Electromechanical Energy Conversion Principles

An electromechanical energy conversion device is the device that converts electrical energy into mechanical energy or, mechanical energy into electrical energy. Electromechanical energy conversion takes place via the medium of a magnetic field or an electric field, but most practical converters use magnetic field as the coupling medium between electrical and mechanical systems, this is because the electric storing capacity of the magnetic field is much higher than that of the electric field. Electromechanical energy converters are either gross-motion devices such as microphones, loudspeakers, electromagnetic relays, and certain electrical measuring instruments, etc.

DC, induction and synchronous machines are used extensively for electromechanical energy conversion. When the conversion takes place from electrical to mechanical form, the device is called the motor, and when the mechanical energy is converted to electrical energy, the device is called a generator. In these machines, conversion of energy from electrical to mechanical form or from mechanical to electrical from results from the following two electromagnetic phenomena:

1. When a conductor is allowed to move in a magnetic field, a voltage is induced in the conductor.
2. When a current-carrying conductor is placed in a magnetic field, then a mechanical force is experienced by the conductor.

In monitoring action, current flows through the conductors placed in a magnetic field. A force is produced on each conductor. The conductors are placed on the rotor which is free to move. An electromagnetic torque produced on the rotor is transferred to the shaft of the rotor and can be utilized to drive a mechanical load. Since the conductors rotate in the magnetic field, a voltage is induced in each conductor. In generating action, the rotor is driven by a prime mover. A voltage is induced in the rotor conductors. If an electrical load is connected to the winding formed by these conductors, a current will flow, delivering electric power to the load. Moreover, the current flowing through the conductors will interact with the magnetic field to produce a reaction torque, which will tend to oppose the torque developed by the prime mover.

Conservation of energy

According to the principle of conservation of energy, energy can neither be created nor be destroyed it can only be transformed from one state to another.

In an energy conversion device, the total input energy is equal to the sum of the following three components:

Thus, with an electromechanical conversion device, the energy balance equation can be written as

The above equation is for motor action. For generator action, the energy balance equation is written as