Electromechanical Energy Conversion

Today, electrical energy is the most widely used form of energy for performing several industrial, commercial and domestic functions such as pumping water, fans, coolers, air conditioning, refrigeration, etc. Since, most of processes require the conversion of electrical energy into mechanical energy. Also, the mechanical energy is converted into electrical energy. Hence, this clears that we need a mechanism to convert the electrical energy into mechanical energy and mechanical energy into electrical energy and such a mechanism is known as electromechanical energy conversion device.

Electromechanical Energy Conversion Device

Thus, a device which can convert electrical energy into mechanical energy or mechanical energy into electrical energy is known as electromechanical energy conversion device. The electric generators and electric motors are the examples of electromechanical energy conversion device.

In any electromechanical energy conversion device, the conversion of electrical energy into mechanical energy and vice-versa takes place through the medium of an electric field or a magnetic field. Though, in most of the practical electromechanical energy conversion devices, magnetic field is used as the coupling medium between electrical and mechanical systems.

The electromechanical energy conversion devices can be classified into two types −

  • Gross motion devices (like motors and generators)

  • Incremental motion devices (such as electromagnetic relays, measuring instruments, loudspeakers, etc.)

The device which converts electrical energy into mechanical energy is known as electric motor. The device which converts mechanical energy into electrical energy is known as electric generator.

In an electric motor, when a current carrying conductor is placed in a changing (or rotating) magnetic field, the conductor experiences a mechanical force. In case of a generator, when a conductor moves in a magnetic field, an EMF is induced in the conductor. Although, these two electromagnetic effects occur simultaneously, when the energy conversion takes place from electrical to mechanical and vice-versa in all the electromechanical energy conversion devices.

Energy Balance Equation

The energy balance equation is an expression which shows the complete process of energy conversion. In an electromechanical energy conversion device, the total input energy is equal to the sum of three components −

  • Energy dissipated or lost

  • Energy stored

  • Useful output energy

Therefore, for an electric motor, the energy balance equation can be written as,

Electrical energy input = Energy dissipated + Energy stored + Mechanical energy output

Where,

  • The electrical energy input is the electricity supplied from the main supply.

  • Energy stored is equal to sum of the energy stored in the magnetic field and in the mechanical system in the form of potential and kinetic energies.

  • The energy dissipated is equal to sum of energy loss in electric resistance, energy loss in magnetic core (hysteresis loss + eddy current loss) and mechanical losses (windage and friction losses).

For an electric generator, the energy balance equation can be written as,

Mechanical energy input = Electrical energy output + Energy stored + Energy dissipated

Where, the mechanical energy input is the mechanical energy obtained from a turbine, engine, etc. to turn the shaft of the generator.

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