Measurement of efficiency of shunt and series motors. As you know that the construction of any type of dc motor is very similar to a dc generator. A 4 point starter protects the armature of a dc shunt motor or compound wound dc motor against the initially high starting current of the dc motor the 4 point starter has a lot of constructional and functional similarity to a 3 point starter, but this special device has an additional point and coil in its construction as the name suggests. Three point starter construction, working principle. The stater has 2 step resistor cutting with the help of. In a shunt motor, the field and armature windings are connected in parallel. Learners examine the operation of a dc shunt motor and its characteristics. The current controlling device is termed as a hand starter. The stater has 2 step resistor cutting with the help of timer type. A 3 point starter is a device that helps in the starting and running of a dc shunt motor or compound wound dc motor similar to a 4 point starter. Since load is very small in a shunt motor, armature current is also very low. These connections are in accordance with nema mg1 and american standards publication 06.
Draw a circuit diagram of a splitphase motor that has one capacitor which is permanently connected during operation. The main function of this machine is that we get mechanical energy from electrical energy. Automatic starters for shunt and compound motor prezi. A threepoint starter is an electrical device, used for starting as well as maintaining the dc shunt motor speed. Its speed is nearly constant, falling off as the load increases due to resistance drop and armature reaction. The compound motors are used where higher starting torque and fairly. A stab is shaped piece of metal that makes up a certain type of wound rotor. Here for starting the motor, the control arm is moved clockwise from its off position to the on position against the spring tension. Torque equation of dc motor for series, shunt and compound. A two point starter is used for starting dc motor which has the problem of overspeeding due to loss of lod from its shaft. C is applied to a shunt motor, the large inductive reactance of shunt winding will reduce the field current too much.
To control the speed of dc shunt motor using field control method. A 3 point starter is considered suitable for a shunt motors b. The connection of resistance in this circuit is in. Pdf 04 direct current motors hooman tavassoli academia. Speed control of dc shunt motor with field and armature. The decreasing torque vs speed is caused by the armature resistance voltage drop and armature reaction. A twopoint starter is used for starting dc motor which has the problem of overspeeding due to loss of lod from its shaft.
Start dc shunt motor with three point starter youtube. In addition to the same threepoints that were used with the threepoint starter. Working principle from the above circuit diagram, we can conclude that if we want to increase the speed of the shunt motor, we will vary the field resistance. This type of starter can be used for shunt and compound motors, and if the field is lost, the starter drops out, protecting the motor against runaway. The voltage supply in the circuit is straight across both the motor s windings. The electromagnet that holds the starter in the run position is in the field circuit. In shunt dc motor we connect the field winding in parallel with the armature winding and we have a good speed regulation and also low starting torque which makes this motor suitable for beltdriven applications in industrial and automotive applications. Whenever a dc motor starts it requires a current that is equal to 56 times its load current to start. When a shunt dc motor reaches its full speed, the armature current is directly related to the motor load.
In electrical terminology, a parallel connection is called shunt. The ratio of starting torque to fullload torque is least in cases of 31. Principle of operation of 3 point and 4 point starters, drum controller, constant. Figure 1216 diagram of a shunt motor connected to a reversing motor starter.
A starter circuit has to be designed for a 24hp, 250v and 80a dc shunt motor, such that the maximum. In a shunt motor, the field circuit is connected in parallel shunt with the. Some would argue that this is the case regardless, but in the case of a shuntwound motor, you have full torque ontap for the asking, plus decent noload stability. Dc shunt wound motor application and operation engineers. This contrasts with the series connection of a dc motor that provides a significant speed drop when there is an addition or reduction of load. A shuntwound motor is a dc motor in which the wound electromagnetic rotor field is in parallel not series with the armature. Purpose and working of three point starter in dc shunt motors. A dc motor, whose field winding is excited by the current produced by itself, is called selfexcited. The dc shunt motor is 120vdc with rated speed of 1800 revolutions per minute. Dc shunt motor armature the parallel combination of two windings is connected across a common dc power supply. Connected to the positive terminal of the power source 2. The starting handle is held in position by the novolt coil, marked nv, which automatically allows the starter to return to the off position if the supply fails.
