Why starting torque of induction motor is low?
The induction motor draws a large starting current, but produces very low starting torque about 1.5 to 2.5 times the starting torque. The reason for low starting torque is the poor power factor of the rotor circuit. At the start, the rotor inductance is very high as compared to the rotor resistance.
The starting torque of an induction motor is low because the rotor of an induction motor is not directly connected to the stator's magnetic field. Instead, the rotor of an induction motor is indirectly coupled to the stator's magnetic field through the process of electromagnetic induction.
In an induction motor, the stator's windings produce a rotating magnetic field, and this rotating magnetic field is used to induce a current in the rotor of the motor. The current flowing through the rotor produces its own magnetic field, and the interaction between the stator's magnetic field and the rotor's magnetic field causes the rotor to rotate.
However, the rotor of an induction motor is not directly connected to the stator's magnetic field, and this indirect coupling reduces the amount of torque that the motor is able to produce at start-up. As a result, the starting torque of an induction motor is typically lower than the maximum torque that the motor is able to produce during its normal operation.
The starting torque of an Induction motor can be increased by using techniques such as adding a booster winding to the stator or using a capacitor in the circuit to boost the stator's magnetic field. However, these techniques can increase the starting torque of an induction motor only to a certain extent, and the starting torque of an induction motor will always be lower than its maximum operating torque.
In summary, the starting torque of an induction motor is low because the rotor of an induction motor is not directly connected to the stator's magnetic field. The indirect coupling between the rotor and the stator's magnetic field reduces the amount of torque that the motor is able to produce at start-up, and this is why the starting torque of an induction motor is typically lower than its maximum operating torque. The starting torque of an induction motor can be increased by using techniques such as adding a booster winding to the stator or using a capacitor in the circuit, but the starting torque of an induction motor will always be lower than its maximum operating torque.
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