E283C1 - EEEB344 Electromechanical Devices Chapter 1...

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EEEB344 Electromechanical Devices Chapter 1 CHAPTER 1 – Introduction to Machinery Principles Summary: 1. Basic concept of electrical machines fundamentals: o Rotational component measurements Angular Velocity, Acceleration Torque, Work, Power Newton’s Law of Rotation o Magnetic Field study Production of a Magnetic Field Magnetic Circuits 2. Magnetic Behaviour of Ferromagnetic Materials 3. How magnetic field can affect its surroundings: Faraday’s Law – Induced Voltage from a Time-Changing Magnetic Field. Production of Induced Force on a Wire. Induced Voltage on a Conductor moving in a Magnetic Field 4. Linear DC Machines 1
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EEEB344 Electromechanical Devices Chapter 1 Introduction 1. Electric Machines mechanical energy to electric energy or vice versa Mechanical energy Electric energy : GENERATOR Electric energy mechanical energy : MOTOR 2. Almost all practical motors and generators convert energy from one form to another through the action of a magnetic field . 3. Only machines using magnetic fields to perform such conversions will be considered in this course. 4. When we talk about machines, another related device is the transformer. A transformer is a device that converts ac electric energy at one voltage level to ac electric energy at another voltage level. 5. Transformers are usually studied together with generators and motors because they operate on the same principle, the difference is just in the action of a magnetic field to accomplish the change in voltage level. 6. Why are electric motors and generators so common? - electric power is a clean and efficient energy source that is very easy to transmit over long distances and easy to control. - Does not require constant ventilation and fuel (compare to internal-combustion engine), free from pollutant associated with combustion 1. Basic concept of electrical machines fundamentals 1.1 Rotational Motion, Newton’s Law and Power Relationship Almost all electric machines rotate about an axis , called the shaft of the machines. It is important to have a basic understanding of rotational motion. Angular position, θ - is the angle at which it is oriented, measured from some arbitrary reference point. Its measurement units are in radians (rad) or in degrees. It is similar to the linear concept of distance along a line. Conventional notation: +ve value for anticlockwise rotation -ve value for clockwise rotation Angular Velocity, ϖ - Defined as the velocity at which the measured point is moving. Similar to the concept of standard velocity where: dr v dt = where: r – distance traverse by the body t – time taken to travel the distance r For a rotating body, angular velocity is formulated as: d dt θ ϖ = (rad/s) where: θ - Angular position/ angular distance traversed by the rotating body 2
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EEEB344 Electromechanical Devices Chapter 1 t – time taken for the rotating body to traverse the specified distance, ϑ . Angular acceleration,
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This note was uploaded on 03/03/2010 for the course POWER 332 taught by Professor Dr during the Spring '10 term at Ain Shams University.

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E283C1 - EEEB344 Electromechanical Devices Chapter 1...

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