In an induction motor, the concept of "breakdown torque" refers to the maximum torque that the motor can produce without stalling or losing synchronism. It is also known as "pull-up torque" or "starting torque." When an induction motor is initially started or experiences a sudden increase in load, it needs to produce a high torque to accelerate the load to its operating speed.
During motor start-up, the rotor (rotating part of the motor) accelerates from rest to its operating speed. The stator (stationary part of the motor) creates a rotating magnetic field that induces currents in the rotor, resulting in the generation of torque. The breakdown torque is the point at which the motor starts to approach its maximum torque capability, and any additional increase in load beyond this point may cause the motor to stall.
The ability of the motor to reach and maintain breakdown torque is essential for various applications, such as starting high-inertia loads, large pumps, compressors, and conveyors. The motor's design and construction, as well as the operating conditions, determine the value of the breakdown torque.
It's important to note that breakdown torque is different from the motor's rated or full-load torque, which is the maximum continuous torque the motor can deliver under normal operating conditions without exceeding its thermal limits. Once the motor has reached its operating speed and the load reaches its normal working conditions, the motor operates at or below its rated torque.