The tendency of the rotor teeth to remain under the stator teeth due to direct magnetic attraction is reduced. Slip ring induction motor working principle electrical mastar. Record all nameplate information for the induction motor. Since here we are talking about maintenance of induction motor, and it is of two types. Operating characteristics of a woundrotor slipring. The rotor of an induction motor can be a squirrel cage rotor or wound. Some sections may explain explicitly between the three configurations, but have different requirements for each. They are especially suitable for heavy load inertia applications. Connect the resistor loading rack at the generator armature terminals. Draw the torque slip characteristics of 3 phase slip ring induction motor. Three phase induction motors electric motors bharat bijlee. Slip ring induction motor fundamentals pnpntransistor. The slip ring rotor chamber of the ic 411 slip ring induction motor is separated by what is known as a labyrinth seal, which prevents contamination from coal dust. Department of electrical engineering national institute of.
Blow dry air though the rotor and the stator in both directions, i. The test results with an induction motor load reveal that the proposed method is able. One benefit to doing so is that, if an eccentric air gap is suspected, the electrical noise will still be present. Show full abstract to determine the margin of stability and. The slip ring induction motor has two distinctly separate parts, one is the stator and other is the rotor. Squirrel cage motors have a rotor with short circuited bars whereas slipring motors have wound rotors having three windings each connected in star. On request, motors can also be constructed and tested according to other. Condition monitoring of slipring induction motor ijirae.
The construction of a stator is the same for both the squirrel cage and slip ring induction motor. Once the rotor reaches final speed, the rotor poles get switched to a short circuit, thus becoming electrically the same as a squirrel cage rotor. Home operating characteristics of a woundrotor slipring induction motor fig. Some changes in the stator may be encountered when a slip ring motor is used in a cascaded system, as the supply for the slave motor is controlled by the supply from the rotor of the other slip ring motor with external resistance mounted on its rotor. Control of motorcharacteristics by squirrelcage rotordesign. A woundrotor motor, also known as slip ringrotor motor, is a type of induction motor where the rotor windings are connected through slip rings to external resistance. According to the execution of brushes and sliprings the motors are classified into two. A low current supply mixedfrequency testrig has been proposed. Connection for load testing of a threephase induction motor. The oil ring lubrication process can be easily modified for flood lubrication. Mixedfrequency testing of induction machines using inverters.
Slip frequency is calculated by subtracting the actual operating speed of the motor from the synchronous speed. May 20, 2014 2 rocar arm field armature commutator carbon brush with holder slipring commutator centre fugal swit duration. Noload and blocked rotor test on an induction machine aim. C series motors but this disadvantages of the induction motor can be overcome by slip ring induction motor. Wound rotor induction motors ac motors electronics textbook. The stationary part of the induction motor windings stator connects to. With each load value, record the reading of v t, i a, w 1, w 2, v dc the speed n and i dc 10 amp scale in table 5. So the main idea behind motor maintenance is to prevent breakdown rather than repairs them. Slip ring motor conversion to vsd driven standard squirrel. Pdf design and analysis of drive system with slip ring. What happens if slip rings are short circuited in a 3 phase. Slip rings, also called rotary electrical interfaces, rotating electrical connectors, collectors, swivels, or electrical rotary joints, are commonly found in electric motors, electrical generators for ac systems.
In an induction motor, the electric current in the rotor needed to produce torque is obtained via electromagnetic induction from the rotating magnetic field of the stator winding. The mcemax performs tests on electric motors while the motor is running or when. Slipring collector tester a slip ring in electrical engineering terms is a method of making an electrical connection through a rotating assembly. The speed of an ac motor depends on the frequency of the input power and the number of poles for which the motor is wound. The rotor winding terminals are connected to three slip rings which turn with the rotor.
The induction motor stator resembles the stator of a revolving field, three phase alternator. Safe area motors motors for general application cga1d standard squirrel cage tefc motors. Induction motor testing and evaluation summary as energy costs rise, more emphasis is being placed on determining the health of large inductive motors. The static kramerdrive converts the slip power of an induction motor into ac power and supply back to the line. Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. The slip ring or wound rotor motor is an induction machine where the rotor comprises a set of coils that are terminated in sliprings to which external impedances can be connected.
Slip ring motors electrical calculations and induction. The slip power recovery scheme also plays a proactive role as there can be substantial savings of energy in case of a wound rotor induction motor as the slip power recovered can be used to drive. When the motor is started the total external resistance get added in the rotor winding resistance and the value of the resistances get gradually decreased with th. Slip ring induction motor working principle electrical. Slip is also expressed as a dimensionless ratio calculated as.
