Premier trading corporation 1 speed control of dc motor shunt type aim a to study the speed control of dc motor below the normal range by armature. The dc shuntwound motor, running on direct current, has its field windings placed in parallel to the armature. Advantages and disadvantages of dc shunt motor load answers. This reduction in the counter emf or the back emf e b results in the increase of the net voltage. The compound motor responds better to heavy load changes than a shunt motor because of the increased current through the series field coils. In this method, the dc machine generator or motor is run as a motor at noload and losses of the machine are determined. Testing of dc motor, dc motor testing direct and indirect. Then, knowing the armature and shunt cu losses at a given load current, efficiency can be calculated. This means that the shunt motor has very low starting torque, which requires that the shaft load be rather small. N, given by, this can be graphically explained below. In this article we are going to discuss about brake test on d. This article mainly deals with the determination of the efficiency curve. Shunt wound dc motor or dc shunt motor is a selfexcited dc motor whereas we said before at previous article types of dc motor that it operates on direct current and the field winding is connected in parallel to the armature winding so both windings exposed to the same power supply voltage, and this motor able to maintain at a.
Load characteristics of dc compound generator with differential and cumulativeconnections. Applications that meet these criteria and are suitable for dc shunt motors include machines tool such. Keep in mind, however, that they cannot produce high starting torque, so the load at startup must be small. The dc shunt motor is 120vdc with rated speed of 1800 revolutions per minute.
To determine the efficiency of the given dc shunt motor by conducting load test. Feb 22, 2018 load test is performed on all motors for the common purpose of determining the efficiency of the motor. The machine under test is speeded up slightly beyond its normal speed and then supply is cut. It is a no load test and therefore cannot be performed on a dc series motor. At the very onset of load introduction to a shunt wound dc motor, the speed definitely reduces, and along with speed also reduces the back emf, e b. To find the various parameters such as torque, input power, output power etc. As the test is on no load, it is impossible to know whether commutation would be satisfactory at full load and whether the temperature rise would be within the specified limits. The power required to test a large machine is small. We believe that these faqs will be useful for your practical exams and interviews as well. Retardation or running down test this method is applicable to shunt motors and generators and is used for finding stray losses. In this method, we find the mechanical friction and windage and iron losses of the machine. The primary and secondary windings are placed one over the other, placing lowvoltage winding nearer the core, whereas in sandwichtype winding ht and lt windings. May 30, 2017 it is an attempt to explain the experiment of load test on dc shunt motor in tamil by dr. There are several tests that are conducted for testing a dc machine generator or motor to judge its performance.
In swinburnes test the shunt motor is run on noload with rated voltage v applied to the terminals. If a dc generator delivers 180 w to a load, what is the minimum mechanical power in watts. If you are looking for job then go check out interview questions page to. The coils in the shunt field are composed of many turns of small wire, resulting in low shunt field current and moderate armature current. It is, therefore, apparent that the shunt motor should run at a reasonably constant speed. In a shunt motor, the field winding, as we ll as the armature winding, is connected in parallel shunt directly to the dc supply lines. Dc shunt motor theory quiz questions electrical practice tests. This test is applicable to those machines in which flux is practically constant i. Load characteristics of dc shunt and compound motor. If a dc generator delivers 180 w to a load, what is.
Construction and principle of operation of the shunt dc motor. As the constant loss is known the efficiency can be predetermined at any load. This test can be done in your own workshop using simple hand tools and a specialized electric testing device. Testing of dc machines can be broadly classified as. This boosts the field strength, providing added torque and speed. It is a simple method in which no load dc machine losses are measured seperately and from this the efficiency at any desired load can be. The most important performance tests to be conducted on the dc machine are.
Shunt dc motor the shunt motor is probably the most common dc motor used in industry today. State two ways by which the output polarity of a separatelyexcited dc shunt generator can be changed 2. Open circuit and load characteristics of dc shunt generatorcritical resistance and critical speed. This is the best and simplest method to find the efficiency of a constantspeed dc machine e. Just like most energy conversion devices, the dc shunt motor is not 100% efficient. Load characteristics of dc compound generator with differential and cumulative connection. The connection diagram for dc shunt machine is shown in the figure below. This is the complete theory of brake test on dc shunt motor including laboratory manual.
An eddy current load will be used as the load and the performance of the motor before and after load will be analyzed and studied. In cylindricaltype winding, the length of the coils is equal to the length of the core limb. Load test on singlephase transformer and three phase transformer connections. Thus, this method is an economical and convenient method of testing of dc machines. 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. Swinburnes test is the simplest indirect method of testing dc machines. Pdf on may 3, 2019, ahmed m t ibraheem alnaib and others published dc motors find, read and cite all the research you need on researchgate. Feb 24, 2018 thanks for a2a the no load loss in dc shunt motor can be also referred as constant loss of dc shunt motor actually it is the core loss that takes place inside the armature winding but the armature current is very very negligible in no load condi. The machine is running as a motor at rated voltage and speed. Dc shunt motor theory quiz questions electrician practice tests. In this post we had collected some of the most frequently asked electrical machines 1 viva questions with detailed answers.
In electrical terms, parallel is generally denoted as shunt. Brake test in one of the most simple way of finding efficiency of any kind of dc machine. The smaller the losses, the greater is the efficiency of the machine and viceversa. Because of their selfregulating speed capabilities, dc shunt motors are ideal for applications where precise speed control is required. Testing of dc motor, dc motor testing direct and indirect method. In this method, the dc machine generator or motor is run as a motor at no load and losses of the machine are determined.
