motorized ramming machine

8/9/2019 Motorized Ramming Machine

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MOTORIZED RAMMING MACHINE

CHAPTER-1

INTRODUCTION

Here we fabricate the model for ramming machine it is used to set the loose

sand in foundries. It minimizes the work load of man power. Mostly ramming

machines are using the vibrating table with the arrangement of zigzag movement and

it needs more current to carry out this process. To avoid this we are using cam with

return spring arrangement for the ramming machine. The project consists of the

following parts ramming tool, eturn spring, Handle with screw rod, !am

arrangement and Motor with worm gear arrangement. " sand rammer is a piece of

e#uipment used in foundry sand testing to make test specimen of molding sand by

compacting bulk material by free fi$ed height drop of fi$ed weight for % times. It is

also used to determine compatibility of sands by using special specimen tubes and a

linear scale.

Mechanism

&and rammer consists of calibrated sliding weight actuated by cam, a shallow cup to

accommodate specimen tube below ram head, a specimen stripper to strip compacted

specimen out of specimen tube, a specimen tube to prepare the standard specimen of

'( mm diameter by '( mm height or ) inch diameter by ) inch height for an "*&

standard specimen.

Specimen Preparati n

The cam is actuated by a user by rotating the handle, causing a cam to lift the

weight and let it fall freely on the frame attached to the ram head. This produces a

standard compacting action to a pre+measured amount of sand. ariety of standard

specimen for -reen &and and &ilicate based !/ ) 0 sand are prepared using a sand

rammer along with accessories

Specimen T!pe " sand

D.D.C.S.M. POLYTECHNIC, MECHANICAL ENGG. Page


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!ompression !ylindrical0 -reen &and and &ilicate based sand

Tensile &pecimen &ilicate based sand

Transverse &pecimen &ilicate based sand

The object for producing the standard cylindrical specimen is to have the

specimen become ) inches high plus or minus 12%) inch0 with three rams of the

machine. "fter the specimen has been prepared inside the specimen tube, the

specimen can be used for various standard sand tests such as the permeability test, the

green sand compression test, the shear test, or other standard foundry tests. The sand

rammer machine can be used to measure compactability of prepared sand by filling

the specimen tube with prepared sand so that it is level with the top of the tube. The

tube is then placed under the ram head in the shallow cup and rammed three times.

!ompactability in percentage is then calculated from the resultant height of the sand

inside the specimen tube. " rammer is mounted on a base block on a solid foundation,

which provides vibration damping to ensure consistent ramming.

Prere#$isites%

3rere#uisite e#uipments for sand rammer may vary from case to case basis or testingscenario4Case 1 4 If the prepared sand is ready

Tube filler accessory to fill sample tube with sand. "dvantage is it lets the sandfill in from fi$ed distance and riddles it before filling.

Case &% 5$periment by preparing new sand sample If sand needs to be prepared before making specimen following e#uipments may be needed

6aboratory sand muller or laboratory sand mi$er for core sands0

Case '% *or low compressive strength sands and mi$tures4

&plit specimen tube

CHAPTER-&



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reduces the ramming time and labor. 9ue to this the cost is reduced considerable. &o this machine finds

application in foundries. ).

The rammer can be handled by an operator without feeling uneasiness. ;o separate skill is re#uiredto operate this rammer. The operation is #uick and hence it is a time saving one. The operation is easy and

consumes less cost. 9ue to the above reasons it finds its e$tensive application in manufacturing industries. It

has an e$tensive application in both large scale and small scale industries because of its economy and easy

handling

"utomation can be achieved through computers, hydraulics, pneumatics,

robotics, etc., of these sources, pneumatics form an attractive medium for low cost automation. The

main advantages of all pneumatic systems are economy and simplicity. "utomation plays an important role

in mass production. ;owadays almost all the manufacturing process is being atomized in order to deliver

the products at a faster rate. The rammer can be handled by an operator without feeling

uneasiness. ;o separate skill is re#uired to operate this rammer. The operation is #uick

and hence it is a time saving one. The operation is easy and consumes less cost. 9ue to

the above reasons it finds its e$tensive application in manufacturing industries.

