If you happen to have a string of blinking christmas lights to use as a prop in illustrating a rotating magnetic field, this would be a good thing to show your students. Jun 02, 2015 brake test it is a direct method and consists of applying a brake to a watercooled pulley mounted on the motor shaft as shown in fig. Electrical machinel dc laboratory manual grietelectrical and. Construction and principle of operation of the shunt dc motor. Introduction a series dc motor is a motor whose filed windings consists of a relatively few turns connected in. Dc motors dc motor theory dc motor theory dc motors are widely used to drive various equipment. To obtain the performance characteristics of a dc shunt motor by load test. The extra terminal draws about 4 amps when connected high. This is the ninth lesson in the acdc motor theory course. In a brushed dc motor, the coils on the rotor utilize the motors magnetic eld to create torque on the axle.
Armature reaction, compensation, and induced voltage. That is the reason behind naming it a dc shunt motor. Fields test for series motor this test is applicable to two similar series. Module 2 basic dc theory this module describes the basic concepts of direct current dc electrical circuits and discusses the associated terminology. Dc drive is basically a dc motor speed control system that supplies the voltage to the motor to operate at desired speed. In a compound motor, we have both series winding and parallel winding.
The dc compound motor consists of both series and shunt field windings. Dec 21, 2017 81 videos play all dc machines complete course includes fundamentals, motors and generators electrical is easy mix play all mix electrical is easy youtube troubleshooting a motor starter. The development of the electric motor in modern times has indicated the truth in this theory. As im only running motor unloaded on 12 voltage, any regulating effect may not be noticed. Compound wound dc motors basic drive circuits drive circuits are used in applications where a controller of some kind is being used and speed control is required. A compoundwound motor has both a series and a shunt field winding, i. Earlier, the variable dc voltage for the speed control of an industrial dc motor was generated by a dc generator. Two basic methods used for braking a motor dc injection and dynamic photo credit.
Dec 19, 2016 we connect the compound dc motor with the series and shunt windings with opposite polarities giving us a differential connection and lots of flames coming out of the brushes while running. Explain how this motor can be operated as either a synchronous motor or a plain induction motor. An ac motor works by applying alternating current to stator windings, which produce a rotating magnetic field. Brake test of dc motor is carried out as shown in figure below. Apr 25, 2018 dc machines can be tested by three different methods namely direct method, indirect method and regenerative method. Brushed dc motor fundamentals microchip technology. N s this particular motor is of the permanent magnet type, with wire windings only on the armature. A dc motor may be thought of as a series of electromagnets, radially spaced around a common shaft. The induction motor is made up of the stator, or stationary windings, and the rotor. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. The armature and its windings are located in the path of this magnetic field, and. Brake test it is a direct method and consists of applying a brake to a watercooled pulley mounted on the motor shaft as shown in fig. The speed and torque produced in a dc motor depends on a variety of factors.
The cumulative compound wound dc motor is well adapted for this type of work. A compound wound dc motor also known as a dc compound motor is a type of selfexcited motor, and is made up of both series the field coils s 1 s 2 and shunt field coils f 1 f 2 connected to the armature winding as shown in the figure below. In this method, a brake is applied to a watercooled pulley mounted on the motor shaft as shown in fig. Overview the acdc motor theory course was specifically developed for electricians and electronic technicians as well as for the multicraft training needs of process and manufacturing facilities. Write the necessary magnetic polarities n for north and s for south on the armatures. We connect the compound dc motor with the series and shunt windings with opposite polarities giving us a differential connection and lots of flames coming out of the brushes while running. Because the magnetic field rotates in this way, an ac motor does not need.
The eighth lesson in the acdc motor theory course, this lesson demonstrates armature reaction, compensation, and induced voltage. Brake test on dc shunt motor free download as word doc. Its operation is based on the principle that when a current carrying conductor is placed in a. There are 3 main types of dc motor that are available. Differential compound dc motor connections youtube. The open circuit test gives the mmf and hence the excitation current or field current needed to generate the required voltage on no load at a fixed speed. When the losses of dc machine wellknown, then we can find the efficiency of a dc machine in advance at any desired load. Experiment 7 series dc motor i objectives to determine the torquespeed characteristic curve. Both the field coils provide for the required amount of magnetic flux, that links with the armature.
Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. Nov 02, 2015 load test on dc compound generator long shunt 1. Volume 2 of 4 module 3 dc circuits this module introduces the rules associated with the reactive components of inductance and capacitance and how they affect dc circuits. Another simple method of measuring motor output is by the use of poney brake one form of which is shown in fig. The concept of the rotating magnetic field is central to ac motor theory, so it is imperative that students grasp this concept before moving on to more advanced concepts. One end of the rope is fixed to the floor via a spring balance s and a known mass is suspended at the other end. Electrodynamometer is an electrical break, in which the breaking force can be varied electrically. Objective identify the components of an ac motor and explain their function. The open circuit characteristics for a dc generator are determined as follows. Same voltage is applied to both shunt winding and armature in this motor. Because the magnetic field rotates in this way, an ac motor does not need power or mechanical aid to be applied to the rotor. Suitable for use with intermittent loads such as lifts, hoists etc.
