What is difference between eddy current loss and hysterisis loss?

Answer 1

Whenever rotor cuts the magnetic field, emf is induced it. Due to this emf, some current may flow in the rotor. This current is called Eddy current which is unnecessary and considered a loss called Eddy current loss.

When a magnetic material is energised it follows B-H curve and when de-energised, it does not follow B-H curve. This difference is considered a loss called Hysterisis loss.

Answer 2

'Hysteresis' comes from a Greek word, meaning 'to lag'. In this context, it describes the way in which changes in the flux density (B) in a transformer's core lags behind changes in the magnetic field strength (H) that causes it. The cross-sectional area of what is known as a 'hysteresis loop' (a graph plotted of B against H, over a complete cycle of a.c.) represents the amount of energy required to magnetise and demagnetise the core. These hysteresis losses represent energy losses within the core, and is a function of the type of material used in the manufacture of the core.

'Eddy current' losses are energy losses (I2Rt) caused by circulating currents set up within the core due to voltages induced into that core. These can be minimised by manufacturing the transformer's core from insulated laminations, rather than a solid core.

Answer 3

'Eddy currents' are circulating currents within the core of a machine, such as a transformer, due to voltages induced into that core due to a fluctuating magnetic field. These currents act to raise the temperature of the core, causes energy losses to the surroundings by heat transfer.

'Hysteresis' losses are due to the energy required to alternately magnetise and demagnetise the core as the magnetising current alternates. This energy represents a loss.