Core Loss Test
The main source of energy loss in motor is due
to the losses produce in motor during running condition. These losses includes
stator copper loss (I²R),
Stray load loss, windage loss, friction loss and loss in rotor, stator or
armature core. The core loss test is performed to determine the loss in stator
core or armature core. These core losses are divided into hysteresis loss &
eddy current loss. To increase of theses loss result is physically damage or
over heating the core .Due to overheating winding in the stator core is burnt
out or winding insulation failure. Core loss is dissipated in the form of heat
& it further degraded the core ,causing greater core loss and more heat.
This will increase the machine temperature & it will affect the motor efficiency.
Core loop (Flux) test is standard test utilized for evaluating insulation integrity
for lamination of stator core. The test is establishes a specific magnetizing level
for core by energizing the loop coil with single phase power. Any defective
areas of core or core slot or core tooth insulation shows up Hot Spot in that
they will become significantly hotter than surrounding other normal areas. Give
the single phase supply to core as per shown in figure & measure the
temperature of core at particular time interval (up to 30 minute). The final
hot spot temperature difference is not more than 15⁰C
acceptable. If the difference of hot spot is more than 15⁰C [ Note : Some standards ( IEEE 1068 ) require to be within 10⁰C like fan standard efficiency motors.] then rework of stator core is needed & after rework repeat the test until
acceptance criteria met. If same observation is repeated then new stator core
lamination is required.
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ReplyDeleteCan it is useful for small motor?
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