UNIT - 3 LOSSES AND EFFICIENCY OF DC MACHINES: It is convenient to determine the efficiency of a rotating machine by determining the losses than by direct loading. Further it is not possible to arrange actual load for large and medium sized machines. By knowing the losses, the machine efficiency can be found by = (For generators) 1 ……… = (For motors) 2 …………… In the process of energy conversion in rotating machines - current, flux and rotation are involved which cause losses in conductors, ferromagnetic materials and mechanical losses respectively. Various losses occurring in a DC machine are listed below. Total losses can be broadly divided into two types. Constant losses Variable losses losses can be further divided as Constant losses i) Core loss or iron loss – Hysteresis loss Eddy current loss ii) Mechanical loss Windage loss Friction loss friction loss and Bearing friction loss. – Variable losses i) copper loss ( ) – Armature copper loss copper loss
UNIT - 3 LOSSES AND EFFICIENCY OF DC MACHINES: It is convenient to determine the efficiency of a rotating machine by determining the losses than by direct loading. Further it is not possible to arrange actual load for large and medium sized machines. By knowing the losses, the machine efficiency can be found by = (For generators) ……… 1 = (For motors) …………… 2 In the process of energy conversion in rotating machines - current, flux and rotation are involved which cause losses in conductors, ferromagnetic materials and mechanical losses respectively. Various losses occurring in a DC machine are listed below. Total losses can be broadly divided into two types. Constant losses Variable losses losses can be further divided as Constant losses – i) Core loss or iron loss Hysteresis loss Eddy current loss ii) Mechanical loss Windage loss Friction loss – friction loss and Bearing friction loss. Variable losses – i) copper loss ( ) Armature copper loss copper loss
U3-L17_-LOSSES-OF-DC-MACHINES.docx