MCB and Fuse (11).pptx

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1. MCB and Fuse Understanding the meaning of MCB

2. Meaning of MCB . MCB stands for  Miniature Circuit Breaker . It is an electromechanical device that works based on the electromagnetic as well as the thermal properties of the electric current. An electromagnetic mechanism present inside the MCB helps it to instantaneously interrupt the current flow during short circuits and the bimetallic strip present in it helps it to interrupt the current flow during overloads.

3. Working Principle of MCB Working Principle of MCB When the current overflow occurs through MCB – Miniature Circuit Breaker, the bimetallic strip gets heated and deflects by bending . The deflection of the bi-metallic strip releases a latch. The latch causes the MCB to turn off by stopping the current flow in the circuit.

4. Types of MCB Different Types of MCB  Based on their Trip Curves These are some features of the MCB: Its current rating is a hundred amperes. It operates thermally. Usually, its tripping is not controllable. MCB can be easily operated and thus offers improved operational safety and greater convenience without incurring an expensive operating cost.  They find use to protect lower current circuits and have the following specifications:  Current rating – Amperes Short Circuit Rating – Kilo Amperes (kA)  Operating Characteristics – B, C, D, Z or K Curves

5. Continued….. Type B MCB Type C MCB Type D MCB Type K MCB Type Z MCB Type B MCB B types trip if the current flowing through hits between three and five times the recommended maximum. Type B is the most sensitive types of MCB, designed for domestic and low voltage commercial settings where any current surges are likely to be small like lighting circuits, home wirings, etc. Functions of Type B MCB  are protection for people and big-length cables in TN and IT systems.

6. Type C MCB Type C MCB C types trip at currents between five and ten times their rated load. They find use in commercial or industrial types of applications where there could be chances of higher values of short circuit currents in the circuit. Good examples include smaller electric motors, fans, fluorescent lighting, small transformers, pilot devices, control circuits, coils, etc. Functions of Type C MCB  are protection for resistive and inductive loads with low inrush current

7. Type D Type D MCB D type MCBs are the least sensitive type, only activating when current surges to between ten and twenty times the recommended maximum.  Examples include welding equipment, X-ray machines, UPS systems, large motors, uninterruptible power supply units, industrial welding equipment, etc. Functions of Type D MCB  are protection for circuits that supply loads with high inrush current at the circuit closing (transformers, breakdown lamps). 

8. Tripping Current and Operating Current of MCB’s Type Tripping Current Operating Time Type B   3 To 5 times the full load current 0.04 To 13 Sec Type C   5 To 10 times the full load current 0.04 To 5 Sec Type D   10 To 20 times the full load current 0.04 To 3 Sec Type K   8 To 12 times the full load current <0.1 Sec Type Z   2 To 3 times the full load current <0.1 Sec

9. Types of MCBs based on the number of poles Single Pole MCB Double pole MCB Triple Pole MCB Three poles with a neutral  Four Poles

10. Explanation Single Pole MCB A single-pole circuit breaker has one switch and also protects a single phase of the circuit. Double pole MCB The double pole circuit breaker has two switches and also protects two-phase and neutral. Triple Pole MCB A three-pole circuit breaker has three switches, and they also protect the three phases. Three poles with a neutral Three poles and a neutral circuit breaker protect the three phases of the circuit. It also has a neutral switch. Four Poles A four-pole MCB contains four switches, three phases, and a neutral. But unlike the three poles with neutral, the four poles protect all the phases and the neutral. They are used in places with an unbalanced circuit.

