Why are squirrel cage induction motors not used for loads requiring high starting torque?

Main disadvantage of squirrel cage induction motor is that they have poor starting torque and high starting currents. Starting torque will be in the order of 1.5 to 2 times the full load torque and starting current is as high as 5 to 9 times the full load current.

Why do squirrel cage motors have low starting torque?

The rotor reactance depends on the slip. At start, the rotor reactance is large because slip of the motor at start is equal to unity. The large rotor reactance at start makes the starting torque of the motor poor. … That is why the starting torque of the squirrel cage induction motor is poor.

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What is the disadvantages of squirrel cage motor?

Some disadvantages of squirrel cage induction motors are: Very poor speed control. Although they are energy efficient while running at full load current, they consume a lot of energy on startup. They are more sensitive to fluctuations in the supply voltage.

How does torque increase in squirrel cage induction motor?

There were many attempts to design the rotor bar shape to increase the starting torque in squirrel cage induction motor, and it is well known that deep slot of rotor bar increases the starting torque. However, this deep slot increases the leakage flux so that it hurts the running efficiencies.

Which motor starting torque is better squirrel cage or wound type?

Wound-rotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit; as the motor accelerates, the resistance can be decreased. … Another important advantage over squirrel-cage motors is higher starting torque.

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.

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.

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What are the main advantage and disadvantage of a cage motor?

Squirrel Cage Induction Motors requires less conductor material than slip ring motor, hence copper losses in squirrel cage motors are less results in higher efficiency compared to slip ring induction motor.

What is the difference between slip ring and squirrel cage induction motor?

The slip ring motor has brushes for transferring the power whereas the squirrel cage motor is brushless. The copper loss in the phase wound motor is high as compared to squirrel cage motor. The efficiency of the slip ring motor is low whereas the squirrel cage motor has high efficiency.

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 type of motor has high starting torque?

DC motor has high starting torque.In a series motor the same current flows through the armature and the field winding.

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. …

What happens if fifth harmonics is given to induction motor?

What happens if fifth multiples of harmonics is given to induction motor? It will rotates in reverse direction.

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What are the advantages of a wound rotor motor over a squirrel cage motor?

The wound-rotor motors have the following advantages over the squirrel cage motors : (i) High starting torque and low starting current. (ii) Smooth acceleration under heavy load. (iii) No abnormal heating during starting.

Which type of starter is used only in slip ring induction motor?

Rotor resistance starter is used for slip ring induction motors of high ratings.

What is the formula for rotor turns per phase?

What is the formula for rotor turns per phase? Explanation: Firstly, the winding factor for stator is obtained along with the winding factor for stator. Next the ratio of the rotor voltage per phase to the stator voltage per phase.