What is a 3 point starter working and drawbacks circuit globe. Dc shunt motor, matlab simulink, starter subsystem. Purpose and working of three point starter in dc shunt motors duration. In this starter the drawbackdisadvantage of the threepoint starter is eliminated. This is also well known that the dc machines can be used as a generator as well as as a motor, their is the difference of operation in both case i. Types of dc motors dc motor are of 3 types they are 1. The shuntwound motor in this case the field is in parallel with the armature, as shown in figure 2, and the shunt motor is the standard type of d. And because of its wide range of application different functional types of dc motor are available in the market for specific requirements. Types of dc motor separately excited shunt series compound. In dc shunt motor the armature and field winding are connected in parallel across the supply voltage the resistance of the shunt winding. Figure 2 compound motor 3 point this arrangement is same as in the case of the shunt motor except for the series field included in the armature circuit. The no load current, voltage and shunt field current are noted. In the weakened condition a slight reduction in line voltage would further weaken the holding magnet, releasing the arm of the starter and thus disconnecting the motor from the line.
Well, its due to the presence of back emf e b, which plays a critical role in governing the operation of the motor. Mar 06, 2019 a 4 point starter protects the armature of a dc shunt motor or compound wound dc motor against the initially high starting current of the dc motor. Consider the air gap flux remains fixed at its value at no load. Calculate the induced voltage, the output power, the efficiency and the torque of the motor if the mechanical and the magnetic losses are 900. Three point manual dc motor starter circuit diagram. Unscheduled stoppages of the motor make the three point starter quite unpopular. To study the speed control of the given dc shunt motor by field control method and armature control method. The field rheostat of the motor is adjusted to bring the motor speed to the rated value. Dec 29, 2015 the shunt field windings of a dc shunt motor are made of smaller gauge wire, but they have many more turns than a serieswound dc motor. A shuntwound motor has decreasing torque as speed increases. A 3 point starter is considered suitable for a shunt. Oct 19, 2011 220v dc shunt motor has an armature resistance of 0. It is this undesirable feature of a threepoint starter which makes it unsuitable.
Finally, unless your budget cant afford it, never go with anything less than a 4quadrant dc drive controller. A 3 point starter is considered suitable for a shunt motors b shunt as well as compound motors c shunt, compound and series motors d all dc motors 29. The coil of the holding magnet is connected across the line when the arm is moved from the off position. The direct electric current motor or the dc motor has a lot of application in todays field of engineering and technology. The efficiency increases as the armature current is increased up to the point of. The shunt connected dc motor is selected because of its ability to maintain nearly uniform speed while carrying different loads. What is a dc shunt motor and its advantage and disadvantage. Title of the experiment page no 7 retardation test on dc shunt motor. To control the speed of dc shunt motor using armature control method. This kind of winding is called shunt winding and the motor shunt dc motor creation and principle of operation of a shunt dc motor is same as any other dc motor. Speed control of dc shunt motor with field and armature rheostat control 79 2. Rohit kumar 1 gives the study of different types of starters used in industries, i. This paper discusses the speed and torque control of a shunt dc motor through matlab simulink simulations.
The various applications of dc shunt motor are in lathe machines, centrifugal pumps, fans, blowers, conveyors, lifts, weaving machine, spinning machines, etc. Types of dc motor separately excited shunt series compound dc. Geethanjali college of engineering and technology department electrical and electronics engineering electrical machines i lab. Dc motor starters and their circuit diagram electrical. Use figure 2 if your motor has a dual voltage shunt field. As such, the field windings and armature are connected in a parallel combination, and in electrical terminology a parallel combination is known as a shunt.
In a shunt dc motor, the armature and field windings are linked in parallel. As resistance increased, the value of the field current will reduce. Equivalent circuit parameters are armature resistance ra 110 ohms, field resistance rf 2. The shunt motors are used where constant speed is required and starting conditions are not severe.
