By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. There is no difference between squirrel cage and slip ring motors. They are also referred to as the short circuit test and open circuit test respectively in. Percent slip is a way to measure the speed performance of an induction motor. 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. No load test and locked rotor test in an induction motor. 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. This manual covers squirrel cage rotor motor where the rotor consists of a set of noninsulated bars that are interconnected by shortcircuiting rings. What is the working principle of slip ring induction motor. Pdf rotor side control of high power slip ring induction motor. Such motors combine a low starting current with a low starting torque and may.
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%. When a motor starts to rotate the slip is 100 % and the motor current is at maximum. The main difference in a slip ring induction motor is on the rotor construction and usage. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. Stator winding can be either star or delta connected depending upon the design. The additional machine helps to supply the friction and windage losses, under this conditions, the slip s0 and the current drawn by the induction motor is i o only since s0, the term r l r 2 1s1 becomes the load resistance r l 0.
A squirrel cage induction motor takes 600 % to 700% of the full load current, but a slip ring induction motor takes a very low starting current approximately 250 % to 350% of the full load current. The squirrel cage induction motor is the most popular type of ac motor. The stator is the same as is used with a standard squirrel cage motor. Slipring induction motor also known as rotor resistance start motor. They are especially suitable for heavy load inertia applications. This magnetic field opposes the revolving magnetic field and will combine with the.
The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. Load test on three phase slip ring induction motor in. Y provides smooth and stepless cutting of resistance in rotor circuit of the motor, reducing starting current and. To find out g o and b o the induction motor is made to run at synchronous speed by using another machine. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. Slip ring induction motor working principle electrical. Dynamic analysis of cage rotor induction motor using harmonic. Record the specifications of the induction motor im arrange and measure the resistance of the load rack in the same manner as in the previous experiment for 6 different readings. C series motors but this disadvantages of the induction motor can be overcome by slip ring induction motor.
Ysalient features y robust and nonflammable construction. Rotors of induction motors are of two types, the squirrel cage and the wound. In three phase induction motor, the power is transferred from stator to. Figure shows the disassembled view of an induction motor with squirrel cage rotor. A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. Generally, induction motor provides low starting torque as compared to d.
However, motors suitable for foot flange face mounting or any combination of these with vertical or horizontal orientation can be offered when required. Construction of three phase induction motor electrical4u. Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required. Theory of no load test of induction motor the impedance of magnetizing path of induction motor is large enough to obstruct flow of current. And determine the full load regulation of a three phase synchronous generator by synchronous impedance method 3. In order to start a slip ring motor, the accelerating torque has to be sufficiently higher than the resisting torque. To conduct the load test on 3phase induction motor.
The torque produced by the induction motor is directly proportional to induction motor slip. The magnetic winding is made by joining coils to form phases. Short out the slip rings and the motor will run just like a standard induction motor. What external resistance per phase must be added in the rotor circuit so that the motor now runs ate a slip of 17.
The construction of a stator is the same for both the squirrel cage and slip ring induction motor. A typical squirrel cage, three phase induction motor is shown in figure 1. Slip in electrical induction motors engineering toolbox. The slip ring rotor chamber has two modification openings. Also find the current and power factor under this condition. A slip ring is also used in applications where the load require good. Matlabsimulink based design and simulation of speed. Users occasionally inquire as to the feasibility of converting an existing woundrotor moto. If the motor slip is known, the rotor speed can be expressed by the equation. How to convert a slip ring motor into squirrel cage motor.
Slip ring motor fundamentals bright hub engineering. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. Compared to squirrel cage rotor the rotor construction is not simple. Krause 26 proposed a more comprehensive reference frame to combine different. Form noload test i 0 is known and f 0 is found out as taking all quantities on per phase values. Generally we all are know induction motor is most widely used motor in industrial. Torque slip characteristics of induction motor electrical4u. Selecting an oversized ac induction motor also reduces slip. First noload test the noload test, like the open circuit test on a transformer, gives information about exciting current and rotational losses. To draw circle diagram for a three phase induction motor. With the advent of variablefrequency solidstate power supplies, speed variation can be provided by the more reliable, less expensive squirrelcage motor.
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. Effects of rotor asymmetry conference paper pdf available june 1997 with 3,082 reads how we measure reads. Depending on type of workload there are various type of starters for a slip ring induction motor. The load test on induction motor is performed to compute its complete performance i. In squirrel cage induction motors the rotor is simplest and most rugged in construction.
