Which of the following drive is used for metal-cutting machines tools, rolling mills etc

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Examoogle · Accepted Answer

Multimotor drive

Explanation: Multimotor drives are used in heavy industrial applications like rolling mills and complex machine tools where different parts of a machine require separate, coordinated motor control. This allows independent control over speed, torque, and positional accuracy for various sections of the process.

Working Principle: In a multimotor drive, separate motors are assigned to specific functional components of the machine, such as the main spindle, feed mechanism, and auxiliary cooling pumps. These motors are controlled via a centralized control system (like a PLC or VFD network) to ensure synchronization and precise mechanical coordination, which is impossible with a single motor or group drive.

Key Formulas: $P_{total} = \sum_{i=1}^{n} P_i$ — Total power delivered by individual motors; $\omega_1 = \omega_2$ — Synchronized angular velocity in coordinated sections

Key Points: Used when independent speed/torque control is required for different load points.; Essential in rolling mills for tension control between successive roll stands.; Reduces mechanical transmission complexity compared to group drives.; Provides high reliability as the entire machine doesn't stop if one motor fails.

Advantages: Independent control of different machine components.; High efficiency due to eliminated line-shaft losses.; Easy to automate with advanced electronic controllers.

Disadvantages: High initial investment and complex control circuitry.; Requires skilled maintenance for electronic drive systems.

Applications: Steel Rolling Mills; Paper Mills; Automated CNC Machine Tools; Conveyor Systems

Additional Info: Group drives are now mostly obsolete due to inherent energy losses in mechanical transmission.. Individual drive uses one motor per machine, whereas multimotor drive uses multiple motors for a single complex process.

Answer: C is correct — Multimotor drives are essential for complex machinery where various parts require independent speed, torque, or synchronous motion control.

Exam Tip: Always remember that in electrical machine exams, 'Multimotor' implies coordinated control, while 'Individual' is for simple single-operation machines.

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