It has an e$tensive application in both large scale and small scale industries because of

its economy and easy handling.

&trength uniform ramming of sand is obtained by this rammer. The time consumption for ramming is reduced greatly. &killed labor is not re#uired. 5asy operation It can be transported easily from one place to another since dismantling and

assembling is simple.

It reduces more labor for ramming operation. Maintenance is easy.


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reduction of production time and elimination of more labor for ramming operation

reduce production cost, thereby the economy is greatly achieved.

CHAPTER-'

S*STEM ,UNCTION

OR+ING PRINCIP(E%

Here we are using the table with the support of return spring arrangement

and below of this we are placing the cam mechanism with rotation movement.

The rotation movement for cam is given by the motor with worm gear

arrangement for the vibrating operation. The supporting shaft on either side of

the table holds the molding bo$ preventing it from falling while the operation

takes place. The motor will rotate the worm gear arrangement and that will

rotate the cam mechanism hence the table moves up and down. The ramming



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tool is rotated by means of handle to seat on the molding sand and to set the

sand firmly in the molding bo$.

AD)ANTAGES

-et good output

5asy to operate

5asy to maintain

DISAD)ANTAGES

;ut should be tightened every time manually

APP(ICATION

It is applicable in foundries.

INDUSTRIA( APP(ICATION O, RAMMING

The rammer can be handled by an operator without feeling uneasiness. ;o

separate skill is re#uired to operate this rammer. The operation is #uick and hence it is

a time saving one. The operation is easy and consumes less cost. 9ue to the above

reasons it finds its e$tensive application in manufacturing industries. It has an

e$tensive application in both large scale and small scale industries because of its

economy and easy handling.

The manufacturing operation is being atomized for the following reasons.

To achieve mass production

To reduce man power

To increase the efficiency of the plant

To reduce the work load

To reduce the production cost

To reduce the production time

To reduce the material handling



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To reduce the fatigue of workers

To achieve good product #uality

6ess maintenance

CHAPTER-.

/ASIC MOTOR THEOR*

Intr d$cti n

It has been said that if the "ncient omans, with their advanced civilization

and knowledge of the sciences, had been able to develop a steam motor, the course of

history would have been much different. The development of the electric motor in

modern times has indicated the truth in this theory. The development of the electric

motor has given us the most efficient and effective means to do work known to man.

8ecause of the electric motor we have been able to greatly reduce the painstaking toil

of man=s survival and have been able to build a civilization which is now reaching to

the stars. The electric motor is a simple device in principle. It converts electric energyinto mechanical energy. /ver the years, electric motors have changed substantially in

design, however the basic principles have remained the same. In this section of the

"ction -uide we will discuss these basic motor principles. >e will discuss the

phenomena of magnetism, "! current and basic motor operation.

Ma0netism

;ow, before we discuss basic motor operation a short review of magnetism

might be helpful to many of us. >e all know that a permanent magnet will attract and

hold metal objects when the object is near or in contact with the magnet. The

permanent magnet is able to do this because of its inherent magnetic force which is

referred to as a ?magnetic field?. In *igure 1 , the magnetic field of two permanent

magnets are represented by ?lines of flu$?. These lines of flu$ help us to visualize the

magnetic field of any magnet even though they only represent an invisible phenomena. The number of lines of flu$ vary from one magnetic field to another. The



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stronger the magnetic field, the greater the number of lines of flu$ which are drawn to

represent the magnetic field. The lines of flu$ are drawn with a direction indicated

since we should visualize these lines and the magnetic field they represent as having a

distinct movement from a ;+pole to a &+pole as shown in *igure 1. "nother butsimilar type of magnetic field is produced around an electrical conductor when an

electric current is passed through the conductor as shown in *igure )+a. These lines of

flu$ define the magnetic field and are in the form of concentric circles around the

wire. &ome of you may remember the old ?6eft Hand ule? as shown in *igure )+b.

The rule states that if you point the thumb of your left hand in the direction of the

current, your fingers will point in the direction of the magnetic field.

Figure 1 - The lines of flux of a magnetic field travel from the N-pole to the S-pole.



