Name the two main core losses in AC machines and their causes.

Name the two main core losses in AC machines and their causes.

• A. Hysteresis loss due to domain switching; eddy current loss due to circulating currents.
• B. Copper loss and dielectric loss.
• C. Radiation loss and mechanical loss.
• D. Thermal loss and windage loss.

Answer: (A)

AC machine cores lose power mainly through two mechanisms tied to a changing magnetic field: hysteresis and eddy currents. Hysteresis loss comes from the realignment of magnetic domains as the magnetic flux in the iron alternates with the AC supply. Each cycle, energy is dissipated as the domains rotate and walls move, so the loss tracks how the material’s B–H loop behaves; materials with narrow, low-coercivity loops reduce this loss and the rate grows with both frequency and flux level. Eddy current loss arises from currents that circulate inside the conducting core whenever the magnetic flux changes. These loops dissipate energy as heat due to the core’s resistivity, and the effect is bigger with higher frequency and larger flux; laminating the core and using higher-resistivity or insulating layers between sheets sharply reduces these circulating currents. The other options point to losses that occur in components like windings (copper loss) or insulation (dielectric loss), or to non-core mechanical or miscellaneous losses, so they don’t describe the main iron losses in the magnetic path.

AC machine cores lose power mainly through two mechanisms tied to a changing magnetic field: hysteresis and eddy currents. Hysteresis loss comes from the realignment of magnetic domains as the magnetic flux in the iron alternates with the AC supply. Each cycle, energy is dissipated as the domains rotate and walls move, so the loss tracks how the material’s B–H loop behaves; materials with narrow, low-coercivity loops reduce this loss and the rate grows with both frequency and flux level. Eddy current loss arises from currents that circulate inside the conducting core whenever the magnetic flux changes. These loops dissipate energy as heat due to the core’s resistivity, and the effect is bigger with higher frequency and larger flux; laminating the core and using higher-resistivity or insulating layers between sheets sharply reduces these circulating currents. The other options point to losses that occur in components like windings (copper loss) or insulation (dielectric loss), or to non-core mechanical or miscellaneous losses, so they don’t describe the main iron losses in the magnetic path.