11. Types of MCB amps Ratings The following lists some of the most frequently encountered load capacities for commercial MCBs: 6 amps 10 amps 16 amps 20 amps 25 amps 32 amps Applications of MCB’s Home Electrical Panels Heaters Lights Industrial Applications(  industries requires up to 30 kA of power supply)

12. Are There Any Disadvantages to MCB? MCBs are more expensive than fuses.  MCB distribution board is more costly than a rewireable fuse board The probability of overloading the circuit is eliminated by operating by someone who is unqualified. Advantages Of MCB’s MCBs allow quick restoration of power supply. MCBs are safer than a fuse.  MCBs offer better protection against electrical faults MCBs are much more sensitive to faults than fuses They act faster than fuse during short circuits Offer better overload protection than fuses. Offers a safer interruption of short-circuit current and arc quenching. Handling MCB is electrically much safer than a fuse.

13. Practical Based On MCB

14. Overload Circuit

15. Fuses

16. Transistor Checking

17. Images For Fuses

18. Working Principle of an Electrical Fuse Current flows in a loop Heating effect of current Electric current can flow through a conductor only when the circuit formed is complete. If there is a break in the loop, electric charges cannot flow through. This is also how switches operate. For example, when you put on the light switches at home, the lights come on because you have just completed the circuit allowing charges from the power source to flow through and power your lights.

19. Types of Fuses Different types of fuses are available in the market, and they are classified on the basis of different aspects. But mainly, fuses can be divided into two categories based on the input supply as follows: AC fuses DC fuses

20. Principle of Electrical Fuse The primary use of an electric fuse is to protect electrical equipment from excessive current and to prevent short circuits or mismatched loads. Electrical fuses play the role of miniature circuit breakers. Apart from protecting equipment, they are also used as safety measures to prevent any safety hazards to humans.

21. Electrical Fuse - The Working Principle Introduction An electrical fuse is a safety device that operates to provide protection against the overflow of current in an electrical circuit. An important component of an electrical fuse is a metal wire or strip that melts when excess current flows through it. It helps to protect the device by stopping or interrupting the current. In this article, let us know in detail about the Working Principle of the electrical fuse and its functions and types.

22. Function of Fuse Acts as a barrier between the electric circuit and the human body Prevents device failure due to faulty circuit operation Fuse prevents short-circuits Prevents overload and blackouts Prevents damage that is caused due to mismatched loads

23. Experiment Describe an experiment to illustrate the action of an electric fuse. Take a thin fuse wire made of tin or tin-alloy having low melting point. Place this fuse wire on the porcelain fuse grip and insert the grip into the fuse holder. Now switch on all the electrical appliances of high power rating like electric iron, water heater, air conditioner, etc., . Since the melting point of the fuse wire is much lower, it melts and breaks the circuit.

24. Give the circuit symbol for a fuse. Explain its importance in a circuit. A fuse is a very important device used for protecting electric circuits. It is a wire made out of a metal like tin or tin alloy having a very low melting point. When a high current flows through a circuit, the fuse wire gets heated or melts due to short circuiting or overloading. Hence the circuit is broken and the current stops flowing. This saves all the appliances of the circuit. Fuse wires are of various capacities. A fuse with 5 ampere capacity will be thinner than a fuse with 15 ampere capacity. A fuse of 5 amps is used in circuits where lights and fans are connected whereas a fuse of 15 amps is used in power circuits where appliances like electric heater, geyser, electric iron and air conditioner are connected.

25. Selection of swithces SPST = Single Pole, Single Throw SPDT = Single Pole, Double Throw DPST = Double Pole, Single Throw DPDT = Double Pole, Double Throw

26. Continued..... Pole - number of switch contact sets. Throw - number of conducting positions (only used for single and double) Way - number of conducting positions. Momentary - switch returns to its normal position when released. Open - off position, contacts not conducting. Closed - on position, contacts conducting, there may be several on positions.