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Figure 2 - The flow of electrical current in a conductor sets up concentric lines of

magnetic flux around the conductor.

Figure 3 - The magnetic lines around a current carrying conductor leave from the N-

pole and re-enter at the S-pole.

>hen the wire is shaped into a coil as shown in *igure %, all the individual flu$

lines produced by each section of wire join together to form one large magnetic field

around the total coil. "s with the permanent magnet, these flu$ lines leave the north of

the coil and re+enter the coil at its south pole. The magnetic field of a wire coil is

much greater and more localized than the magnetic field around the plain conductor

before being formed into a coil. This magnetic field around the coil can be

strengthened even more by placing a core of iron or similar metal in the center of the

core. The metal core presents less resistance to the lines of flu$ than the air, thereby



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causing the field strength to increase. This is e$actly how a stator coil is made@ a coil

of wire with a steel core.0 The advantage of a magnetic field which is produced by a

current carrying coil of wire is that when the current is reversed in direction the poles

of the magnetic field will switch positions since the lines of flu$ have changeddirection. This phenomenon is illustrated in *igure A. >ithout this magnetic

phenomenon e$isting, the "! motor as we know it today would not e$ist.

Figure - The poles of an electro-magnetic coil change when the direction of current

flow changes.

Ma0netic Pr p$ si n 2ithin a M t r



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Figure ! Magnetic 3ropulsion within a Motor

The basic principle of all motors can easily be shown using two electromagnets

and a permanent magnet. !urrent is passed through coil no. 1 in such a direction that a

north pole is established and through coil no. ) in such a direction that a south pole is

established. " permanent magnet with a north and south pole is the moving part of this

simple motor. In *igure '+a the north pole of the permanent magnet is opposite the

north pole of the electromagnet. &imilarly, the south poles are opposite each other.

6ike magnetic poles repel each other, causing the movable permanent magnet to begin

to turn. "fter it turns part way around, the force of attraction between the unlike poles

becomes strong enough to keep the permanent magnet rotating. The rotating magnetcontinues to turn until the unlike poles are lined up. "t this point the rotor would

normally stop because of the attraction between the unlike poles. *igure '+b0

If, however, the direction of currents in the electromagnetic coils was suddenly

reversed, thereby reversing the polarity of the two coils, then the poles would again be

opposites and repel each other. *igure '+c0. The movable permanent magnet would

then continue to rotate. If the current direction in the electromagnetic coils waschanged every time the magnet turned 1B( degrees or halfway around,then the magnet

would continue to rotate. This simple device is a motor in its simplest form. "n actual

motor is more comple$ than the simple device shown above, but the principle is the

same.

AC C$rrent

How the current is reversed in the coil so as to change the coils polarity, you

ask. >ell, as you probably know, the difference between 9! and "! is that with 9!

the current flows in only one direction while with "! the direction of current flow

changes periodically. In the case of common "! that is used throughout most of the


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vary in #uantity. >e can have a ' amp, 1( amp or 1(( amp flow for instance. >ith

pure 9!, this means that the current flow is actually ',1(, or 1(( amps on a

continuous basis. >e can visualize this on a simple time+current graph by a straight

line as shown in *igure :.

Figure " - #isuali$ation of %&

8ut with "! it is different. "s you can well imagine, it would be rather difficult for

the current to be flowing at say 1(( amps in a positive direction one moment and then

at the ne$t moment be flowing at an e#ual intensity in the negative direction. Instead,

as the current is getting ready to change directions, it first tapers off until it reaches

zero flow and then gradually builds up in the other direction. &ee *igure C. ;ote that

the ma$imum current flow the peaks of the line0 in each direction is more than the

specified value 1(( amps in this case0. Therefore, the specified value is given as an

average. It is actually called a ?root mean s#uare? value, but don=t worry about

remembering this because it is of no importance to us at this time. >hat is important

in our study of motors, is to realize that the strength of the magnetic field produced by

an "! electro+magnetic coil increases and decreases with the increase and decrease of

this alternating current flow.

