So far, we have understood that the value of the torque is calculated by the following expression:
With the mentioned value, we can say:
- Torque is directly proportional to slip s, which means torque is zero when slip is zero
2.a When the value of slip ‘s’ is very low, it will state that torque T is proportional to the slip. The condition of the proportion will be realized when rotor resistance R2 is constant. When slip‘s’ is very low, it will lead to smaller value of the term sX2 which becomes negligible as compared to R2. The torque-speed and torque-slip will curve when speed is almost near to the synchronized speed.
2.b When the speed decreases in the presence of increasing load, the slip ‘s’ will also increase which leads to rise in Torque. The value of the Torque will reach the maximum value when slip‘s’ will be equal to fraction of R2 and X2, i.e.
When the Torque reaches the maximum value, it is termed as, “pull-out” and “break-down” torque.
2.c When you further increase the slip, it will result into decreasing value of Torque. When the slip’s’ is increased, the motor work under maximum value of torque corresponding to the value of slip. Considering the equation,
This happens when the standstill reactance will become constant
Although we mentioned that torque is independent of the value of rotor resistance, R2 as seen the figures, we can state that the location of Tm is dependent of the value of R2. Therefore, we can say that when R2 increases the value of the slip where the maximum torque is observed also occurs at the same page.
As seen in the 2nd equation and both the figures, the rectangular hyperbola of speed-torque or slip-torque is observed when the speed or slip goes beyond the maximum torque value. In addition to the same, it is also observed in the figures that torque –speed and slip curves with various values of Rotor resistance R2.
- Current Electricity Basic Concepts
- Introduction to Alternating Current
- Introduction Three Phase A C Circuits
- Magnetic Field
- General Aspects
- General Aspects Polyphase Induction Motors
- Classification of A C Motors
- Constructional Details
- Production of Rotating Magnetic Field
- Theory of Operation of an Induction Motor
- Frequency of Rotor Current
- Rotor E M F and Rotor Current
Links of Next Electrical Engineering Topics:-
- Operating Characteristics 3 Phase Squirrel Cage Induction Motor
- Shows a Wound Rotor Induction Motor with Controller Rheostat
- Power Stages in an Induction Motor
- Induction Motor as Transformer
- Equivalent Circuit of an Induction Motor
- Starting of Induction Motors
- Factors Governing Performance of Induction Motors
- Effects of Operating Conditions
- Ratings of 3 Phase Induction Motors
- Squirrel Cage Motors Advantages Disadvantages and Applications
- Wound Rotor or Slip Ring Induction Motors Advantages Disadvantages and Applications
- Comparison of a Squirrel Cage and a Slip Ring or Phase Wound
- Comparison Induction Synchronous Motors
- Highlights in Polyphase Induction Motors
- Single Phase Motors
- Characteristics of D C Generators
- Measuring Instruments
- Power Supply System