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An induction motor having full load torque of 60Nm when DELTA connected develops a starting torque of 120Nm, For the supply voltage if motor is changed to STAR connection, the starting torque developed is ____? A) 40NmB) 60 Nm C) 90 Nm D) 120 Nm
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An induction motor having full load torque of 60Nm when DELTA connecte...
Explanation:

When an induction motor is delta-connected, it has a full load torque of 60 Nm. When it is connected in star, the starting torque developed changes.

Calculating the Starting Torque in Delta Connection:

The starting torque when the motor is delta-connected is given as 120 Nm. Therefore, the motor has a starting torque of 120 Nm when delta-connected.

Calculating the Starting Torque in Star Connection:

When the supply voltage is changed to star connection, the starting torque developed can be calculated using the following formula:

Ts = (3/2) * V^2 / Rr

Where Ts is the starting torque, V is the line voltage, and Rr is the rotor resistance.

Since the full load torque of the motor is 60 Nm, we can assume that the rotor resistance is 0.1 ohms.

Therefore, the starting torque developed when the motor is star-connected is:

Ts = (3/2) * V^2 / Rr
Ts = (3/2) * (V/√3)^2 / 0.1
Ts = (3/2) * V^2 / 0.3

To find the value of V that gives a starting torque of 60 Nm, we can substitute Ts = 60 Nm and solve for V:

60 = (3/2) * V^2 / 0.3
V^2 = 60 * 0.3 * 2 / 3
V^2 = 36
V = √36
V = 6√2 volts

Therefore, the starting torque developed when the motor is star-connected is:

Ts = (3/2) * V^2 / 0.3
Ts = (3/2) * (6√2/√3)^2 / 0.3
Ts = (3/2) * 72 / 0.3
Ts = 90 Nm

Therefore, the correct answer is option C) 90 Nm.
Community Answer
An induction motor having full load torque of 60Nm when DELTA connecte...
40nm
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An induction motor having full load torque of 60Nm when DELTA connected develops a starting torque of 120Nm, For the supply voltage if motor is changed to STAR connection, the starting torque developed is ____? A) 40NmB) 60 Nm C) 90 Nm D) 120 Nm Related: Synchronous Motor (Part - 2) - Synchronous Machines, Electrical Machines
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An induction motor having full load torque of 60Nm when DELTA connected develops a starting torque of 120Nm, For the supply voltage if motor is changed to STAR connection, the starting torque developed is ____? A) 40NmB) 60 Nm C) 90 Nm D) 120 Nm Related: Synchronous Motor (Part - 2) - Synchronous Machines, Electrical Machines for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about An induction motor having full load torque of 60Nm when DELTA connected develops a starting torque of 120Nm, For the supply voltage if motor is changed to STAR connection, the starting torque developed is ____? A) 40NmB) 60 Nm C) 90 Nm D) 120 Nm Related: Synchronous Motor (Part - 2) - Synchronous Machines, Electrical Machines covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An induction motor having full load torque of 60Nm when DELTA connected develops a starting torque of 120Nm, For the supply voltage if motor is changed to STAR connection, the starting torque developed is ____? A) 40NmB) 60 Nm C) 90 Nm D) 120 Nm Related: Synchronous Motor (Part - 2) - Synchronous Machines, Electrical Machines.
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