/asic AC M t r Operati n

"n "! motor has two basic electrical parts4 a ?stator? and a ?rotor? as shown in

*igure B. The stator is in the stationary electrical component. It consists of a group of

individual electro+magnets arranged in such a way that they form a hollow cylinder,

with one pole of each magnet facing toward the center of the group. The term, ?stator?



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is derived from the word stationary. The stator then is the stationary part of the motor.

The rotor is the rotating electrical component. It also consists of a group of electro+

magnets arranged around a cylinder, with the poles facing toward the stator poles.

Figure ' - #isuali$ation of (&.

The rotor, obviously, is located inside the stator and is mounted on the motor=s

shaft. The term ?rotor? is derived from the word rotating. The rotor then is the rotating

part of the motor. The objective of these motor components is to make the rotor rotate

which in turn will rotate the motor shaft. This rotation will occur because of the

previously discussed magnetic phenomenon that unlike magnetic poles attract each

other and like poles repel. If we progressively change the polarity of the stator poles in

such a way that their combined magnetic field rotates, then the rotor will follow and

rotate with the magnetic field of the stator.



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Figure ) - *asic electrical components of an (& motor.

This ?rotating magnetic fields of the stator can be better understood by

e$amining *igure D. "s shown, the stator has si$ magnetic poles and the rotor has two

poles. "t time 1, stator poles "+1 and !+) are north poles and the opposite poles, "+)

and !+1, are south poles. The &+pole of the rotor is attracted by the two ;+poles of the

stator and the ;+pole of the rotor is attracted by the two south poles of the stator. "t

time ), the polarity of the stator poles is changed so that now !+) and 8+1 and ;+poles

and !+1 and 8+) are &+poles. The rotor then is forced to rotate :( degrees to line up

with the stator poles as shown. "t time %, 8+1 and "+) are ;. "t time A, "+) and !+1

are ;. "s each change is made, the poles of the rotor are attracted by the opposite poles on the stator. Thus, as the magnetic field of the stator rotates, the rotor is forced

to rotate with it.



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Figure + - The rotating magnetic field of an (& motor.

/ne way to produce a rotating magnetic field in the stator of an "! motor is to

use a three+phase power supply for the stator coils. >hat, you may ask, is three+phase

powerE The answer to that #uestion can be better understood if we first e$amine

single+phase power. *igure C is the visualization of single+phase power. Theassociated "! generator is producing just one flow of electrical current whose

direction and intensity varies as indicated by the single solid line on the graph. *rom

time ( to time %, current is flowing in the conductor in the positive direction. *rom

time % to time :, current is flowing in the negative. "t any one time, the current is only

flowing in one direction. 8ut some generators produce three separate current flows

phases0 all superimposed on the same circuit. This is referred to as three+phase power.

"t any one instant, however, the direction and intensity of each separate current flow

are not the same as the other phases. This is illustrated in *igure 1(. The three separate

phases current flows0 are labeled ", 8 and !. "t time 1, phase " is at zero amps,

phase 8 is near its ma$imum amperage and flowing in the positive direction, and

phase ! is near to its ma$imum amperage but flowing in the negative direction. "t

time ), the amperage of phase " is increasing and flow is positive, the amperage of

phase 8 is decreasing and its flow is still negative, and phase ! has dropped to zero

amps. " complete cycle from zero to ma$imum in one direction, to zero and to



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ma$imum in the other direction, and back to zero0 takes one complete revolution of

the generator. Therefore, a complete cycle, is said to have %:( electrical degrees. In

e$amining *igure 1(, we see that each phase is displaced 1)( degrees from the other

two phases. Therefore, we say they are 1)( degrees out of phase.

Figure 1, - The pattern of the separate phases of three-phase power.

To produce a rotating magnetic field in the stator of a three+phase "! motor, all

that needs to be done is wind the stator coils properly and connect the power supply

leads correctly. The connection for a : pole stator is shown in *igure 11. 5ach phase

of the three+phase power supply is connected to opposite poles and the associated

coils are wound in the same direction. "s you will recall from *igure A, the polarity of

the poles of an electro+magnet are determined by the direction of the current flowthrough the coil. Therefore, if two opposite stator electro+magnets are wound in the

same direction, the polarity of the facing poles must be opposite. Therefore, when pole

"1 is ;, pole ") is &. >hen pole 81 is ;, 8) is & and so forth.