Nov 09, 2015 a two point starter is used for starting dc motor which has the problem of overspeeding due to loss of lod from its shaft. Dec 11, 2016 history of dc motor michael faraday u. The tapping points of the starting resistance are brought out to a. Once the motor reaches its full speed, it remains constant. The hhandle in the circuit is held in run condition with an electromagnet strengthened by an nvc no volt trip coil. Applications of dc machines motors and generators circuit. It is so called because it has three terminals l, f and a. Precaution the field rheostat should be kept at minimum resistance position. Starting from an electric shaver to parts of automobiles, in all small or medium sized motoring applications dc motors come handy.
This paper explains the need for a starter in dc shunt motor. This video will give you a brief introduction about the dc shunt motor, the need for three point starters, its working and also about the purpose of nvc and olrs in 3 point starter. Starters for the dc shunt wound and compound wound motors. I have to offer dc starter for 8kw dc shunt motor at 220 vdc. The shuntconnected dc motor is selected because of its ability to maintain nearly uniform speed while carrying different loads. Use figure 1 if your motor has a single voltage shunt field.
What is a 3 point starter working and drawbacks circuit. Purpose and working of three point starter in dc shunt. Hence torque developed by a dc motor is directly proportional to the flux per pole and the. The overload relay will operate when the armature current exceeds the limit. A shuntwound dc motor has a decreasing torque when speed increases.
The high number of turns allows a strong magnetic field to be generated, but the smaller gauge wires provide a high resistance and limit the current flowing through the shunt coil. Diagram and working principle march 6, 2019 february 24, 2012 by electrical4u a 3 point starter is a device that helps in the starting and running of a dc shunt motor or compound wound dc motor similar to a 4 point starter. In case the conditions for maximum power for a dc motor are established, the efficiency of the motor will be 30. A good material for the poles of a pmdc motor should have the apposite of the above. Speed of a shunt dc motor can be easily controlled. On the other hand, back emf reduces marginally more than that the. The 4 point starter has a lot of constructional and functional similarity to a 3 point starter, but this special device has an additional point and coil in its construction as the name suggests. Construction and operation of four point starter a 4 point starter as the name suggests has 4 main operational points, namely 1. A shunt excited dc motors terminal voltage is 500 v. Starting the principle of starting a shunt motor will be seen from figure 4 which shows the faceplate type starter, the starting resistance being in between the segments marked 1, 2, 3, etc. Whenever the shunt motor load is increased e b vi a r a and flux reduces as a result drop in the armature resistance and armature reaction. A shunt wound dc motor has a decreasing torque when speed increases. Consequently, shunt motor will not usually run on a.
Dc motor starting, two and three point starter the. Lathes, drills, boring mills, shapers, spinning, and weaving machines series motor. Feb 03, 2018 working of dc motor with three point starter. Hence the armature current differs and the speed of a dc shunt motor will continue constant which is shown in the fig dotted line ab. A 3point starter is considered suitable for a shunt motors b shunt as well as compound motors c shunt, compound and series motors d all dc motors 29. The 3 point starter connects the resistance in series with the circuit which reduces the high starting current and hence protects the machines from damage. Speed control method of dc series motor shubham sharma, simran singh oberoi, siddharth nair ece dept, dronacharya college of engg. The shunt winding has a large number of turns so that it has appreciable inductance. Figure 3 shunt motor 4 point this is a connection diagram of a 4 point starter with a shunt motor. In case of a shunt wound dc motor or more specifically shunt wound self excited dc motor, the field windings are exposed to the entire terminal voltage as they are connected in parallel to the armature winding as shown in the figure below.
A 3 point starter is a device that helps in the starting and running of a dc shunt motor or compound wound dc motor similar to a 4 point starter now the question is why these types of dc motors require the assistance of the starter in the first place. The characteristics of a shunt motor reveal that it is an approximately constant speed motor. The shunt field windings of a dc shunt motor are made of smaller gauge wire, but they have many more turns than a serieswound dc motor. Thus it is required to reduce the voltage when the motor starts. Dc shunt wound motor application and operation engineers edge. Speed control of dc shunt motor by armature and field control.
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