Electric motors are devices, which utilize magnetic fields and current-carrying conductors to establish movements in machines (Brian, 2011). Electric motors are installed with magnetic objects, which when they interact with the current-carrying conducts, they produce a force, which makes a machine to move or start functioning. The force produced by electric motors is in a form of electrical energy, which is produced through the reverse process from mechanical energy (Brian, 2011). Generators perform the reverse process of producing electrical energy in electric motors. Examples of generators found in electric motors include dynamo, and alternator.
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Electric motors are found in home appliances such as refrigerators and televisions, in the disk drives of computers, and in industrial machines such as fans, powers tools, and blowers. Uses of electric motors range from small devices such as an electric wristwatch to large devices such as ships. These machines make use of portable power devices like batteries or power-carrying devices that are internally constructed, and which interchange currents from a central electrical distribution system (Brian, 2011).
Principles utilized by electric motors in production of electrical energy include the principle of electrostatics, principle of magnetism, and principle of piezoelectric (Brain, 2011). The principle of magnetism is the common used. Under this principle, two magnetic fields: the stator and the rotor are used to produce energy. The stator and the rotor interact with each other to produce a force, which twists/turns the drive/motor shaft in an electric motor or any other electric device. For movement to occur, one of the magnetic fields: the stator or the rotor must change once the turning force is released into the drive/motor shaft (Brain, 2011). Variation in either of the magnetic fields can be achieved by either switching on and off the magnetic poles, or by adjusting the strength of of the poles from time to time (Brain, 2011).
Usually, electric motors use control systems to regulate their movements. Control systems regulate the functioning on other systems or devices. Types of control systems include linear control systems, and logic control systems (Electric Drives - Motor Controllers and Control Systems, 2005). Linear control systems make use of the feedback mechanism to control movements in devices/machines. Whilst using feedback mechanism, a control system has its operating devices, which include a control loop, a sensor, an activator, and an actuator, arranged in a way that they regulate the operations of a machine when certain pre-set conditions occur (Electric Drives - Motor Controllers and Control Systems, 2005). For example, in an oil refining company, linear control systems may be set in such a manner that, the speed of pumping refined oil from the refinery to the storage tanks increases as the refinery’s temperatures decreases, and decreases as the refinery’s temperature increases. In some cases, linear control systems use negative feedback to regulate functioning of mechanical/electrical devices. Such systems use thermostat to control functioning of devices. For instance, a heater switches off when pre-set maximum temperatures are attained and switches-on after the temperatures go down up-to a pre-set minimum point.
On the other hand, logic control systems utilize inbuilt microcontrollers or programmable logic controllers to regulate functioning of devices (Electric Drives - Motor Controllers and Control Systems, 2005). In many cases, logic control systems act in response of actions of switches, and sensors. Response to such actions either causes the device to stop or start various functions. Good examples of such devices that utilize logic control systems are; elevators, x-ray machines, and washing machines.
Currently, a new control system: fuzzy logic which, utilizes both the features of logic control and linear control system, is in use. Fuzzy logic combines simply designed logic controllers with linear controllers to regulate functioning of various devices (Electric Drives - Motor Controllers and Control Systems, 2005). Measurement, which range between zero and one, characterize the functioning of fuzzy logic. A measurement of one indicates yes, while a measurement of zero indicates no. Rules regulating the operation of devices are first written in normal language, and then decoded into fuzzy logic: measurements between zero and one. Fuzzy logic then utilizes Boolean arithmetic to make representation of various operations in a device. The values of Boolean arithmetic are usually between zero and one. Lastly, a device installed with fuzzy logic makes use of the values generated by arithmetically represented operations to undertake its operations (Electric Drives - Motor Controllers and Control Systems, 2005).