ENGINEERING PROJECT

DC machines are one of the most commonly used machines for electromechanical energy conversion. Converters which are used continuously to convert electrical input to mechanical output or vice versa are called electric machines. An electric machine is therefore a link between an electrical system and a mechanical system. In these machines, the conversion is reversible. If the conversion is from mechanical to electrical, the machine is said to act as a generator. If the conversion is from electrical to mechanical, the machine is said to act as a motor. Therefore, the same electric machine can be made to operate as a generator as well as a motor.[2]

DC machines may also work as brakes. The brake mode is a generator action but with the electrical power either regenerated or dissipated within the machine system, thus developing a mechanical braking effect. It also converts some electrical or mechanical energy to heat, but this is undesired.

The major advantages of DC machines are easy speed and torque regulation. The major parts of any machine are the stationary component called the stator and the rotating component is called the rotor.

At the most basic level, electric motors exist to convert electrical energy into mechanical energy. Electric motors exist to convert electrical energy into mechanical energy. This is done by two interacting magnetic fields that is one stationary and another attached to a part that can move. DC motors have the potential for very high torque capabilities (depands on motor size), are easy to miniaturize, and can be "throttled" via adjusting their supply voltage. DC motors are also not only the simplest, but the oldest electric motors.

1) Michael Faraday (U.K.)[1]

Fabled experimenter Michael Faraday decided to confirm or refute a number of speculations surrounding Oersted's and Ampere's results. Faraday set to work devising an experiment to demonstrate whether or not a current carrying wire produced a circular magnetic field around it, and in October of 1821 succeeded in demonstrating this.

Faraday took a dish of mercury and placed a fixed magnet in the middle; above this, he dangled a freely moving wire (the free end of the wire was long enough to dip into the mercury). When he connected a battery to forn a circuit, the current carrying wire circled around the magnet. Faraday then reversed the setup, this time with a fixed wire and a dangling magnet and again the free part circled around the fixed part. This was the first demonstration of the conversion of electrical energy into motion. As a result, Faraday is often credited with the invention of the electric motor. Bear in mind, though, that Faraday's electric motor is really just a lab demonstration, as you can't harness it for useful work.

2) Joseph Henry (U.S.)[1]

It took ten years, but by the summer of 1831 Joseph Henry had improved on Faraday's experimental motor. Henry built a simple device whose moving part was a straight electromagnet rocking on a horizontal axis. Its polarity was reversed automatically by its motion as pairs of wires projecting from its ends made connections alternately with two electrochemical cells. Two vertical permanent magnets alternately attracted and repelled the ends of the electromagnet, making it rock back and forth at 75 cycles per minute.

Henry considered his little machine to be merely a "philosophical toy," but nevertheless believed it was important as the first demonstration of continuous motion produced by magnetic attraction and repulsion. While being more mechanically useful than Faraday's motor, and being the first real use of electromagnets in a motor, it was still by and large a lab experiment.

3) William Sturgeon (U.K.)[1]

Just a year after Henry's motor was demonstrated, William Sturgeon invented the commutator, and with it the first rotary electric motor in many ways a rotary analogue of Henry's oscillating motor. Sturgeon's motor, while still simple, was the first to provide continuous rotary motion and contained essentially all the elements of a modern DC motor. Note that Sturgeon used horseshoe electromagnets to produce both the moving and stationary magnetic fields (to be specific, he built a shunt wound DC motor).

Electric machines play an important role in industry as well as our daily life. They are used to generate electrical power in power plants and provide mechanical work in industries. They are also an indispensable part of our daily lives. Electric machines are very important pieces of equipment in our everyday lives. The DC machine is considered to be basic electric machines.

The aim of this thesis is to introduce the modelling of power components and to use computer simulation as a tool for conducting transient and control studies. Simulation can be very helpful in gaining insights to the dynamic behaviour and interactions that are often not readily apparent from reading theory. To having an actual system to experiment on simulation is often chosen by engineers to study transient and control performance or to test conceptual designs.

MATLAB software is used because of the short learning curve that most students require to start using it for wide distribution and general purpose nature. This will demonstrate the advantages of using MATLAB for analysing power system steady state behaviour and its capabilities for simulating transients in power systems and power electronics including control system dynamic behaviour.