27. SPST-Switch ON-OFF, SPST SPST = Single Pole, Single Throw SPST on-off switch symbolSPST toggle switch, photograph © Rapid Electronics A simple on-off switch. This type can be used to switch the power supply to a circuit. The photograph shows a SPST toggle switch When used with mains electricity this type of switch must be in the live wire, but it is better to use a DPST switch to isolate both live and neutral. Rapid Electronics: SPST toggle switch

28. Earthing Earthing is used to protect you from an electric shock. It does this by providing a path (a protective conductor) for a fault current to flow to earth. It also causes the protective device (either a circuit-breaker or fuse) to switch off the electric current to the circuit that has the fault. An earthing system or grounding system connects specific parts of an electric power system with the ground, typically the Earth's conductive surface, for safety and functional purposes

29. Earthing Rules According to IEE regulations and IE rules, earth pin in 3 pin plus sockets and 4 pin power sockets must be efficiently and permanently earthed. All metal casings and metal coverings containing or covering electrical supply cable or equipment must be earthed. The metallic frames of generators, transformers, stationary motors etc. Stay wires for the overhead electric lines must be connected to earth at atleast one strand to the earth wires.

30. Without Earting....Causes

31. Fault current......

32. Earthing Construction...

33. Types of earthing Types of Earthing There are three types of earthing, they are: Pipe earthing Plate earthing Strip earthing

34. Plate Earthing and Strip Earthing

35. Rod earthing Images...

36. Earthing Rules According to IEE regulations and IE rules, earth pin in 3 pin plus sockets and 4 pin power sockets must be efficiently and permanently earthed. All metal casings and metal coverings containing or covering electrical supply cable or equipment must be earthed. The metallic frames of generators, transformers, stationary motors etc. Stay wires for the overhead electric lines must be connected to earth at atleast one strand to the earth wires.

37. Components of Electrical Earthing System Earth Continuity Conductor Earthing Lead Earth Electrode Earth Continuity Conductor or Earth Wire The conductor that connects all metallic part of the electrical installation like the conduit, metallic shells, ducts, plug sockets, distribution boxes, fuses, controlling and regulating devices, metallic parts of transformers, motors, generators etc.

38. Earth Continuity Conductor(Cable) The conductor that connects all metallic part of the electrical installation like the conduit, metallic shells, ducts, plug sockets, distribution boxes, fuses, controlling and regulating devices, metallic parts of transformers, motors, generators etc.

39. Earth Continuity Conductor (bare copper conductor Earth Continuity Conductor (bare copper conductor. The earth continuity conductor’s resistance must be very low. As per IEEE rules, the resistance between the consumer earth terminal and the earth continuity conductor must be less and 1 ohms.

40. Earthing Lead or Earthing Joint he conductor connecting the earth continuity conductor and the earth electrode is called earthing lead or earthing joint. The point where the earthing lead meets the earth continuity conductor meet is called connecting point. Copper strip used as Earthign Lead If there are 2 earth electrode there should be 4 earthing leads. This isn’t for providing parallel path for fault current but for carrying fault current simultaneously giving added safety.

41. Copper strip used as Earthign Lead

42. Important Terms Earth: The connection of an electrical installation through a conductor to another conductor buried in earth. Solidly Earthed: An electrical installation or appliance is said to be solidly earthed when it is connected to earth conductor/wire directly without using a circuit breaker, fuse, impedance or any other safety devices or elements Earth Electrode: A conductor buried in earth for the purpose of electrical earthing is known as earth electrode. The shape of the earth electrode may vary from conductive rod, conductive plate, metal water pipe or any other conductor with low resistance. Earth electrodes are made of copper, galvanised iron, cast iron etc.

43. Continued.... Earth Lead: The conductive strip or wire that connects an electrical installation or appliance to the earth electrode is called Earth Lead. Earth lead can be of copper, galvanized iron etc. Sub Main Earthing Conductor: the wire connecting the distribution board to various switch boards. Flexible wires are used as sub main earthing conductor. Earth Continuity Conductors: They are the conductors used for connecting the earth lead to various electrical appliances and devices such as distribution boards, electrical sockets, appliances etc. It may be in the form of flexible wire, cable metallic covering or metallic pipe. Earth Resistance: The resistance between the earth and earth electrode is called earth resistance. It is the resistance of earth electrode, earth lead, earth continuity conductor and earth added up algebraically. The earth resistance is measured using Earth Megger.