Figure 16 perphase equivalent circuit under no load test condition. The basic idea of an electric motor is to generate two magnetic fields. The slip ring induction motor has two distinctly separate parts, one is the stator and other is the rotor. Slip ring motors are normally available with foot mounting flange mounting can be supplied on specific request. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals. Slip ring induction motor fundamentals pnpntransistor. Load test on three phase slip ring induction motor in tamil deeeiv sememip. The slip rings shall be shortcircuited for this test. An induction motor or asynchronous motor is an ac electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motors rotor can be either wound type or squirrelcage type. The following tests are performed on an alternator to know itsb performance. Initially, the name plate details of three phase slip ring induction motor whose speed is to be controlled is noted and by conducting noload test and locked rotor test on the motor the equivalent electrical. Starters limit the starting current in an induction motor which goes 56 times of full load current as slip remains 1.
Setup of load characteristics of 3 phase slip ring. Motors and drives ac induction motor slip what it is and. The construction of the slip ring induction motor is exactly similar to the. In slip ring induction motors the rotor is wound type. During this test, the motor is operated at rated voltage and frequency and normally loaded mechanically by brake and pulley arrangement. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. The rotor resistance per phase of the winding is 0. It can improve mechanical performance, simplify system operation and eliminate damageprone wires dangling from movable joints. No load test of an induction motor no load test is an indirect method used for determining the efficiency and also to determine the circuit parameters of the equivalent circuit of the threephase induction motors. The test is performed by applying balanced rated voltage on the stator.
Slip ring motors electrical calculations and induction. The required power is 10 hp at about 1,800 rpm and 1. The speed of rotor, nr droops slightly as the load on the motor is increased. The slip is defined as the ratio of difference of synchronous speed and actual rotor. Slipring induction motor connection and testing youtube. The circuit diagram of load test on 3 phase squirrel cage induction motor. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv. This magnetic field opposes the revolving magnetic field and will combine with.
What are the type of starter used for slip ring induction. Therefore, small current is applied to the machine due to which there is a fall in the statorimpedance value and rated voltage is applied across the magnetizing branch. No load test is same as the open circuit test performed on the transformer. Starting of slip ring induction motor explained in an easy. A load test may be applied to an induction motor to determine its performance at. In a noload test, an induction motor took 10 a and 450 watts with a line voltage. An 8 pole, 50 hz slip ring induction motor runs at a slip of 2.
Almost 80% of the mechanical power used by industries is provided by three phase induction motors because of its simple and rugged construction, low cost, good operating characteristics, the absence of commutator and good speed regulation. It is expressed by the percentage of synchronous speed. Torque slip characteristics of three phase induction motor. Slip of induction motor plays an important role in the operation of the induction motor. Number of poles, frequencies and synchronous induction motor speed.
Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. 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. To study and measure direct and quadrature axis reactance. The open circuit test performed on the transformer. The rotor will constantly be turning to align its magnetic field with that of the stator field. The three phase induction motor is the most widely used electrical motor. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load. Squirrel cage induction motor vs slip ring induction motor. Ieee std 1122004, ieee standard test procedure for polyphase. Crane duty motors, slip ring crane duty motors, squirrel. Simulations has been performed using the ideal constant mathematical model of three phase induction. Normally, the range of slip at full load is from 2 to 5 percent. The 3phase set of currents, each of equal magnitude and with a phase.
The slip ring motor has very little application in industries. A squirrelcage rotor is designed with a fixed shaft containing a laminated iron core. These three increased losses combine to increase the in put for a given. The stray load loss is determined by combining the above fundamental frequency and the highfrequency. The examination of dtcsvm induction motor drive dynamic in case of rapid changes of load torque, as well as in terms of shortlived supply voltage distortions was a purpose of this study. Show full abstract to determine the margin of stability and.
Three phase slip ring induction motor my tech info. Chapter 3 induction motor and different speed control methods page no 3. To construct the circle diagram three tests are to be performed, namely a noload test. A 3phase star connected, 440v, 4pole, 50hz, slip ring induction motor gave. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. The value of slip in induction motor at full load varies from about 6% for small motors to about 2% for large motors. The slip in an induction motor is the difference between the main flux speed and their rotor speed. Wound rotor with slip rings the rotating magnetic field. The value of slip at full load varies from 6% in case of small motor and 2% in the large motor. This motor is much heavier than the 22kw slip ring motor and resistor bank so the crane had to be rerated as well. Squirrel cage crane duty motors are supplied with horizontal foot mounting. Starting torque of slip ring motor and induction motor. In this test, a rated, balanced ac voltage at a rated frequency is applied to the stator while it is running at no load. Learn more about the construction and operation of a slip ring induction motor.
Larger motors exhibit less slip, and it gets smaller with a partial rather than full motor load. The test results with an induction motor load reveal that the proposed method is able. Slip ring motors are normally used where additional torque is required to overcome the inertia of the. An induction motor can therefore be made without electrical connections to the rotor. Mechanical loading is the most common type of method employed in laboratories, a brake drum is coupled to the shaft of the motor and the load is applied by tightening the belt, provided on the brake drum. Therefore, it is customary to combine them in to a single reactance.