Chapter 2. Electromechanical Energy Conversion

[Pages:60]Chapter 2.

Electromechanical Energy Conversion

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Introduction

Electromechanical energy conversions ? use a magnetic field as the medium of energy conversion

Electromechanical energy conversion device: Converts electrical energy into mechanical energy

or Converts mechanical energy into electrical energy.

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Introduction

Three categories of electromechanical energy conversion devices:

Transducers (for measurement and control)- small motion

Transform the signals of different forms. Examples: microphones, sensors and speakers.

Force producing devices (translational force)- limited mechanical motion.

Produce forces mostly for linear motion drives, Example Actuators - relays, solenoids and electromagnets.

Continuous energy conversion equipment.

Operate in rotating mode. Examples: motors and generators.

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Energy Conversion Process

The principle of conservation of energy:

Energy can neither be created nor destroyed. It can only be changed from one form to another. Therefore total energy in a system is constant

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Energy Conversion Process

An electromechanical converter system has three essential parts:

An electrical system (electric circuits such as windings) A magnetic system (magnetic field in the magnetic cores and air gaps) A mechanical system (mechanically movable parts such as a rotor in an

electrical machine).

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EM Energy Conversion: Analogy

Electrical Energy (input)

Thermal Energy (losses)

Field Energy

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Mechanical Energy (output)

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Energy Conversion Process

Electrical System

Electromechanical System

Magnetic System

Mechanical System

Voltages and Currents

Magnetic Flux

Position, Speed and Acceleration

Circuit Equations (KVL and KCL)

emf

Froce/Torque

Force/Torque Eqns (Newtons Law)

Concept of electromechanical system modeling

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Energy Conversion Process

Electrical system

Magnetic system

Mechanical system

P mech

Electrical loss

Field loss

Mechanical loss

The energy transfer equation is as follows:

Electrical energy input from sources

Mechanical energy output

Increase in stored energy in magnetic field

Energy losses

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