44. Advantages of Earthing Earthing is the safe and the best method of offering safety. We know that the earth’s potential is zero and is treated as Neutral. Since low equipment is connected to earth using low resistance wire, balancing is achieved. Metal can be used in electrical installations without looking for its conductivity, proper earthing ensures that metal does not transfer current. A sudden surge in voltage or overload does not harm the device and person if proper earthing measures are done. It prevents the risk of fire hazards that could otherwise be caused by the current leakage.

45. Definition of Earthing... Earthing is defined as “the process in which the instantaneous discharge of the electrical energy takes place by transferring charges directly to the earth through low resistance wire.” To ensure safety, earthing can be done by connecting the electrical appliance to earthing systems or electrodes placed near the soil or below the ground level. The electrode or earthing mat equipped with a flat iron riser is installed under the ground level. It helps to connect all the non-current-carrying metallic parts of the equipment

46. Resistors sries and Parallel Connection you can calculate the voltage across the three resistors at a time and the formula is .

47. Series Connection Two or more resistors are said to be connected in series when the same amount of current flows through all the resistors. In such circuits, the voltage across each resistor is different. In a series connection, if any resistor is broken or a fault occurs, then the entire circuit is turned off. The construction of a series circuit is simpler compared to a parallel circuit.

48. Continued.... The figure above shows the ‘n’ number of resistors connected in parallel. The following relation gives the total resistance here Circuit Components

49. Ohm's law Ohm's law states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperatures remain constant.

50. Problems Based On Ohm’s Law

51. Roles and Responsibilities of an electrician Installs and repairs electrical wiring, systems, and fixtures in buildings. Installs conduits and pipes to house electrical wires and cables. Ensures piping complies with electrical codes. Installs circuit breakers and other electrical hardware and connects wiring to them. Connects electrical systems to powerlines to provide electricity to the building. Tests electrical systems to ensure proper installation and operation. Inspects electrical systems to determine whether repairs are needed. Replaces conduit and wiring as needed. Required Skills/Abilities: Ability to read blueprints. Extensive knowledge of electrical systems and wiring. Ability to use hand tools and power tools. Proficient in the use of test meters and other diagnostic equipment. Excellent analytical and problem-solving skills.

52. What is Electrical Safety? Electrical safety is a general practice of workers who are exposed to handling and maintaining electrically powered equipment. It is a set of guidelines they follow to mitigate electrical hazards and prevent its dangerous effects in case of an incident. Unable to adhere to electrical safety can lead to accidents, near misses, or even fatalities . Importance Working around electricity can be very safe on the job site when workers properly identify and control hazards. But, inadequate training, lack of experience, and failure to recognize potential hazards could result in electric shock or death.

53. Electrical Hazards Examples & Tips for Safety Overhead Power Lines Overhead powered and energized electrical lines have high voltages which can cause major burns and electrocution to workers. Remember to maintain a minimum distance of 10 feet from overhead power lines and nearby equipment.

54. Continued... Damaged Tools and Equipment Exposure to damaged electrical tools and equipment can be very dangerous. Do not fix anything unless you are qualified to do so. Inadequate Wiring and Overloaded Circuits Using wires of inappropriate size for the current can cause overheating and fires to occur. Use the correct wire suitable for the operation and the electrical load to work on. Use the correct extension cord designed for heavy-duty use.

55. Continued.... Exposed Electrical Parts Examples of exposed electrical parts include temporary lighting, open power distribution units, and detached insulation parts on electrical cords. Improper Grounding The most common OSHA electrical violation is the improper grounding of equipment. Proper grounding can eliminate unwanted voltage and reduce the risk of electrocution.

56. Continued.... Damaged Insulation Defective or inadequate insulation is a hazard. Be aware of damaged insulation and report it immediately. Wet Conditions Never operate electrical equipment in wet locations. Water greatly increases the risk of electrocution especially if the equipment has damaged insulation.

57. Safety signs....

58. Continued....