Lecturer:

Building Electrical Systems

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Lecturer:

Transformers

Different types of transformers are to serve on different purposes. Despite this difference in design, they use the same principle in power supply in conversion of low voltage to high voltage using the Michael Faraday principle in 1831. In power supply system, different types of transformers serve different functions, which in turn has led to categorizing the transformers in different types:

  1. Power transformers:

  1. Laminated core transformers is the most common transformer type used in appliances and power transmission in converting the mains voltage to low voltage used in powering electronic devices.

  2. Variable autotransformer, this transformer has a part of the winding coils exposed and has a sliding carbon brush used for secondary connection. When the autotransformer has variable turn ratio that are nearly continuous, it allows for adjustment for voltage in small bits (Herman, 2011, p.623).

  3. Leakage transformers, these transformers have a higher inductance leakage compared to other transformers, which is sometimes increased by magnetic shunt between the secondary and the primary core and it is adjustable using a setscrew. Mostly these transformers are used in arc welding and lamps that use discharge voltage. This way leakage transformer acts like a magnetic ballast and as a voltage transformer.

  4. Isolating transformer, this type of transformer connects two circuits magnetically, but does not provide metallic conductive path between any given two circuits. An example of application is in the medical equipment to prevent leakage into the devices from the AC supply.

  1. Instrument Transformer: — these transformers are typically used in operation of instruments with voltage lines or circuits with high current, isolating measurement safely and circuitry control from high currents and voltages.

  2. Current transformer, this is a measurement device connected in series to provide a proportional secondary current to the primary current (Cogdell, 1999, 76). These type of transformers are commonly used in protective relays and metering in electrical power industry. Often the current transformers are constructed by passing an insulated cable or a bus bar through a toroidal core that is well insulated and wrapped with wire turns.

  3. Voltage transformer, which is also called potential transformer and are used in high voltage protection and metering or isolation phasor phase shift. Their design presents negligible load supplying accurate voltage ratio enabling metering that is accurate. Voltage transformers are classified into three main types: optical, capacitor and electromagnetic.

Motors are broadly classified into two main types, AC motors and DC motors.

DC motors: In the contemporary engineering practice DC power systems are not very common. However, for years DC motors coupled with DC drive, they provide exact control of conveyors, extruders, material handling, extruders, portable electronics, aircraft and other applications that need speed control.

AC Motors:

An AC motor has two main parts the rotor connected to the shaft that serve as the output and stator, which has coils that produce electromagnetic field produce by the alternating current connected to the coils.

Mainly there are two types, induction motors and synchronous.

Induction or asynchronous motors mainly rely on difference between the rotating magnetic field and the rotating shaft known as slip for operation. While the synchronous motor does not rely on the induced slip operate, instead it uses salient poles, permanent magnets or rotor winding that is independently excited (Zorbas, 2014, p.621).

There are other types of motors, which include, eddy current motors

References

Herman, L., 2011, Electrical Transformers and Rotating Machines, Cengage Learning, New York.

Cogdell, J. R., 1999, Foundations of Electric Power, Prentice Hall, New Jersey.

Zorbas, D., 2014, Electric Machines: Principles, Applications, and Control Schematics, Cengage Learning, New York.