Practical Question on Electrical motorBy electricalsphere.com / October 14, 2025 3-Phase Motor Practical Q&A Guide Table of Contents Toggle 3-Phase Motor Practical Q&A GuideHow to wire a 3-phase motor?How to take continuity test of 3-phase motor?How to identify phase sequence of 3-phase motor?If a 3-phase motor is vibrating excessively, what are the possible causes?How would you detect a phase failure in a running motor?What are common reasons for motor overheating?How do you check for unbalanced load or voltage?If a motor runs slowly and draws high current, what would you inspect first?Calculate full load current of 5 HP motor.How to calculate cable size for a 7.5 kW motor?How is fuse or MCB rating decided?How to calculate motor output from torque and speed?What size contactor for 10 HP motor?What happens if two supply phases are interchanged?How to determine if a motor is Star or Delta connected?What information is found on motor nameplate?Why is earthing necessary for motor frame?What protection devices are used for 3-phase motor?What to check if motor hums but doesn’t start?How to safely reverse a 3-phase motor?Importance of thermal overload relay in starter circuit 3-Phase Motor Practical Q&A Guide -- Select a Question -- 1. How to wire a 3-phase motor? 2. How to take continuity test of 3-phase motor? 3. How to identify phase sequence of 3-phase motor? 4. If a 3-phase motor is vibrating excessively, what are the possible causes? 5. How would you detect a phase failure in a running motor? 6. What are common reasons for motor overheating? 7. How do you check for unbalanced load or voltage? 8. If a motor runs slowly and draws high current, what would you inspect first? 9. A 3-phase, 5 HP motor runs at 415 V with 0.85 PF and 88% efficiency. Calculate its full load current. 10. How do you calculate the size of cable required for a 7.5 kW, 3-phase motor? 11. How is motor protection fuse or MCB rating decided? 12. How do you calculate the motor’s power output in kW from torque and speed? 13. What size contactor should be selected for a 10 HP motor? 14. What happens if two supply phases are interchanged during connection? 15. How can you determine if a motor is connected in Star or Delta configuration? 16. What information can you read from a 3-phase motor nameplate? 17. Why is earthing necessary for every motor frame? 18. What protection devices are used for a 3-phase motor? 19. What should you check if a motor hums but doesn’t start? 20. How do you safely reverse the direction of a 3-phase motor? 21. What is the importance of thermal overload relay in a starter circuit?