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Figure 11 - ethod of connecting three-phase power to a six-pole stator.

*igure 1) shows how the rotating magnetic field is produced. "t time1, the

current flow in the phase ?"? poles is positive and pole "+1 is ;. The current flow in

the phase ?!? poles is negative, making !+) a ;+pole and !+1 is &. There is no current

flow in phase ?8?, so these poles are not magnetized. "t time ), the phases have

shifted :( degrees, making poles !+) and 8+1 both ; and !+1 and 8+) both &. Thus,

as the phases shift their current flow, the resultant ; and & poles move clockwise

around the stator, producing a rotating magnetic field. The rotor acts like a bar

magnet, being pulled along by the rotating magnetic field.



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Figure 12 - ow three-phase power produces a rotating magnetic field.


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This is no e$ternal power supply. "s you might imagine from the motor=s name,

an induction techni#ue is used instead. Induction is another characteristic of

magnetism. It is a natural phenomena which occurs when a conductor aluminum bars

in the case of a rotor, see *igure 1%0 is moved through an e$isting magnetic field or when a magnetic field is moved past a conductor. In either case, the relative motion of

the two causes an electric current to flow in the conductor. This is referred to as

?induced? current flow. In other words, in an induction motor the current flow in the

rotor is not caused by any direct connection of the conductors to a voltage source, but

rather by the influence of the rotor conductors cutting across the lines of flu$ produced

by the stator magnetic fields. The induced current which is produced in the rotor

results in a magnetic field around the rotor conductors as shown in *igure 1A. This

magnetic field around each rotor conductor will cause each rotor conductor to act like

the permanent magnet in the *igure D e$ample. "s the magnetic field of the stator

rotates, due to the effect of the three+phase "! power supply, the induced magnetic

field of the rotor will be attracted and will follow the rotation. The rotor is connected

to the motor shaft, so the shaft will rotate and drive the connection load. That=s how a

motor worksF &imple, was it notE



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Figure 1 - ow voltage is induced in the rotor0 resulting in current flow in the rotor

conductors.

CHAPTER-3

PO ER SUPP(* UNIT

/(OC+ DIAGRAM%

CIRCUIT DIAGRAM



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Descripti n

"! power is easily in bulk from through different methods, but generally for

many power control circuits and other industrial application 9! power is very much

re#uired. Hence "! power necessarily has to be converted into 9! power by means

of electronic rectifier, which is simpler, cheaper, and highly efficient compared to

rotary converters or 9! generators.

The Grecti"ier is a circuit, which converts "! oltage and currents into

pulsating 9! voltages and currents. It consists of 9! components and the unwanted

ac ripple or harmonic components, which can be removed by using filter circuit. Thus

the output obtained will be steady 9! voltage and magnitude of 9! voltage can be

varied by varying the magnitude of "! oltage.

ectifiers are grouped into two categories depending on the period of conduction. a0 Half >ave ectifier b0 *ull >ave ectifier.

In this power supply unit we are using *ull+>ave ectifier.

,$ - a4e Recti"ier

" Gfull wave rectifier is one which converts "! voltage into a pulsating 9!

voltage using both half+cycles of the applied input voltage. It typically uses two

diodes, one of which conducts and provides output during one half+cycle i.e.,

positive2negative0 and other diode conducts during the other half+cycle i.e.

negative2positive0.

,i ters

It is a circuit, which removes, ripples unwanted ac components0 present in the

pulsating dc voltage.



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Re0$ at r

It is a circuit which maintains the terminal voltage as constant even if the input

voltage varies or load current varying.

*ull wave rectifier rectifies the full cycle in the waveform i.e. it rectifies both the

positive and negative cycles in the waveform. >e have already seen the

characteristics and 2 r5in0 " Ha " a4e Recti"ier . This *ull wave rectifier has an

advantage over the half wave i.e. it has average output higher than that of half wave

rectifier. The number of "! components in the output is less than that of the input.

