In Case of transformers there were only two types of losses i.e.
constant losses and fixed losses same is true for Induction motors but as
transformer don’t have any rotating part so there were not any mechanical
associated with transformers. But since in motors there is rotating parts so
they have mechanical losses which are also covered in constant losses. Lets
discuss about these losses one by one.

**To know about Transformer losses visit link below:-**

**http://electricalsystembasics.com/2014/04/transformer-losses-efficiency-transformer.html**

__Induction motor losses are divided as below:-__

**1.**

__Constant losses also known as fixed losses__These are known as constant losses as they will remains constant even if induction motor kept running without load. This means that these losses remains fixed irrespective of load on motor. These are further divided as below:-

(a) Core losses known as iron losses

(b) Mechanical losses or Friction losses

**.**

__2__

__Variable losses__These losses are also called copper losses as These losses occur due to current flowing in stator and rotor windings. As the load changes, the current flowing in rotor and stator winding also changes and hence these losses also changes. Therefore these losses are called variable losses. These losses are occurred in both stator and rotor as current flows in both.

(a)
Stator copper losses or Stator ohmic losses

(b)
Rotor copper losses or rotor ohmic losses

(c)
Stray Load losses

Let’s discuss in details about these losses:-

##
__Constant or Fixed Losses__

###
1. Core Losses Or Iron losses

As in case of transformers core losses or iron losses are
further divided into two parts :-

(a)
Hysteresis losses

(b)
Eddy current losses

Eddy current losses can be minimized by using lamination of core.
By laminating the core area decreases and hence resistance increases, which
results in decrease in eddy currents.

Hysteresis losses are minimized by using high grade silicon
steel.

The core losses depend upon frequency.

Stator frequency is always equal to supply frequency and rotor
frequency is equal to slip multiplied by frequency so usually rotor core losses
are very small and can be neglected.

###
2. Mechanical losses or Friction
losses

Mechanical losses occur at the bearing and brush friction loss
occurs in wound rotor induction motor. These losses vary slightly with the
change in speed.

Fixed losses = Power I/P at no load- Stator I

^{2}R loss at no load##
__Variable Losses:-__

The copper losses or Ohmic losses are obtained by performing
blocked rotor test on three phase induction motor. The stator and rotor ohmic
losses or copper losses can be calculated directly if stator and rotor winding
losses are known.

Stray load losses occur in iron as well as in conductors. They
are usually taken as 0.5% of motor efficiency.

__Power flow diagram for 3-phase induction motor is given below:-__
Power flow diagram has shown how these losses takes place during
conversion of electrical power to mechanical power. Under normal running
conditions rotor core losses are neglected.
Power developed at shaft differs from mechanical power developed by
friction and windage losses.