--- title: "Electric vs mechanical drive, individual vs group" subject: "Industrial Power Distribution and Illumination" chapter: 5 key: "semester_6/industrial_power_distribution_and_illumination:electric-vs-mechanical-drive" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/electric-vs-mechanical-drive site: BCT Engineering --- # Electric vs mechanical drive, individual vs group Industrial Power Distribution and Illumination · Chapter 5: Electrification of Industrial Building - Asked in: 2068 Jestha (old course), 8 marks - Video: [Electrical Drive and Its Types | Difference Between Electrical and Mechanical Drive | #SBTE #Exam](https://www.youtube.com/watch?v=sIUZALG7Gi4) — CRAZY POLYTECHNIC - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/electric-vs-mechanical-drive - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-5 ## Question Explain, why electric drive is preferred over mechanical drive? Also justify that individual drive is better than group drive. ## 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. ## Answer #### 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. | Point | Individual drive | Group drive | |---|---|---| | Effect of motor fault | Only one machine stops | All machines on the shaft stop | | Speed control | Each machine controlled separately | Difficult, all tied to shaft | | Efficiency | High; motor near full load | Low; shaft/belt losses, motor often lightly loaded | | Machine layout | Free; placed for best workflow | Fixed by line shaft position | | Safety and cleanliness | No overhead belts; safer, cleaner | Belts and pulleys are hazards, dusty | | Light in shop | Good, no overhead shafting | Obstructed by shafts and belts | | Expansion | Easy: add machine with its own motor | Difficult; shaft and motor redesign | | Initial cost | Higher (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. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which is a reason electric drive is preferred over mechanical drive? A. Needs warm-up time like engines B. Easy, wide speed control and electric braking, with clean, quiet and automated operation C. Depends on line shafts and belts D. Cannot be remotely controlled Answer: B. Electric drives give smooth speed/direction control, instant start, electric braking, cleanliness and automation. (Key point: Why electric) 2. What is a group drive? A. Each machine has its own motor B. One large motor drives a line shaft that feeds several machines through belts and pulleys C. Several motors drive one machine D. A drive using batteries Answer: B. In group drive one motor and a line shaft power several machines; in individual drive each machine has its own motor. (Key point: Group drive) 3. What happens when the motor fails in each arrangement? A. Individual: all machines stop; group: only one stops B. Individual: only that machine stops; group: all machines on the shaft stop C. Both stop everything D. Neither stops Answer: B. Individual drive isolates faults to one machine, improving continuity of production. (Key point: Fault effect) 4. How is the higher first cost of individual drive justified? A. It is not justified B. Better continuity, higher efficiency, independent speed control, safety and easy expansion outweigh it over plant life C. Because it uses only one motor D. Because belts last longer Answer: B. Although group drive is cheaper initially, individual drive saves more over the life of the plant. (Key point: Cost trade-off) ## Related in Industrial Power Distribution and Illumination - [Electric drive and motor selection factors](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aelectric-drive-motor-selection) — Industrial Power Distribution and Illumination, chapter 5 - [Types of electric wiring system compared](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Awiring-systems-comparison) — Industrial Power Distribution and Illumination, chapter 5 ## Related in other subjects - [Group vs individual drive; constant torque vs power](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Agroup-individual-constant-torque-power-drive) — Utilization of Electrical Energy, chapter 2 - [Group drive vs individual drive](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Agroup-vs-individual-drive) — Utilization of Electrical Energy, chapter 2 - [Individual, group and multi-motor drives](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Aindividual-group-multimotor-drive) — Utilization of Electrical Energy, chapter 2 - [Group drive vs multimotor drive](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Agroup-vs-multimotor-drive) — Utilization of Electrical Energy, chapter 2