Testing of induction motor december 30, 2018 february 24, 2012 by electrical4u demand of energy is growing day by day and along with it cost of energy rising abruptly, so now it is necessary that the health of large motors which consumes maximum power should be taken care off. The slip ring rotor chamber has two modification openings. A wound rotor, has a 3phase winding similar to the stator winding. By far the most commonly used ac motor is the induction motor. If it was not caused by an operator tapping the button. Note locations relative to a reference point on the collector ring where runout is excessive. The induction motor is started by itself that we know. Each motor is given a routine test as required by bs4999, as59 or nema mg 1 to determine that it is.
Today, i am going to tell you about a wound rotor induction motor, which is also a type of 3 phase induction motor. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. Induction machines are considered relatively reliable and robust due to their simple design and welldeveloped manufacturing technology. Generally we all are know induction motor is most widely used motor in industrial. Depending on type of workload there are various type of starters for a slip ring induction motor. Diagnostics of rotor and stator problems in industrial induction motors by fang duan b. A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. This final thesis will mostly be dedicated to induction motors but also to synchronous permanent magnet and reluctance motors. The basic idea of an electric motor is to generate two magnetic fields. Lecture 6 three phase induction motors cairo university. It utilizes a low voltage, high frequency signal to measure the inductance l reading for each of the stator windings in a threephase ac induction motor.
Smooth starting of slip ring induction motors article pdf available in ieee transactions on energy conversion 124. Slip in electrical induction motors engineering toolbox. There are two types of induction motors, one with wound type rotor, also called slip ring motor and another one with squirrelcage rotor. Circuit diagram for noload and blockedrotor test on 3 phase induction motor a. Testing motors with motor circuit evaluation detecting rotor defects with mce testing technology is one of the newest forms of rotor testing in todays market. Higher is the inertia, higher has to be the accelerating torque, otherwise the start will be very long and the motor can be damaged by the heating. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. The squirrel cage induction motor is the most popular type of ac motor. What are the type of starter used for slip ring induction. Whats worse than a slip ring flashover on a critical wound rotor motor.
An optional test is to connect the stator leads together, and run the motor by energizing the rotor leads at the rated secondary voltage. O remove as much dust as possible with a vacuum cleaner. Gradually apply three phase voltage across motor stator terminals via the autotransformer d. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. The windings receive current through some kind of slipring arrangement. Diagnostics of rotor and stator problems in industrial. Note down the machine ratings and calculate rated current of the machine noload test.
Pdf rotor side control of high power slip ring induction motor. Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor. Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required. There are two types of induction motors, one with wound type rotor, also called slipring motor and another one with squirrelcage rotor. Testing facility iec has adopted testing procedure from csa, ieee 112method b i. The terminals of the rotor windings of the slipring motors. The slip ringsbrushes allow external resistors to be connected in series with the winding. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. Some sections may explain explicitly between the three configurations. Because of the large rotor resistance, this motor has a pullout torque occurring at a high slip, and its starting torque is quite high. Speed control of threephase slip ring induction motor by rotor resistance. I will tell about the construction of a wound rotor later in this article. In the induction motors used in lift and hoists, you will see a type of rotor called a slip ring rotor, whereas in most of the other applications you. What happens if slip rings are short circuited in a 3.
The main difference in a slip ring induction motor is on the rotor construction and usage. The stator or the stationary part consists of three phase winding held in place in the slots of a laminated. Percent slip is a way to measure the speed performance of an induction motor. Supplement acs800 igbt based slip power recovery system.
Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. The 3phase set of currents, each of equal magnitude and with a phase. Abstract condition monitoring of slipring induction motor have been a challenging task. This paper aims to represent routine test performing in three phase induction motor. A squirrelcage motor with this type of rotor construction is called nemadesign class d. Slip ring testing slipring collector tester a slip ring in electrical engineering terms is a method of making an electrical connection through a rotating assembly. The rotor will constantly be turning to align its magnetic field with that of the stator field.
Telecommunication engineering, southwest jiaotong university, china, 2005 thesis submitted for the degree of masters of engineering science in school of electrical and electronic engineering the university of adelaide, australia august 2010. Motor current monitoring and analysis mcsa is a straight forward tool to diagnosing problems with large inductive motors. But the rotor construction differs with respect to the type of motor. Adjusting the resistance allows control of the speedtorque characteristic of the motor. First noload test the noload test, like the open circuit test on a transformer, gives information about exciting current and rotational losses. When the 3 phase supply is provided to the stator, a magnetic field is produced which rotates the rotor and motor starts. Induction motor parameters locked rotor test the locked rotor. To study and measure direct and quadrature axis reactance.
