Power electronics

A battery charger is an example of a power electronic piece

The expression power electronics is used to differentiate the type of application given to electronic devices, in this case to transform and control voltages and currents of significant levels. This type of application is thus differentiated from other electronic applications called low power or also weak and strong currents.

In this type of application, electricity and electronics meet again, since the control that electronic circuits allow is used to control the conduction (on and off) of power semiconductors to manage currents and voltages in power applications. This by forming equipment called static power converters.

In this way, power electronics allows adapting and transforming electrical energy for different purposes such as powering other equipment in a controlled manner, transforming electrical energy from direct to alternating or vice versa, and controlling the speed and operation of electrical machines, etc. through the use of electronic devices, mainly semiconductors. This includes both applications in control systems, power factor and/or harmonic compensation systems, as well as for power supply to industrial consumers or even the interconnection of electrical power systems of different frequencies.

The main objective of this discipline is the management and transformation of energy in an efficient way, thus avoiding the use of resistive elements, potential generators of losses due to the Joule effect. The main devices used therefore are coils and capacitors, as well as semiconductors working in cut/saturation mode (on/off, on and off).

Power semiconductor devices

For these applications, a series of power semiconductor devices have been developed, which are derived from the diode or transistor. Among these are the following:

• Silicone Controller (SCR)
• Triac
• IGBT Transistor, acronym for Insulated Gate Bipolar Transistor, Bipolar Transistor with insulated gate
• Tiristor GTO, acronym for Gated Turnoff Thyristor, Tiristor off by gate
• Tiristor IGCT, acronym for Insulated Gate Controlled Thyristor, Tiristor controlled by gate
• Tiristor MCT, acronym for MOS Controlled Thyristor

Electric power converters

Power conversion is the process of converting one form of energy into another, this can include electromechanical or electrochemical processes.

These devices are used in equipment called static power converters, classified as:

• Rectifiers: convert alternating current into continuous current
• Investors: convert continuous current into alternating current
• Cycloconversions: convert alternating current into alternating current of another smaller frequency
• Choppers: convert continuous current into lower or higher voltage

Currently this discipline is gaining more and more importance mainly due to the high efficiency of electronic converters compared to traditional methods, and their greater versatility. An essential step for this revolution to take place was the development of devices capable of handling the high powers required for electrical distribution tasks or handling powerful motors.

Applications

The main applications of power electronic converters are the following:

• Food sources: At present, a subtype of electronic power sources, known as switched power sources, have become very important. These sources are characterized by their high performance and reduced volume. The clearest example of application is found in the power supply of computers.
• Electric motor control: The use of electronic converters allows to control parameters such as position, speed or pair supplied by an engine. This type of control is currently used in air conditioning systems. This technique, called commercially "inverter" replaces the old on/off control by a speed regulation that saves energy. It has also been widely used in rail traction, mainly in vehicles suitable for continuous current (C.C.) during the 1970s and 1980s, as it allows to adjust energy consumption to the actual requirements of the traction engine, in contrast to the consumption of vehicles controlled by start-up and braking resistances. Currently the chopper system is still valid, but it is no longer used in the manufacture of new vehicles, as equipment based on the triphase engine is currently used, much more powerful and reliable than the collector engine.
• Induction heating: It consists of heating a conductor material through the field generated by an inducer. Inducer feeding is done at high frequency, usually in the kHz range, so that electronic frequency converters are required. The most visible application is found in the current induction kitchens.
• Others: As discussed above are countless applications of power electronics. In addition to those already mentioned, they highlight: uninterrupted feeding systems, power factor control systems, electronic bullets for high-frequency illumination, interface between renewable energy sources and the electricity grid, etc.

Current lines of research seek the integration of power and control devices in a single chip, reducing costs and multiplying their potential applications. However, there are difficulties to overcome such as the isolation between zones working at high voltages and control circuitry, as well as the dissipation of lost power.