PRINCIPLE OF ENERGY CONVERSION
When energy is converted from one form into another, the principle of conversion of energy can be
invoked. According to this principle, energy can neither be created nor destroyed, it can merely be
converted from one form into another.
In energy conversion devices, out of the total input energy, some energy is converted into the
required form, some energy is stored and the rest is dissipated. In view of this, the energy balance
equation must include these four energy terms and for a motor, it can be written as
(Total electrical energy input) = (Mechanical energy output) + (Total energy stored) + (Total energy
dissipated)
The principle of energy conversion is based on the energy balance in the above equation. It should
be noted that the below equation is written for motor action where electrical energy input and
mechanical energy output are treated as positive terms. For generator action,
(Total mechanical energy input) = (Electrical energy output) + (Total energy stored) + (total energy
dissipated)
The various forms of energies involved in equation two for an electromechanical energy conversion
device are now described below:
(i) Total electrical energy input from the supply mains is Wei.
(ii) The mechanical energy output is Wmo.
(iii) Total energy stored in any device = Energy stored in a magnetic field, Wes + Energy
stored in a mechanical system, Wms.
(iv) Total energy dissipated = Energy dissipated in electric as ohmic losses + Energy
dissipated as magnetic core loss (hysteresis and eddy-current losses) + Energy dissipated
in mechanical system (friction and windage losses etc.)
Thus, the energy balance equation 1 can be written in more specific terms as
Wei = Wmo + (Wes + Wms) + (Ohmic energy losses + Coupling field energy losses) + (Energy losses in
mechanical system.)
The subscripts e, m, s and o stand for electrical, mechanical, input, stored and output respectively.
For example, subscript ei denotes electrical input (energy), subscripts ms denote mechanical stored
(energy).
If the appropriate terms are grouped together, then the energy balance equation becomes,
(Wei – Ohmic energy losses) = (Wmo + Wms + Mechanical energy losses) + (Wes + Coupling field
energy losses)
Welec = Wmech + Wfld
Or
Equation leads to the electromechanical energy conversion model of below Fig. the various losses,
i.e. I²R losses, coupling field losses and the friction and windage losses are irreversible, and these are
therefore dissipated as heat. Energy stored in the coupling field Wes’ is dealt with later Art. The
energy stored in the mechanical system Wms’ is the kinetic energy 1/2.
When energy is converted from one form into another, the principle of conversion of energy can be
invoked. According to this principle, energy can neither be created nor destroyed, it can merely be
converted from one form into another.
In energy conversion devices, out of the total input energy, some energy is converted into the
required form, some energy is stored and the rest is dissipated. In view of this, the energy balance
equation must include these four energy terms and for a motor, it can be written as
(Total electrical energy input) = (Mechanical energy output) + (Total energy stored) + (Total energy
dissipated)
The principle of energy conversion is based on the energy balance in the above equation. It should
be noted that the below equation is written for motor action where electrical energy input and
mechanical energy output are treated as positive terms. For generator action,
(Total mechanical energy input) = (Electrical energy output) + (Total energy stored) + (total energy
dissipated)
The various forms of energies involved in equation two for an electromechanical energy conversion
device are now described below:
(i) Total electrical energy input from the supply mains is Wei.
(ii) The mechanical energy output is Wmo.
(iii) Total energy stored in any device = Energy stored in a magnetic field, Wes + Energy
stored in a mechanical system, Wms.
(iv) Total energy dissipated = Energy dissipated in electric as ohmic losses + Energy
dissipated as magnetic core loss (hysteresis and eddy-current losses) + Energy dissipated
in mechanical system (friction and windage losses etc.)
Thus, the energy balance equation 1 can be written in more specific terms as
Wei = Wmo + (Wes + Wms) + (Ohmic energy losses + Coupling field energy losses) + (Energy losses in
mechanical system.)
The subscripts e, m, s and o stand for electrical, mechanical, input, stored and output respectively.
For example, subscript ei denotes electrical input (energy), subscripts ms denote mechanical stored
(energy).
If the appropriate terms are grouped together, then the energy balance equation becomes,
(Wei – Ohmic energy losses) = (Wmo + Wms + Mechanical energy losses) + (Wes + Coupling field
energy losses)
Welec = Wmech + Wfld
Or
Equation leads to the electromechanical energy conversion model of below Fig. the various losses,
i.e. I²R losses, coupling field losses and the friction and windage losses are irreversible, and these are
therefore dissipated as heat. Energy stored in the coupling field Wes’ is dealt with later Art. The
energy stored in the mechanical system Wms’ is the kinetic energy 1/2.
