In order to study operating characteristics of three phase squirrel cage induction motor, we need to assume that the motor started with no-load on the same. No load on the motor includes the following points:
Reactions of motor at no load speed
Few reactions are observed when the motor is sustained at no load speed and the value of slip to be conveyed at the lower percent a 0.1. Let’s discuss those reactions in detail:
At first, the speed of the motor will decrease followed by the increasing value of slip. The slip value is increased because of the rotor bars realizes some cuts because of the synchronous speed continued with stator fields. Induced electromotive force is then increased because as a result of the constant cutting of rotor bards which increases the current in the rotor bars.
The reaction will then follow to torque which is developed because of the increasing rotor till the time it can carry the load on the motor which is placed. And the torque will consequently develop when the motor will continue to rotate at that particular slip place at a particular load.
When does torque reach the break down situation?
As the process continues, the motor will stop when additional load will be placed on the same after reaching the break down value of torque. When the normal range operation of the three phase squirrel induction motor is disturbed beyond, the break down value of torque is noticed.
It is also stated that the induction motor can adjust itself as per the torque applied to the motor which is similar to the operation of shunt motor. The statement is proved under the situation when motor speed up to the expected full load value when the maximum torque is developed while applying load under the normal operation.
In order to notice the graphical representation of the operational character of the induction motor, figure 14 illustrate the same.
Figure 15 on the other hand illustrate the effects of heavy loads at a factor of primary stator current and power.