The starting torque of the squirrel cage induction motor can be improved if the rotor resistance is increased. The double cage squirrel cage induction motor is used for the application which requires higher starting torque.
Why does squirrel cage motor have low starting torque?
Squirrel cage motors are the most commonly used induction motors, but the main drawback in them is their poor starting torque due to low rotor resistance. (Starting torque is directly proportional to the rotor resistance).
How can you increase the maximum torque of an squirrel cage IM?
The interaction of the magnetic fields produced by the stator and rotor windings produces a torque on the squirrel cage rotor. One big advantage of a squirrel cage motor is how easily you can change its speed-torque characteristics. This can be done by simply adjusting the shape of the bars in the rotor.
Which is are the methods to improve starting torque?
Starting torque of induction motor can be increased by increasing the rotor resistance. This can be done by reducing cross sectional area of rotor bars and by changing the conductor material. Following two types of rotor design’s are used. …
Which starter will give better starting torque to squirrel cage?
The Delta Start Starter is ideally suited for High Starting torque application, where squirrel cage induction motor is selected up to 50HP capacity. The Delta Star Starter also improves the power factor & reduces the demand on power supply system.
What type of motor has a low starting torque?
Large single-phase motors (15-50 hp) have been developed. These are capacitor start-capacitor run squirrel-cage induction motors. They are designed with very low inrush current and have low starting torque.
What is low starting torque?
So starting torque is low in induction motors. To get maximum starting torque, resistance is added to the rotor while starting slip ring motors, which is reduced gradually as motor picks up the speed. … So starting torque is low in induction motors.
What is full load torque?
The Full-load Torque is the torque required to produce the rated power of an electrical motor at full-load speed. In imperial units the Full-load Torque can be expressed as. T = 5252 Php / nr (1)
What is Torque slip characteristics?
Torque Slip Characteristics of Three Phase Induction Motor. The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine.
What is difference between squirrel cage and induction motor?
Key Differences Between Slip Ring & Squirrel Cage Induction Motor. The motor whose rotor is wound type such type of motor is called slip ring induction motor, whereas the squirrel cage motor, has a squirrel cage type rotor. … The starting torque of the slip-ring motor is high, whereas in squirrel cage motor it is low.
How can we reduce motor starting torque?
Motor torque almost is halved with significant reduction with respect to DOL method starting torque. … … By controlling the firing angle of the SCR the voltage that the device produces can be controlled during the starting of the motor by limiting the flow of power for only part of the duration of the sine wave.
What is starting torque in 3 phase induction?
Equation of Starting Torque of Three Phase Induction Motor
Starting torque is the torque produced by induction motor when it starts. We know that at the start the rotor speed, N is zero.
At which 5 to 7 times of full load current develops at starting?
This is because; during starting there is no back e.m.f, to oppose the initial rush-in of the current. So, Induction motors when connected “direct on-line”, draw 5 to 7 times the original full load current. At this time, they develop only 1.5 to 2.5 times the full-load torque.
Why the synchronous motor is not self starting?
Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. … Once the rotor nears the synchronous speed, the field winding is excited, and the motor pulls into synchronization.
Why is it called a squirrel cage motor?
Squirrel cage motors are a subclass of induction motors, which harness electromagnetism to generate motion. They are so-called “squirrel cage” motors because the shape of their rotor – the inner component connected to the output shaft – looks like a cage.
Which starter is suitable for 20 HP Delta connected squirrel cage induction motor?
So, this method is most suitable for a 20 kW squirrel cage induction motor. 3-point and 4-point starters are used for the starting of DC motors.