for the protection of sensitive tools and equipment.
Resources:
- https://www.agilemagco.com/transformers/high-voltage
- https://www.electricityforum.com/td/utility-transformers/high-voltage-transformers
- http://www.studyelectrical.com/2014/03/capacitor-voltage-transformer.html
- https://en.wikipedia.org/wiki/Transformer_types
- https://www.triadmagnetics.com/medical-optics-case-study.html
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