The torque-speed characteristics of a 60-Hz induction motor and a load are shown in Figure Pl 7.

step 1 As we know that n s is equal to 120 f by p So p is equal to 120 multiplication 60 by 18000 which

The torque-speed characteristics of a 60-Hz induction motor...

The torque-speed characteristics of a $60-\mathrm{Hz}$ induction motor and a load are shown in Figure $\mathrm{Pl} 7.30 .$ How many poles does the motor have? In steady-state operation, find the speed, the slip, the output power, and the rotor copper loss. Neglect rotational losses.

Key Concepts

Output Power

Output power in an induction motor refers to the mechanical power delivered to the load. It is calculated as the product of the developed torque and the angular speed of the rotor. Understanding this concept allows one to assess the motor’s ability to perform work and to evaluate its efficiency in converting electrical energy into mechanical energy.

Torque-Speed Characteristic

The torque-speed characteristic graph of an induction motor displays how the torque output varies with rotor speed. This curve is crucial for determining the operating point of the motor when connected to a given load, as it helps in balancing the motor’s developed torque with the load torque while also indicating the stability of the operation at that point.

Rotor Copper Losses

Rotor copper losses are the power losses occurring in the rotor windings due to the resistance of the copper conductors and the slip between the rotor and the rotating magnetic field. These losses represent the portion of the electrical input power that is not converted into mechanical output power, providing insight into the efficiency and thermal performance of the motor.

Synchronous Speed

Synchronous speed is the theoretical speed at which the magnetic field in an induction motor rotates. It is determined by the supply frequency and the number of poles of the motor using the formula n? = (120 × frequency) / number of poles. This concept is essential in determining the motor’s operating point and directly relates to the selection of the number of poles for a given supply frequency.

Slip

Slip is the difference between the synchronous speed of the motor's magnetic field and the actual rotor speed, expressed as a fraction of the synchronous speed. It quantifies how much slower the rotor is operating compared to the magnetic field, and is a key parameter used to analyze motor performance, affecting both torque production and efficiency.

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