Lesson 1

ELECTRICAL MACHINES AND OVERCURRENT PROTECTION DEVICE 

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1. What are electrical machines?
Answer: Electrical machines are devices that convert electrical energy into mechanical energy or mechanical energy into electrical energy.
Examples: Motor, Generator, Transformer.

2. What are the types of electrical machines?
Answer: Generator: Converts mechanical energy into electrical energy.
Motor: Converts electrical energy into mechanical energy.
Transformer: Transfers electrical energy from one circuit to another through electromagnetic induction.

3. What is the working principle of a generator?
Answer: A generator works on the principle of electromagnetic induction. When a conductor moves in a magnetic field, it generates electricity.

4. What is the working principle of an electric motor?
Answer: An electric motor works on the principle of Lorentz force. When current flows through a conductor placed in a magnetic field, it experiences a force that causes the motor to rotate.

5. What is the role of a transformer?
Answer: It increases or decreases the voltage for power transmission.
Reduces power loss during long-distance transmission.
Ensures safe and efficient distribution of electricity.

6. What is overcurrent protection?
Answer: Overcurrent protection is a safety mechanism that automatically disconnects the power supply when excessive current flows through the circuit, preventing damage to electrical devices.

7. What are the causes of overcurrent?
Answer: Short circuit: When two live wires come in contact, causing high current flow.
Overload: When the current exceeds the safe capacity of the circuit.
Line fault: Damage or fault in the power line.
Loose connection: Improper wiring leading to current surge.

8. What are the types of overcurrent protection devices?
Answer: Fuse: Melts when excess current flows, breaking the circuit.
Circuit breaker: Automatically trips when overcurrent is detected.
Relay: Detects overcurrent and sends signals to control circuits.
MCB (Miniature Circuit Breaker): Automatically cuts off the power during overcurrent conditions.

9. What is the function of a fuse?
Answer: A fuse is a protective device that breaks the circuit by melting its wire when excessive current flows, preventing damage to appliances.

10. What is a circuit breaker?
Answer: A circuit breaker is an automatic electrical switch that protects electrical circuits from damage caused by overcurrent or short circuit by interrupting the flow of electricity.

11. What is the difference between a fuse and a circuit breaker?
Answer: Fuse: Melts and breaks the circuit when overcurrent occurs. It needs to be replaced after it blows.
Circuit breaker: Automatically trips during overcurrent and can be reset without replacement.

12. What is a relay?
Answer: A relay is an electrical device used to control a circuit by sending signals when overcurrent or voltage faults occur.

13. What is an MCB (Miniature Circuit Breaker)?
Answer: An MCB is a small circuit breaker that automatically disconnects the power supply in case of overcurrent or short circuit, protecting electrical appliances.

14. What is the importance of overcurrent protection?
Answer: Protects electrical machines from overheating and damage.
Prevents fire hazards caused by short circuits.
Ensures the stability of the electrical system.
Safeguards appliances and power lines.

15. What precautions should be taken for overcurrent protection?
Answer: Use appropriate fuses and MCBs for safety.
Regularly inspect electrical circuits.
Avoid overloading electrical systems.
Hire qualified electricians for installation and maintenance.
Properly maintain electrical machines.



EDIT BY : KRISHNA SAIKIA