The full wave rectifier can be further divided mainly into following types.

1. !enter Tapped *ull >ave ectifier

). *ull >ave 8ridge ectifier

Center Tapped ,$ a4e Recti"ier%

!enter tap is the contact made at the middle of the winding of the transformer.

Center Tapped ,$ a4e Recti"ier Circ$it Dia0ram

In the center tapped full wave rectifier two diodes were used. These are connected to

the center tapped secondary winding of the transformer. "bove circuit diagram shows

the center tapped full wave rectifier. It has two diodes. The positive terminal of two



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diodes is connected to the two ends of the transformer. !enter tap divides the total

secondary voltage into e#ual parts.

Center Tapped Full Wave Rectifier Working:

The primary winding of the center tap transformer is applied with the "c

voltage. Thus the two diodes connected to the secondary of the transformer conducts

alternatively. *or the positive half cycle of the input diode 91 is connected to the

positive terminal and 9) is connected to the negative terminal. Thus diode 91 is in

forward bias and the diode 9) is reverse biased. /nly diode 91 starts conducting and

thus current flows from diode and it appears across the load 6. &o positive cycle of

the input is appeared at the load.

9uring the negative half cycle the diode 9) is applied with the positive cycle.

9) starts conducting as it is in forward bias. The diode 91 is in reverse bias and this

does not conduct. Thus current flows from diode 9) and hence negative cycle is also

rectified, it appears at the load resistor 6.

8y comparing the current flow through load resistance in the positive and

negative half cycles, it can be concluded that the direction of the current flow is same.

Thus the fre#uency of rectified output voltage is two times the input fre#uency. The

output that is rectified is not pure, it consists of a dc component and a lot of ac

components of very low amplitudes.

Peak Inverse Voltage (PIV) of Centre Tap Full Wave Rectifier:

3I is defined as the ma$imum possible voltage across a diode during its

reverse bias. 9uring the first half that is positive half of the input, the diode 91 is

forward bias and thus conducts providing no resistance at all. Thus, the total voltage

s appears in the upper+half of the ac supply, provided to the load resistance .

&imilarly, in the case of diode 9) for the lower half of the transformer total secondary

voltage developed appears at the load. The amount of voltage that drops across the

two diodes in reverse bias is given as

3I of 9) m J m ) m



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3I of 91 ) m

m is the voltage developed across upper and lower halves.

Pea5 C$rrent%

The peak current is the instantaneous value of the voltage applied to the rectifier. It

can be written as

s sm &inwt

6et us assume that the diode has a forward resistance of * ohms and a reverse

resistance is e#ual to infinity, thus current flowing through the load resistance 6 isgiven as

Im sm 2 , J 60

O$tp$t C$rrent%

&ince the current is same through the load resistance 6 in the two halves of

the ac cycle, magnitude of dc current Idc, which is e#ual to the average value of ac

current, can be obtained by integrating the current i1 between ( and pi or current i)

between pi and )pi.



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Trans" rmer Uti i6ati n ,act r%

This can be calculated by considering primary and secondary windings

separately. Its value is (.:D%.This can be used to determine transformer secondary

rating.



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INPUT AND OUTPUT A)E,ORM O, ,U(( A)E RECTI,IER



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CHAPTER-7

COMPONENT DETAI(S

6.1 12V DC GEARED MOTOR:

Descripti n%

The 1) 9! -eared Motor can be used in variety of robotics applications and

is available with wide range of 1( 3M.

Speci"icati n%


8 6ength4 B(mm

8 Tor#ue4 1.' kg.cm

8 &haft 9iameter4 :mm

8 >eight4 1%(.((g


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" resist r is a two+terminal electronic component having a resistance 0 that

produces a voltage 0 across its terminals that is proportional to the electric current

I0 flowing through it in accordance with /hm=s law4

V : IR

esistors are elements of electrical networks and electronic circuits and are

ubi#uitous in most electronic e#uipment. 3ractical resistors can be made of various

compounds and films, as well as resistance wire wire made of a high+resistivity alloy,

such as nickel+chrome0. The primary characteristics of a resistor are the resistance, the

tolerance, the ma$imum working voltage and the power rating. /ther characteristics

include temperature coefficient, noise, and inductance. 6ess well+known is critical

resistance, the value below which power dissipation limits the ma$imum permitted

current, and above which the limit is applied voltage. !ritical resistance is determined

by the design, materials and dimensions of the resistor. esistors can be integrated into

hybrid and printed circuits, as well as integrated circuits. &ize, and position of leads

or terminals0, are relevant to e#uipment designers@ resistors must be physically large

enough not to overheat when dissipating their power.

