Law of Conservation of Energy

Definition: The law of conservation of energy states that the energy can neither be generated nor destroyed. It is converted from one form to another. The total input power is equal to the sum of the following three components; they are the dissipated energy, stored energy and useful output energy.The devices which convert the mechanical energy into electrical energy and electrical energy into mechanical energy is called an electromechanical device

The energy conversion takes place via the medium of an electrical and magnetic field. When the conversion takes place from electrical energy to mechanical energy, then the device is called motor. When the mechanical energy is converted into electrical energy, the device is known as a generator. The conversion of energy takes place from following two electromagnetic phenomena.

  1. When the current carrying conductor moves in a magnetic field, the voltage induces in the conductor.
  2. When a current carrying conductor placed in a magnetic field, the conductor experiences a magnetic field.

Usually, the converter uses a magnetic field as a coupling medium between the electric and magnetic system because their energy storing capacity is much greater than that of the electric field.

The energy balance equation for motor action is given as

motor-equationIn motor action, the electric power is taken as the input from the main supply. The mechanical energy obtained from the output is not fully utilised. The fraction of the energy is dissipated in frictional losses (friction and windage).

For generator action, the energy balance equation is written as

generator-equationThe total energy stored in any electromechanical devices is equal to the sum of the energy stored in the magnetic field, the energy stored in the mechanical system, and potential or kinetic energy.

The energy dissipated in an electric circuit is equal to the sum of the energy dissipated in an electrical circuit as an ohmic loss, energy dissipated in a magnetic circuit as hysteresis and eddy current losses and the energy consumed in the mechanical system as friction and windage loss, etc.

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