Principles of electromechanical energy conversion

48550 Electrical Energy Technology

Chapter 5. Principles of Electromechanical Energy Conversion
Topics to cover: 1) Introduction 2) EMF in Electromechanical Systems 3) Force and Torque on a Conductor 4) Force and Torque Calculation from Energy and Coenergy 5) Model of Electromechanical Systems

Introduction
For energy conversion between electrical and mechanical forms, electromechanical devices are developed. In general, electromechanical energy conversion devices can be divided into three categories: (1) Transducers (for measurement and control) These devices transform the signals of different forms. Examples are microphones, pickups, and speakers. (2) Force producing devices (linear motion devices) These type of devices produce forces mostly for linear motion drives, such as relays, solenoids (linear actuators), and electromagnets. (3) Continuous energy conversion equipment These devices operate in rotating mode. A device would be known as a generator if it convert mechanical energy into electrical energy, or as a motor if it does the other way around (from electrical to mechanical). Since the permeability of ferromagnetic materials are much larger than the permittivity of dielectric materials, it is more advantageous to use electromagnetic field as the medium for electromechanical energy conversion. As illustrated in the following diagram, an

electromechanical system consists of an electrical subsystem (electric circuits such as windings), a magnetic subsystem (magnetic field in the magnetic cores and airgaps), and a mechanical subsystem (mechanically movable parts such as a plunger in a linear actuator and a rotor in a rotating electrical machine). Voltages and currents are used to describe the

Principle of Electromechanical Energy Conversion

state of the electrical subsystem and they are governed by the basic circuital laws: Ohm's law, KCL and KVL. The state of the mechanical subsystem can be described in terms of positions, velocities, and