Slip ring motor fundamentals bright hub engineering. Slipring induction motor connection and testing youtube. Three phase slip ring induction motor my tech info. Over a number of years slip ring motors have largely been replaced by standard squirrel cage ac induction motors, often in conjunction with ac variable speed drives vsds. In order to start a slip ring motor, the accelerating torque has to be sufficiently higher than the resisting torque. Testing of a squirrel cage rotor requires some understanding of how the rotor functions. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load.
A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv. Squirrel cage induction motors a stator construction. Selecting the correct squirrel cage motor to replace a slip ring motor has been challenging for those doing the selection. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below. In addition to conventional squirrel cage rotor testing methods such as the growler test, also covered will be techniques such as the use of a core loss tester, high current excitation, and spectrum analysis of vibration. The rotor of an induction motor is like the secondary winding of a transformer, with the motor stator being the primary. The slip ring motor has very little application in industries.
The rotor of the slip ring induction motor is connected to the external resistances. Dec 30, 2018 testing of induction motor december 30, 2018 february 24, 2012 by electrical4u demand of energy is growing day by day and along with it cost of energy rising abruptly, so now it is necessary that the health of large motors which consumes maximum power should be taken care off. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals. Slip ring induction motor application slip ring induction motor provides high starting torque. You should also make a dc measurement of stator winding linetoline resistance using a dmm. For load sharing to take place automatically, the motor speed should drop considerably as the load increases and this is ensured by using a motor having a high fullload slip, say for example 10%. The test is performed by applying balanced rated voltage on the stator.
But at the starting of the induction motor, starting current is very large which may damage motor windings. The rotor of the slip ring induction motor is also cylindrical or constructed of lamination. The construction of stator of the induction motor is almost the same as other motors. If the slip ring induction motor is started with all the slip rings or the rotor terminals.
So, this motor is used in applications like lifts, pumps, mills where we require high starting torque. Slipring induction motor connection and testing people education online. Generally, induction motor provides low starting torque as compared to d. In this test, the alternator is run with the prime mover i. The slip power is the air gap power between the stator and the rotor of an induction motor which is not converted into mechanical power. If it was not caused by an operator tapping the button, it could be a weak magnetic holding coil allowing. This is easiest to visualize at motor startup, when the rotor is not yet turning. All motors comply with the following indian and international standards.
You can find manuals and other product documents in pdf format on the internet. Wound rotor induction motor the engineering projects. If the external controller is set at zero resistance, the motor operates almost exactly the same as the squirrelcage motor, since the rotor is shortcircuited. Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. Also record the manufacturers acceptable collector ring runout. Induction motor is one of the most important motor used in industrial applications. Motor runs smoothly as the magnetic hum is reduced b.
It is well known that induction motor testing standards vary significantly in their defined methodologies, instrumentation accuracy, and testing procedures. And determine the full load regulation of a three phase synchronous generator by synchronous impedance method 3. The stator of slip ring induction motor is very much the same as that of the squirrel cage induction motor, but the construction of its rotor is very much different. This is easiest to visualize at motor startup, when the rotor. It can improve mechanical performance, simplify system operation and eliminate damageprone wires dangling from movable joints. Squirrel cage induction motor requires significantly less maintenance as it does not contain brushes, commutators, slip rings. Disconnect any mechanical load connected to the induction motor. Each motor is given a routine test as required by bs4999, as59 or nema mg 1.
Starters limit the starting current in an induction motor which goes 56 times of full load current as slip remains 1. Slipring induction motor also known as rotor resistance start motor. When inspecting a wound rotor motor and the rotor lead is the point of failure, the transient caused by a rapid restrike is a strong contender for the root cause of the failure. The rotor terminals are connected to three slip rings which turn with the. Examine the slip ring helical groove edge chamfering. Number of poles, frequencies and synchronous induction motor speed. Starting of slip ring induction motor explained in an easy. Explain starting methods of 3 phase induction motor. For a motor with slip rings, measure and record the collector ring wear and concentricity. The stator is the same as is used with a standard squirrel cage motor. The motor is mounted in a test rig that allows one to control the torque applied to the motor shaft and to measure both rpm and torque. Rotating electrical machinery natural graphite brush for slipring in wound rotortype induction motor application information.
Dec 01, 2017 slipring induction motor also known as rotor resistance start motor. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. The ld language enables the description of tests and modifications of. Testing 100% routine test quality is emphasised at each step as a motor proceeds through each stage of design, assembly and testing. Learn more about the construction and operation of a slip ring induction motor. The load test on induction motor is performed to compute its complete performance i. When a motor starts to rotate the slip is 100 % and the motor current is at maximum. Stator winding can be either star or delta connected depending upon the design.