RESISTOR )A(UE IDENTI,ICATION%

;C r c din0 meth dinding resistance dominates

load losses, whereas hysteresis and eddy currents losses contribute to over DDK of the

no+load loss. The no+load loss can be significant, so that even an idle transformer

constitutes a drain on the electrical supply and a running cost. 9esigning transformers



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for lower loss re#uires a larger core, good+#uality silicon steel, or even amorphous

steel for the core and thicker wire, increasing initial cost so that there is a trade+off

between initial costs and running cost also see energy efficient transformer0.

Transformer losses are divided into losses in the windings, termed copper loss, andthose in the magnetic circuit, termed iron loss. 6osses in the transformer arise from4

indin0 resistance

!urrent flowing through the windings causes resistive heating of the

conductors. "t higher fre#uencies, skin effect and pro$imity effect create

additional winding resistance and losses.

H!steresis sses

5ach time the magnetic field is reversed, a small amount of energy is lost due

to hysteresis within the core. *or a given core material, the loss is proportional

to the fre#uency, and is a function of the peak flu$ density to which it is

subjected.

Edd! c$rrents

*erromagnetic materials are also good conductors and a core made from such a

material also constitutes a single short+circuited turn throughout its entire

length. 5ddy currents therefore circulate within the core in a plane normal to

the flu$, and are responsible for resistive heating of the core material. The eddy

current loss is a comple$ function of the s#uare of supply fre#uency and

inverse s#uare of the material thickness.LAA

5ddy current losses can be reduced by making the core of a stack of plates electrically insulated from each other,

rather than a solid block@ all transformers operating at low fre#uencies use

laminated or similar cores.

Ma0net stricti n



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Iron losses are caused mostly by hysteresis and eddy current effects in the core,

and are proportional to the s#uare of the core flu$ for operation at a given fre#uency.

&ince the core flu$ is proportional to the applied voltage, the iron loss can be

represented by a resistance ! in parallel with the ideal transformer.

" core with finite permeability re#uires a magnetizing current I m to maintain

the mutual flu$ in the core. The magnetizing current is in phase with the flu$.

&aturation effects cause the relationship between the two to be non+linear, but for

simplicity this effect tends to be ignored in most circuit e#uivalents. >ith a sinusoidal

supply, the core flu$ lags the induced 5M* by D(W and this effect can be modeled as a

magnetizing reactance reactance of an effective inductance0 m in parallel with thecore loss component. c and m are sometimes together termed the magneti$ing

4ranch of the model. If the secondary winding is made open+circuit, the current 5 (

taken by the magnetizing branch represents the transformer=s no+load current.

The secondary impedance s and s is fre#uently moved or ?referred?0 to the

primary side after multiplying the components by the impedance scaling factor

N p2 N s0)

.

The resulting model is sometimes termed the ?e$act e#uivalent circuit?, though

it retains a number of appro$imations, such as an assumption of linearity. "nalysis

may be simplified by moving the magnetizing branch to the left of the primary

impedance, an implicit assumption that the magnetizing current is low, and thensumming primary and referred secondary impedances, resulting in so+called



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@91 DIMENSION%

@9&COST ESTIMATION



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S9 N Partic$ ars C st

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) /ther !omponents s. %(((.((

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53/53

L1 . 9esign data book+ 3.&.-. Tech.

L) . 3neumatic hand book+ .H.>arrning i. Machine tool design hand book !entral

machine tool Institute, ii. 8angalore.L% . &trength of materials+ .&.Uurmi

LA . Manufacturing Technology+ M.Haslehurst

motorized ramming machine

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