1) The document discusses the torque-slip characteristics of induction motors. It aims to derive the expression for gross torque as a function of slip, sketch the torque-slip characteristics, and derive the expression for maximum torque and the slip it occurs at. 2) It introduces the torque-slip characteristics and objectives of deriving relevant expressions. The induced torque equation and torque-slip characteristics are discussed. 3) For large slips beyond maximum torque, the torque-slip characteristic follows a rectangular hyperbola. References on electrical machines are provided.

1. AC MACHINES (2140906)
Active Learning Assignment
on
TORQUE – SLIP CHARACTERISTICS
Gandhinagar Institute of Technology
Electrical Department
Batch-B3

2. Synopsis
• Instructional Objectives
• Introduction
• Induced Torque Equation
• Torque – slip characteristics
• References

3. Instructional Objectives
• Derivation of the expression for the gross torque developed as a function of slip
(speed) of Induction motor
• Sketch the above characteristics of torque-slip (speed), explaining the various
features
• Derive the expression of maximum torque and the slip (speed) at which it occurs
• Draw the above characteristics with the variation in input (stator) voltage and
rotor resistance

4. Introduction
• The relation between the rotor input, rotor copper loss and rotor output (gross) are
derived next. Finally, the various losses − copper losses (stator/rotor), iron loss
(stator) and mechanical loss, including the determination of efficiency, and also
power flow diagram, are presented. In this lesson, firstly, the torque-slip (speed)
characteristics of IM, i.e., the expression of the gross torque developed as a
function of slip, will be derived. This is followed by the sketch of the different
characteristics, with the variations in input (stator) voltage and rotor resistance,
along with the features. Lastly, the expression of maximum torque developed and
the slip (speed) at which it occurs, are derived.

5. Induced Torque Equation

6. Torque – slip characteristics

8. • Hence for large value of slip (beyond maximum or pull-out torque) the torque -
slip characteristic is rectangular hyperbola.

10. REFERENCES
• CHARLES I HUBER “ELECTRICAL MACHINES”
• A TEXBOOK OF ELECTRICAL MACHINES BY B.L.THERAJA
& A.K THERAJA
• A TEXBOOK OF AC MACHINE BY “J.G.JAMNANI”