ELECTRIC LOCO SHED n.c.r. KANPUR (an unit of indian government)

Submitted to: Mr. Md. Israr (SSE)

Submitted by: Mr. SACHIN SINGH M.P.E.C. KANPUR 1304620015

Project presentation on FAILURE OF FUSE & MCB

ELECTRIC LOCO SHED KANPUR

CONTENT• What is fuse• Different types of fuse• Fuse in electric loco• Different types of fuse in loco• Use of fuse in loco• Failure of fuse• Maintenance of fuse• Circuit breaker• Miniature circuit breaker• MCB working principle• MCB construction• Trip unit of MCB• Overload protection• Advantage & disadvantage of MCB• Characteristics of MCB

INTRODUCTIONo ESTABLISHMENTo The Electric Loco Shed, Kanpur was established in 1965 with the

Electrification of Mughalsarai-Kanpur section. The shed started functioning with a meager holding of 11 imported WAM-1 type locomotives for Passenger services.

o It’s main purpose is of maintenance of o WAP1,WAP4,WAP5,WAP7 ,WAG5, WAM4 engines.

o INITIAL COSTo Rs. 1.5 (IN CRORES)

o PRESENT LOCO HOLDINGo 201,(43-WAP4, 153-WAG7, 02-WAG-9 & 3-WAM4)

What is a fuse?

A fuse is a device that protects against damage from excessive current. It contains a short piece of wire made of an alloy that melts readily.

The flow of current through a fuse causes the wire to heat up and melts when excessive current passes through the fuse.

A burned-out fuse which is commonly called a "blown" fuse must be replaced for the circuit to function.

Different types of fuses

Blade Type Fuses

Glass Fuses

SMT Fuses

Bolt-In Fuses

FUSE IN ELECTRIC LOCO

NH fuses are types of electrical resistors used as sacrificial devices to protect electrical circuits in industrial related plant.

NH fuses are easily identified by their square or oblong bodies combined with blade style terminals.

Due to their larger body size they have higher ratings comprising of up to 1.25kA in sum total.

Different types of fuses in loco

Fuse used in electric locos are different types such as shown in figure. they are bigger in size heavier in weight as compared to normal fuse.

the construction of fuse is also different such as they are made up by molding the winding or made up by ceramics. they can survive for high voltage and high current.

the rating of fuse shown in figure is 1000V/1000A. the resistance of fuse are very small such as in milliohm. the resistance of fuse shown in figure is 0.0949mΩ/210C.

Use Of Fuse In Electric Loco The loco have six dc motor to run

these motor the dc supply is required. The loco have a pantograph which takes supply from the main line which is generally a 25Kv line.

A transformer is connected After the pantograph to step down the supply to probably 1000V.

A bridge rectifier is connected in the secondary side of the transformer. The bridge rectifier used diode to rectify the supply.

The maximum number of diode used

in rectifier is 28 & the minimum number of diode used is 12

The fuse are connected in parallel in each of diode to protect it from damage. They are connected in parallel of each diode. When a fault current occurs it diverted it due to its small resistance.

The anode & cathode are mentioned in the box. It is divided into two parts & diode is settled in between of the parts. The diode is works as a bridge in between them. The terminal of anode & cathode is as a blade type.

The given figure shows the diode which is used to rectify the AC supply into DC supply. They are circular in size & heavy in weight.

The anode & cathode are mentioned in the diode. They are not directly connected to the secondary side of transformer.

FAILURE OF FUSE

When the current due to fault is very heavier & crosses the rating of fuse then the fuse’s contact is opened up.

The fuse winding are in a box so a mentor is unable to see the fuse whether it us damage or not.

A indicator is holded upon the surface of fuse it is near the blade type terminals. When the fuse is blown out the red pin comes up which means the fuse is damaged.

The indicator is shown in the red circle of the given figure.

MAINTENANCE OF FUSE

When fuse is blown out the indicator indicates that by pin mounted on the surface of fuse. The pin comes outside the surface of fuse that means the fuse not more usable.

So for the safe drive of train that’s the equipments will not be damaged it has to replace by some another fuse. So maintenance of fuse is done by replacing it by another fuse.

The damaged fuse will not rectified again so that we can not use it again means when a fuse is damaged it can not be repaired by anyhow.

So the only thing which is possible is replacing that fuse by another new fuse.

What is a circuit breaker?A circuit breaker is

an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.

Miniature Circuit Breakers (MCB)As the name implies it is the miniature form of circuit

breaker.It can operated as an ordinary switch in

making/breaking the circuit on which it has been applied on.

It is easy to handle and provide complete safety to human beings.

They have vast range and small steps between rated current, allow cables to be utilized fully.

MCB Working Principle

There are two arrangement of operation of miniature circuit breaker. One due to thermal effect of over current and other due to electromagnetic effect of over current.

The thermal operation of miniature circuit breaker is achieved with a bimetallic strip whenever continuous over current flows through MCB, the bimetallic strip is heated and deflects by bending.

As this mechanical latch is attached with operating mechanism, it causes to open the miniature circuit breaker contacts. But during short circuit condition, sudden rising of electric current, causes electromechanical displacement of plunger associated with tripping coil or solenoid of MCB.

The plunger strikes the trip lever causing immediate release of latch mechanism consequently open the circuit breaker contacts.

This was a simple explanation of miniature circuit breaker working principle.

MCB Construction

Miniature circuit breaker construction is very simple, robust and maintenance free.

Generally an MCB is not repaired or maintained, it just replaced by new one when required.

A miniature circuit breaker has normally three main constructional parts.

3. Trip Unit Of MCB

The Trip Unit is the main part, responsible for proper working of miniature circuit breaker. Two main types of trip mechanism are provided in MCB.

A bimetal provides protection against over load current and an electromagnet provides protection against short-circuit current.

Overload protectionA bimetal strip is used: to protect the cable against overload symbol: principle of the bimetal: in a Multi 9 circuitbreaker

bimetal

tripping bar

bimetaltripping bar

screwcalibration

stripbraid

NC45 NC100 / NC125

Choosing a circuit breakerIn conclusion

A circuit breaker is determined by:• rating•breaking capacity•number of poles•Voltage•tripping curve•Standard•Frequency•type of load

Advantages of MCBIt automatically switches off the electrical

circuit during abnormal condition of the network means in over load condition as well as faulty condition.

The fuse does not sense but Miniature Circuit Breaker does it in more reliable way.

MCB is much more sensitive to over current than fuse.

Characteristics of MCB

Disadvantages of MCB

Rated current not more than 100 A.Trip characteristics normally not adjustable.Thermal or thermal-magnetic operation.

Only one disadvantage of MCB over fuse is that this system is more costlier than fuse unit system.

Thank you.