Skip to main content

Electric vs mechanical drive, individual vs group

Short answer

Electric drives are preferred because they offer wide speed control, simple starting, cleanliness, high efficiency, compact layout, electric braking, and automation. Individual drive is better than group drive because a motor fault stops only one machine, it gives independent speed control, higher efficiency, safer conditions, and easy expansion; these savings justify its higher initial cost.

Explain, why electric drive is preferred over mechanical drive? Also justify that individual drive is better than group drive.

Why electric drive is preferred over mechanical drive

A mechanical drive uses a steam engine, diesel engine or water wheel and a system of shafts, belts and gears; an electric drive uses an electric motor as the prime mover. Electric drives are preferred because:

  1. Easy and wide speed control: speed, torque and direction can be changed smoothly using starters, VFDs or converters.
  2. Simple starting and stopping: a push button or remote signal starts the motor at once; no warm-up time as in engines.
  3. Clean and quiet: no smoke, exhaust or fuel storage; low noise.
  4. High efficiency and low running cost: motors are 85–95 % efficient; losses in long line shafts and belts are avoided.
  5. Compact and flexible layout: the motor can be mounted directly on the machine, so machines can be placed anywhere in the shop.
  6. Wide range of ratings and characteristics: from fractional watts to many MW, with motors matching any load characteristic.
  7. Electric braking: plugging, dynamic and regenerative braking are available; regeneration returns energy to the supply.
  8. Automation and remote control: easy to interlock, automate and control with PLCs and sensors.
  9. Long life and low maintenance: squirrel-cage motors need little attention.
  10. Overload capacity and protection: short-time overloads are allowed, and overload/short-circuit relays protect the motor.

The only limits are dependence on a reliable supply and loss of drive during power failure.

Individual drive versus group drive

  • Group drive: one large motor drives a line shaft, and several machines take power from it by belts and pulleys.
  • Individual drive: each machine (or each operation of a machine) has its own motor.
PointIndividual driveGroup drive
Effect of motor faultOnly one machine stopsAll machines on the shaft stop
Speed controlEach machine controlled separatelyDifficult, all tied to shaft
EfficiencyHigh; motor near full loadLow; shaft/belt losses, motor often lightly loaded
Machine layoutFree; placed for best workflowFixed by line shaft position
Safety and cleanlinessNo overhead belts; safer, cleanerBelts and pulleys are hazards, dusty
Light in shopGood, no overhead shaftingObstructed by shafts and belts
ExpansionEasy: add machine with its own motorDifficult; shaft and motor redesign
Initial costHigher (many motors)Lower (one motor)

Justification: although group drive has lower first cost, individual drive gives better continuity of production, higher efficiency, independent speed control, safer working and easy expansion. Over the life of the plant, these savings outweigh the higher initial cost, so individual drive is the better choice for modern industries.

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Industrial Power Distribution and Illumination chapter 5 questions →