The drive which is used for metal-cutting machines tools, rolling mills etc. are

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Multimotor drive

Explanation: A multimotor drive is used in heavy industrial applications where different parts of a machine tool or rolling mill require separate motors for independent control of speed, torque, and synchronization. This approach allows for higher precision and efficiency compared to group drives or single-motor systems in complex mechanical processes.

Working Principle: In a multimotor drive system, multiple electric motors are deployed to operate different sections of a manufacturing machine (e.g., feed motor, spindle motor, and coolant pump in a CNC machine). Each motor is controlled by a dedicated power electronic drive or controller (like a VFD or Servo Drive), which allows for coordinated motion control and independent acceleration or deceleration profiles as required by the process load.

Key Formulas: $P_{total} = \sum_{i=1}^{n} P_i$ — total power requirement is the summation of individual motor ratings.; $T_{load} = J \frac{d\omega}{dt} + B\omega + T_L$ — dynamics of an individual motor-load shaft.

Key Points: Independent control of different segments of the machine.; Higher efficiency due to absence of mechanical power transmission losses (belts, pulleys).; Essential for complex sequence operations like in paper mills or rolling mills.; Provides flexibility for varying load requirements on different machine parts.

Advantages: Flexible speed and torque control for individual parts.; High reliability; failure of one motor does not necessarily halt the entire process.; Eliminates line shafting and mechanical transmission losses.

Disadvantages: Higher initial cost due to multiple motors and controllers.; Increased complexity in control circuitry and wiring.; Requires complex synchronization systems for multi-motor tracking.

Applications: Rolling Mills; Paper Mills; CNC Machine Tools; Printing Presses

Additional Info: Individual drive: Single motor for a single machine tool.. Group drive: One motor drives multiple machines via a line shaft and belts (rarely used now due to high losses).. Multimotor drive: Multiple motors for a single complex machine.

Answer: C is correct — Multimotor drives are essential for metal-cutting tools and rolling mills to provide independent, precise control for various mechanical components of the system.

Exam Tip: Always relate the drive type to the mechanical load requirement; rolling mills require high torque at varying speeds, making individual motor control (Multimotor) necessary for dynamic performance.

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