This parallel configuration allows independent path of current for field winding and armature. This course consists of 11 interactive, online lessons that address ac and dc motor theory. One end of the band is fixed to earth via a spring balance s. In a brushed dc motor, the coils on the rotor utilize the motors magnetic eld. In electrical terms, parallel is generally denoted as shunt. Using belt tightening hand wheels h1 and h2, the load of motor is adjusted to its rated value. Dc motor dc motor theory the dc motor has two basic parts. Direct method of testing of dc machine, also known as brake test if carried out for a dc motor will be discussed in this post. To find out how to reverse the direction of rotation of a series dc motor.
Mar 23, 2019 a compound wound dc motor also known as a dc compound motor is a type of selfexcited motor, and is made up of both series the field coils s 1 s 2 and shunt field coils f 1 f 2 connected to the armature winding as shown in the figure below. Dc series motor theory quiz questions electrician practice. Because loading will be applied directly on shaft of the motor by means of a belt and pulley arrangement. Brake test is also a method of finding efficiency of dc motors. Motor runs about the same with it connected high or low.
Characteristics of compound motor 34 compound motor characteristics are intermediate between the shunt and series motors torquespeed of compound motor shows that the motor has high starting torque together with a safe noload speed. Basic motor theory introduction it has been said that if the ancient romans, 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. Like any other motor, series motors convert electrical energy to mechanical energy. A compound wound motor has both a series and a shunt field winding, i.
Each type has unique operating characteristics and applications. The brake band is fixed with the help of wooden blocks gripping the pulley. A good material for the poles of a pmdc motor should have the apposite of the above. A dc generator requires an excitation circuit to generate an induce voltage depending on whether excitation. The open circuit test is needed to determine the open circuit characteristic or magnetizing characteristic of a dc machine.
Make sure that no load is applied on the motors and the motor field rheostat should be in minimum position. My motor is a series motor with only one terminal available. Dec 30, 2018 the open circuit test is needed to determine the open circuit characteristic or magnetizing characteristic of a dc machine. Dc injection braking is a method of braking in which direct current dc is applied to the stationary windings of an ac motor after the ac voltage is removed. This lesson instructs the participant in the design of series. Introduction a series dc motor is a motor whose filed windings consists of a relatively few turns connected in series with the armature circuit. The dc motor contains a stator and a rotor, the latter being more commonly called an armature. In case of dc shunt motors, armature is disconnected from the supply and a rheostat variable resistor is connected across it. A belt around the air cooled pulley has its end attached to the spring balance s1 and s2. Brake test on dc compound motor free download as word doc. Electrical machines laboratory roever college of engineering and. In this article we are going to discuss about brake test on d. Its operation is based on simple electromagnetic principle by which when the magnetic field created around a current carrying conductor interacts with an external magnetic field, a rotational motion is generated.
The simple brake test described above can be used for small motors only, because in the case of large motors, it is difficult to dissipate the large amount of heat generated at the brake. Dc motor theory mem 639 realtime microcomputer control 1. And series field coil is exposed to the entire supply current, before being split up into armature and shunt field current as shown in the diagram below. Describe how a squirrel cage motor is built, and classify it as either an induction motor or a synchronous motor.
Dc compound motor or compound wound dc motor is also a selfexcited motor, but it is a compound of both series and shunt field coils connected to the armature winding, a series field winding connected in series with the armature and a shunt field winding connected in parallel to the armature. Swinburnes test for dc machines in this technique, the dc generator or dc motor is run as a motor at no load. The armature is made of coils of wire wrapped around the core, and the core has an extended shaft that rotates on bearings. A winding is connected in series with the armature as in a series dc motor. Dc machines can be tested by three different methods namely direct method, indirect method and regenerative method. Brake test also called as direct loading test of testing the motor. The electric braking of a dc motor is of three types, i rheostatic or dynamic braking, ii plugging or reverse current braking and iii regenerative beaking. Download as docx, pdf, txt or read online from scribd. A dc series motor will have its field windings connected in series with the armature. These terms relate to the type of connection of the field windings with respect to the armature circuit. Compound wound dc motor or dc compound motor electrical4u. Brushed dc motor theory and operation chris joyce, shane skikne, evan simpson, james nee january 8, 2014 abstract this study looked into the e ect of changing the material within the rotor of an electric motor. Dc compound motor is essentially a combination of series dc motor and shunt dc motor. Start the motor by using 3point starter and adjust the speed of the motor in the rated value by using rheostat of motor 4.
Dc compound motor definition, types, applications, equations. Write the necessary magnetic polarities n for north and s for south on the armatures electromagnet pole tips, in order to. The field current lf is obtained from an external independent dc source. Compound motor series and shunt windings in the same machine combine to make the field flux. Brake test on dc compound motor electric motor electrical. Brake test on dc shunt motor electric motor electrical. In long shunt dc compound motor, the shunt field winding is connected across both armature and series field winding. Dc motors although ac motors are used in most of the cases, dc motors have many applications and used for multipurpose applications. The stator contains one or more windings per pole, all of which are designed to carry direct current, th ereby setting up a magnetic field. Dc series motor theory quiz questions free online electrical practice tests.
1491 568 973 1016 795 829 541 941 668 240 1038 360 1614 605 482 1364 1526 1446 1391 1376 924 1265 364 1106 398 420 653 887 470 844 861 88 621