Circuit Breaker
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The document discusses different types of circuit protection devices including fuses, miniature circuit breakers (MCBs), molded case circuit breakers (MCCBs), and earth leakage circuit breakers (ELCBs). It provides details on how each device works, when they are used, and their advantages. MCBs are described as the most modern substitute for fuses, providing overload and short circuit protection. ELCBs are important safety devices that can prevent electric shock for installations with high earth impedance. The document includes diagrams of components inside an MCB and how an ELCB works.
Circuit Breaker
- 1. By: Sheel T. Shah mastersheel007@gmail.co
- 3. • It is the Simplest • ‘Miniature • ‘Moulded Case • ‘Earth Leakage Form of Circuit Breaker’ Circuit Breaker’ Circuit-Breaker’ Protection (MCB). (MCCB). (ELCB). Against Excess • It is a • It Provides Over • It is Current Current, Short Electromagnetic Load and Short Operated Circuit and Earth Device which Circuit Device Designed Fault. Operates and Protection to to operate when • A Fuse is a Wire Disconnects the Normal Service a leakage of Short Length Circuit Reaches apart from Current Exceeds having Low - a Pre- Serving as a Pre- Melting Point. Determined ‘Circuit - Determined Value. Breaker’. Value.
- 4. INTRODUCTION • An MCB is an Electromagnetic Device which Operates and Disconnects the Circuit when the Current reaches a pre determined value. The MCB may , therefore, be used in lieu of fuse & can be fitted in consumer’s distribution panel. • It is most modern substitute for conventional rewireable fuse with most accurate & efficient system in over-load & short circuit protection. In fact, it provides over-load protection & short circuits protection whereas FUSE offers short circuit protection only. • An MCB will normally operate at 1.25 times it rated current i.e. 20 A. MCB operates at 25 A compared with 30 A for cartridge fuse or 40 A for rewireable type of fuse of the same rating. Some manufactures have invented most efficient MCB which operates at 1.05 times the full load current. • Other advantages of MCB are that they can be quickly reset by hand after operations without any cost and they cannot be re-closed if the fault still exists. They can be manually re-closed after rectifying the fault. • Also the MCB which has tripped due to over-load or short circuit can be readily identified as the dolly or toggle or operating knob automatically moves to the “OFF” position.
- 5. MCB 1. Cable terminals 2. Bi-metal thermo element 3. Contacts 4. Arc chamber 5. Solenoid 6. Operating handle 7. Din rail mounting.
- 6. MCB N ON 10 A MCB OFF
- 7. E INTRODUCTION L • An Earth Leakage Circuit Breaker is a safety device used in electrical installations with high earth impedance to prevent Shock. C • Many electrical installations have a relatively high earth impedance. These may be due to use of local earth rod to dry ground conditions. B • These installations have a major problem if no ELCB is used. During live to earth fault current,two conditions occur. Because earth impedance is high, 1. Not enough current exist to trip a fuse or circuit breaker, so condition persists uncleared indefinitely . 2. The high impedance earth can not keep the voltage of all exposed CPC connected metalwork to safe voltage all such metalwork may rise to close to live conductor voltage. TYPES OF ELCB: I. Voltage Operated:- They Provide a major advance in safety for mains electrical supplies with inadequate earth impedance. II. Current Operated:- They Provide protection against earth leakage, through the details & method of operation are different.
- 8. E L C B Neutral Phase P N
- 9. E L C B
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