We have already discussed
about losses in electrical machine in “Losses in Electrical Machine - Core Loss”. Under normal operating condition, the
core loss in the Rotor of an Induction Motor is negligible. In this post we
will discuss about this.

Core loss consists of Hysteresis
Loss and Eddy Current Loss. Hysteresis Loss is directly proportional to

**B**and Eddy current loss is directly proportional to^{x}f**B**. At standstill condition the frequency of induced emf is equal to the source frequency connected to the stator of induction motor but as the motor speeds up, the rotor frequency decreases and at a slip s, the frequency of rotor emf becomes^{2}f^{2}**sf**.
As the slip of induction
motor is near to zero i.e. of the order of 0.02, hence the frequency of rotor
will be 0.02x50 Hz = 1 Hz (Assuming the supply frequency of 50 Hz). Thus we see
that under normal operating condition the frequency of rotor is very small and therefore
the corresponding Hysteresis and Eddy current Loss will also be less.

That is why under normal
operating condition the rotor core loss of Induction Motor is negligible.

Thank you!

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