WORK EDUCATION

 

WORK EDUCATION

SAFETY DEVICES

1)    FUSE:

·        The safety devices which are used to protect the home appliances like          televisions, refrigerators, computers with damage by high voltage.

·        The fuse is made up of thin strip or strand of lead-tin alloy, whenever the heavy amount of current or an excessive current flow in an electrical circuit, the fuse melts and it opens the circuit and disconnects it from the power supply.

·        These strips are always connected in series with the circuit to protect from overcurrent in the running cables.

CIRCUIT DIAGRAM                                                           FUSE SYMBOL

          

 

 

TYPES OF FUSE:

1)    AC FUSE: AC fuses are smaller in size. They oscillated 50-60 times in every second from minimum to maximum. So there is no chance of Arc between the melted wires. Hence they can be packed in small size.

2)    DC FUSE: DC fuses are larger in size. DC supply has constant voltage above 0V so it is hard to neglect and turn off the circuit and there is a chance of an electric arc between melted wires. To overcome this, electrodes placed at larger distances and because of this the size of DC fuses get increased.

      APPLICATIONS: The fuses are the most important part of electrical and electronics      system and circuits. Here are some applications in which fuses are used, i.e.,

·        They are used in home distribution boards, general electrical appliances, and devices.

·        They are used in gaming consoles and all automobiles such as car, trucks and other vehicles.

·        They are also used in laptops, cell phones, printers, scanners, portable electronics, hard disk drives.

·        In the electrical distribution system, you will find fuses in capacitors, transformers, power converters, motor starters, power transformers.

·        They are used in LCD monitors, battery packs, etc.

 

 

2)  CIRCUIT BREAKER: An automatic device for stopping the flow of current in an   electric circuit as a safety measure.

SYMBOL

    TYPES:

1)    EARTH LEAKAGE CIRCUIT BREAKER: An Earth-leakage circuit breaker (ELCB) is a safety device used in electrical installations with high Earth impedance to prevent shock. It detects small stray voltages on the metal enclosures of electrical equipment, and interrupts the circuit if a dangerous voltage is detected.

The main purpose of Earth leakage circuit breaker (ECLB) is to stop damage to humans & animals due to electric shock

                                     

2)    MINIATURE CIRCUIT BREAKER: A Miniature Circuit Breaker (MCB) is an automatically operated electrical switch used to protect low voltage electrical circuits from damage caused by excess current from an overload or short circuit.

Nowadays we use an MCB in low voltage electrical network instead of a fuse. The fuse may not sense it but the miniature circuit breaker does it in a more reliable way. MCB is much more sensitive to overcurrent than fuse.

                                               

3) ISOLATOR: Isolator can be defined as; it is one type of mechanical switch used to isolate a fraction of the electrical circuit when it is required. Isolator switches are used for opening an electrical circuit in the no-load condition.