In this article , we shall discuss about various torque ratios of induction motor. While study about torque in an induction motor various types of torque involved in it. They are classified as starting torque, Running Torque, Full load toque and maximum torque. Each of these related with one another. So it is important to study about these ratios will be much better to understand about working condition of motor.
The various kind of torque ratios of induction motor involved as listed below
- Full load (TFL)to maximum Torque ratio (TM)
- Starting torque (TST) to maximum torque ratio (TM)
Before study above ratios , it is so important to be known about terms of individual torque
Starting Torque of Motor
When motor is in stand still i.e , at instant of electrical power supplied to motor, The speed of motor will be zero (0) rpm. It means slip (s) is 100% (or) 1.
By putting S =1 in general torque equation we get equation of starting torque of motor
Starting torque defined as torque produced by motor when the motor is being started
Maximum Torque of motor
When slip is in maximum (sm) in motoring region , it develops maximum torque in motor. It also can be said as condition for maximum torque produced in motor is (sm)= R2/X2).
The maximum torque of motor is defined as , it is ability to generate maximum torque at normal motoring condition , while slip of motor is s = sm.
Full Load Torque of motor
While a motor is working in normal working condition, it is slip is related to amount of load connected with it. if slip (s) is corresponding to load then,
The magnitude of torque generated by a motor when , it is connected with its maximum capacity load can be driven.
Starting torque to Maximum torque ratio
To get starting torque to maximum torque ratio we divide (or) substitute starting torque to maximum torque
By simplifying above equation and dividing both numerator and denominator by X22 we get
We know than maximum slip Sm = R2/X2 and substitute is above equation
In Some times ratio of sm can be said as “a”
The above mathematical expression indicates ratio of starting toque to maximum torque of motor.
Ratio of Full load torque to Maximum torque
By substituting maximum torque to full load torque of motor
Simplifying above equation and dividing both numerator and denominator by X22 , we get
Here, When slip is in maximum (sm) in motoring region , it develops maximum torque in motor. It also can be said as condition for maximum torque produced in motor is (sm)= R2/X2).
In Some times ratio of sm can be said as “a”
