ELECTROMECHANICAL ENERGY CONVERSION PRINCIPLES
Conversion of other forms of energy into electrical energy is a common practice. The main
advantage of this conversion is that energy in electrical form can be transmitted, utilized, and
controlled more easily, reliably, and efficiently. Energy conversion devices are required first for
converting other forms of energy into electrical energy and then for converting electrical energy into
required useful forms, such as sound, light, heat, or mechanical energy. In other words, energy
conversion devices are required at both ends of an electrical system, since energy is neither available
nor required in electrical form. One typical example illustrating the processing of energy is a
hydroelectric plant where energy is converted to electrical form. It is then transmitted and
distributed over lines and finally converted to mechanical energy in an electric motor for final use.
Another example is the conversion of sound energy into electrical energy at the talker’s end, its
transmission over lines in electrical form, and its final conversion to sound waves at the listener’s
end.
An electromechanical energy conversion device is one that converts electrical energy into
mechanical energy or mechanical energy into electrical energy. The operating principles of energy
conversion devices are similar, but their structural details differ depending upon their function.
Various electromechanical energy conversion devices may be categorized as under:
(i) The first category of devices, involving small motion, processes only low-energy signals
from electrical to mechanical or vice versa. These include telephone receivers,
loudspeakers, microphones, gramophone pick-ups, and low-signal transducers.
(ii) The second category consists of force-, or, torque-producing devices with limited
mechanical motion. Examples of such devices are electromagnets, relays, moving-iron
instruments, moving-coil instruments, actuators, etc.
(iii) The third category includes continuous energy conversion devices like motors and
generators, these are used for bulk energy conversion and utilization. In a machine
acting as a motor, energy is converted from electrical to mechanical, whereas in a
generator, energy is converted from mechanical to electrical.
The energy conversion process is basically a reversible process. However, in practice, devices may be
designed and constructed to suit one particular mode of conversion or the other.
All these energy conversion devices operate on similar physical principles, but their constructional
details differ. The coupling between the electrical and mechanical systems of these devices is
through the magnetic or electric field. The object of this chapter is to develop the
electromechanical-energy conversion principles with field energy as the basis. The analysis of energy
conversion devices by field-energy concept is more general and broad-based since it is applicable to
all devices possessing rotational, linear, or vibratory motions. Other advantages of this approach are
as follows:
(i) It can deal with both steady-state and transient analysis of all electromechanical energy
converts.
(ii) It gives more physical insight into the operation of all these devices, which is
indispensable.
(iii) This approach leads physically to the generalized theory of electrical machines.
(iv) The conventional approach can be introduced at any stage, to study the effect of
saturation, commutation, etc.
Conversion of other forms of energy into electrical energy is a common practice. The main
advantage of this conversion is that energy in electrical form can be transmitted, utilized, and
controlled more easily, reliably, and efficiently. Energy conversion devices are required first for
converting other forms of energy into electrical energy and then for converting electrical energy into
required useful forms, such as sound, light, heat, or mechanical energy. In other words, energy
conversion devices are required at both ends of an electrical system, since energy is neither available
nor required in electrical form. One typical example illustrating the processing of energy is a
hydroelectric plant where energy is converted to electrical form. It is then transmitted and
distributed over lines and finally converted to mechanical energy in an electric motor for final use.
Another example is the conversion of sound energy into electrical energy at the talker’s end, its
transmission over lines in electrical form, and its final conversion to sound waves at the listener’s
end.
An electromechanical energy conversion device is one that converts electrical energy into
mechanical energy or mechanical energy into electrical energy. The operating principles of energy
conversion devices are similar, but their structural details differ depending upon their function.
Various electromechanical energy conversion devices may be categorized as under:
(i) The first category of devices, involving small motion, processes only low-energy signals
from electrical to mechanical or vice versa. These include telephone receivers,
loudspeakers, microphones, gramophone pick-ups, and low-signal transducers.
(ii) The second category consists of force-, or, torque-producing devices with limited
mechanical motion. Examples of such devices are electromagnets, relays, moving-iron
instruments, moving-coil instruments, actuators, etc.
(iii) The third category includes continuous energy conversion devices like motors and
generators, these are used for bulk energy conversion and utilization. In a machine
acting as a motor, energy is converted from electrical to mechanical, whereas in a
generator, energy is converted from mechanical to electrical.
The energy conversion process is basically a reversible process. However, in practice, devices may be
designed and constructed to suit one particular mode of conversion or the other.
All these energy conversion devices operate on similar physical principles, but their constructional
details differ. The coupling between the electrical and mechanical systems of these devices is
through the magnetic or electric field. The object of this chapter is to develop the
electromechanical-energy conversion principles with field energy as the basis. The analysis of energy
conversion devices by field-energy concept is more general and broad-based since it is applicable to
all devices possessing rotational, linear, or vibratory motions. Other advantages of this approach are
as follows:
(i) It can deal with both steady-state and transient analysis of all electromechanical energy
converts.
(ii) It gives more physical insight into the operation of all these devices, which is
indispensable.
(iii) This approach leads physically to the generalized theory of electrical machines.
(iv) The conventional approach can be introduced at any stage, to study the effect of
saturation, commutation, etc.