The main advantages of the swinburnes test are as follows. Load test on singlephase transformer and three phase transformers. Electrical machines i lab auroras technological and. When we run a machine, then some energy is lost in the machine, which converts into the heat and cause temperature rise. S1 power switch to switch on sw1 speed switch and starter switch for armature sw2 speed switch for field winding r1 to r9 wirewound high power resistors for the starting of the motor sw2 must be on position 0. In other words, all of the electric power which is supplied to the motor is not. This parallel configuration allows independent path of current for field winding and armature. If the dc line voltage is constant, then the armature voltage and the field strength will be constant. In this experiment, a load test on dc shunt motor will be conducted. Motors electrical engineering multiple choice questions and answers. 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. Speed control of dc shunt motor with field and armature. The efficiency of a dc machine depends upon its losses.
Load test on dc shunt motor offered by unicon instruments, a leading supplier of dc shunt motor in sadar bazar, ambala, haryana. Retardation test or running down test on dc machines. Because loading will be applied directly on shaft of the motor by means of a belt and pulley arrangement. In this test the efficiency of the machine at any load is predetermined. The field current if and noload armature current iao are measured by suitable ammeters. Here we discuss about how to connect load test on d. It is an attempt to explain the experiment of load test on dc shunt motor in tamil by dr. Speed control of dc motor shunt type aim a to study the speed control of dc motor below the normal range by armature resistance control and to plot speed vs armature voltage, characteristic. Q what happens if dc supply is applied to the transformer. Dec 29, 2015 because of their selfregulating speed capabilities, dc shunt motors are ideal for applications where precise speed control is required.
The resistances of the armature and shunt field are 0. We can run the machine as a motor or as a generator. Electrical machines lab viva questions and answers. Dc shunt motor but field rheostat control method is most reliable, economic and independent of load on the motor. Brake test is also a method of finding efficiency of dc motors. Do search in wisdom jobs for dc motor job listings for full time and part time positions updated today. Let us address dc shunt motor, working principle, operational features, speed control, characteristics, load test, and applications of dc shunt motor respectively. Thus the load test on dc series motor was performed and the performance graphs were drawn. In this method, the dc machine is loaded directly by means of a brake applied to a water cooled pulley coupled to the shaft of the machine. To draw the performance characteristics of the given dc shunt motor by conducting load test. This test can be done in your own workshop using simple hand tools and a specialized electric testing. Selfexcitation in dc generator aim to observe voltage buildup in a selfexcited dc generator theory figure 1. Generally, this test can be done for the low rated dc machines.
Dc motor analysis a leader in electric motor testing. Load test on dc shunt motor unicon instruments exporter. That method is to change the terminal voltage of the motor. What you need is a variable dc power supply for this you need to know the ratings of the motor. This method is only applicable when we want speed which is higher than the normal speed of the motor. As said before, running some sorts of series motors off load will lead them to over speed and self destruct. If a shunt coil is added to a series motor at light loads when a series motor tends to overspeed the. Open circuit and short circuit tests on single phase transformer.
If the speed of this motor is reduced to 450 rpm by inserting a resistance in the armature. It is a type of motor that is used for constant load applications. It is supplied with one ms powder coated electrical panel fitted with high insulation bakelite sheet. The brake test is the one kind of load test on dc shunt motor. Jun 02, 2015 retardation or running down test this method is applicable to shunt motors and generators and is used for finding stray losses. Open circuit characteristic occ of dc shunt generator 2.
Mar 06, 2019 swinburnes test is the most commonly used and simplest method of testing of shunt and compound wound dc machines which have constant flux. In this experiment we aim to conduct a no load test on a dc generator to determine its open circuit characteristics followed by a load test on a dc shunt generator to determine its external load characteristics. This paper discusses the speed and torque control of a shunt dc motor through matlab simulink simulations. Speed control of dc shunt motor with field and armature rheostat control 79 2. Voltage buildup in selfexcited generator most of the shunt dc generators work on the principle of selfexcitation. Dc shunt motor shunt wound dc motor principle, construction. To obtain the performance characteristics of a dc shunt motor by load test. Dc motor is one of the rotary machines which makes use of electrical current and converts it to mechanical energy which can be used in many other functions or operations. That is the reason behind naming it a dc shunt motor. Swinburnes test and speed control of dc shunt motor. Brake test also called as direct loading test of testing the motor. As resistance increased, the value of the field current will reduce. In this method, the dc machine is loaded directly by means of a brake applied to.
The biggest advantage of swinburnes test is that the shunt machine is to be run as motor under no load condition requiring little power to be drawn from the supply based on the no load reading, efficiency can be predicted for any load current. 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. Once the losses of the machine are known, its efficiency at any desired load can be determined in advance. Same voltage is applied to both shunt winding and armature in this motor. So the load test could be performed in two ways ie, by direct loading by indirectly loading in case of direct loading the motor is provide. On the other hand, back emf reduces marginally more than that the. The dc generator as we know can be either separately excited or self excited in shunt. The company was incorporated in 1954 and is registered with indiamart. Depending on the motors design a tachometer system should be included. Open circuit and load characteristics of separately and self excited dc shunt generators. The load testing of dc machine is needed to determine the rating of a machine. This essentially means that on switching the motor running condition from no load to loaded, surprisingly there is no considerable change in speed of running, as would. Components of the shunt motor are the armature, labeled a1 and a 2, and the field, labeled f1 and f2.
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