Pdf speed control of squirrel cage induction motor sqim. The stator separate from rotor by small air gap have ranges from 0. Instead of a series of rotor bars, a set of insulated rotor coils is. Speed control of wound rotor induction motor using rotor resistance control aim. Pdf dynamic simulation of starting and chopper speed control of. The stator of the motor is assumed to be supplied by threephase voltages with frequency and magnitude that may vary. The rotor windings are usually of a threephase type with three connections made to insulated conducting rings known as slip rings mounted on an internal part of the rotor. Speed regulation of induction motors with wound rotor. The traditional way to control the speed of a wound rotor induction motor is to increase the slip by adding resistance in the rotor circuit. In this scheme, the number of pole pairs is changed by changing the field connection. The technique of starting wound rotor motors with resistance in the rotor circuit is also used for speed control applications. Jan 05, 2016 speed control we have seen that to operate eyciently an induction motor must run with a small slip.
Wound rotor motors deliver speed control of heavy and hightorque loads. The slip ring in duction motor has a number of disadvantages compared to squirrel cage motor such as 1. Let us call this procedure additional voltage to the rotor. The torque developed in this method is proportional to the square of the supply voltage. This speed control technique is only useful over a range of 50% to 100% of full speed. In induction motor, field winding is wound on the stator while the armature winding is wound on the rotor. Not only can we slow the rotor by 50 %, but we can also over speed it by 50 %. When the rotor of ims is provided with a wound rotor, speed control is performed by adding a variable resistor to the rotor circuit connecting a power converter to the rotor to introduce or extract power from the rotor. Starting andcontrol of slipring 5 electrical engineering book. Additional series resistance reduces voltage across main windings. Threephase squirrelcage induction motors are widely used in industrial drives because they are rugged, reliable and economical. Since the slip of an induction motor increases as the rotor resistance increases, some speed control is possible using a wound rotor motor and varying the rotor resistance while running. Three phase supply is given to the primary with the help. Generally, induction motor provides low starting torque as compared to d.
Wound rotor induction motor, speed control, torque control, pi controller. This paper sets forth a technique to operate wound rotor induction motor in maximum torque region, using a feedback mechanism using rotor speed and slip. Speed control of induction motor 7 ways to control. You should also make a dc measurement of stator winding linetoline resistance using a dmm. The induction motor is made up of the stator, or stationary windings, and the rotor. In contrast, a traditional induction motor aka squirrel cage motor has windings that are permanently shortcircuited by an end ring. A motor does not naturally maintain a constant speed as the torque varies. The motivation lies in the possible use of such motors for hybrid electric propulsion. Jan 09, 2017 this method is applicable to squirrel cage induction motor only. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting.
This starter is used with a wound rotor induction motor. In previous articles i have discussed the construction, operation, starting, speed control, and classes of squirrel cage induction motors. An induction motor is practically a constant speed motor, that means, for the entire loading range, change in speed of the motor is quite small. In wound rotor induction motor, the rotor has a 3 phase winding similar to stator winding.
Speed control of single phase ac induction motor possible. Speed control of induction motor detailed explanation. Initial start up testing of 1915 vintage 750 hp wound. Consider the equivalent circuit of a wound rotor induction machine with the rotor circuit not referred to the stator. Speed control for doublyfed induction motors with and. Performance enhancement of wound rotor induction motor by vsi. A 3 phase induction motor can be used for different applications with various speed and load requirements. But the recent developments in speed control methods of the asynchronous motor have led.
The speed torque curves of the wound rotor induction motor, 289. Asynchronous motors are the most widely used electrical motors due to their reliability, low cost, ruggedness and robustness. Pole changing method speed control of induction motor. The rotor will constantly be turning to align its magnetic field with that of the stator field.
Variation of the rotor resistance is studied as the means of changing the rotor speed of wound rotor induction machines. Adjusting the resistance allows control of the speed torque characteristic of the motor. When the speed control of three phase induction motor is done by adding resistance in rotor circuit, some part of power called, the slip power is lost as i 2 r losses. The regulation of speed is required in many applications of induction motors, including in electric locomotives and electric driving vehicles. To use variable resistance in the rotor circuit to control wound rotor induction motor speed theory polyphase induction motors are mainly of two types by construction, squirrel cage and wound rotor with sliprings. An induction motor s rotor can be either wound type or squirrelcage type.
The 3phase set of currents, each of equal magnitude and with a phase. Induction motor general principle electromagnetism. Wound rotor tecowestinghouse motor company, a world leader. Since the speed of a wound rotor induction motor may be controlled over a range of 50100 % by inserting resistance in the rotor, we may expect the same of the doublyfed induction generator. A slip ring is also used in applications where the load require good speed control. Speed control of 3 phase induction motor a 3 phase induction motor is practically constant speed motor provided that applied parameters supply, frequency etc. Schrage motor can be treated as an inverted poly phase induction motor. The speed regulation is poor with respect to changing torque loads. With a liquid rheostat, or a static secondary speed control, the wound rotor is an important alternative drive where limited range adjustable speed is required.
Speed control of three phase induction motor electrical4u. Induction motor generator mode induction motor maximum torque using thevenin equivalent thevenin equivalent voltage of. It uses an external resistancephase in the rotor circuit so that rotor will develop a high value of torque. With a highinertia load a standard cage induction motor may suffer rotor damage on starting due to the power dissipated by the rotor. Aug 25, 2018 schrage motor is essentially a combination of wound rotor induction motor and frequency convertor. This type of 3phase induction motor has high starting torque, which makes it ideal for applications where standard nema design motors fall short. The problem with the capacitive reactance control is the demand of high capacitance requirement and high torque ripples during motor operation. Speed control of 3phase induction motor using pic18 microcontrollers. High torque is produced at low speeds, when the external resistance is at its higher value.
Wound rotor tecowestinghouse motor company, a world. 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. The speed is controlled by changing the external resistance in the rotor circuit. A woundrotor motor is a type of induction motor where the rotor windings are connected through slip rings to external resistance. Speed control methods for a 3 phase induction motor. The speed of induction motor can be varied by changing supply voltage.
In recent advancements in electric machine and drives, wound rotor motor is extensively used. Speed control of induction motor speed control of induction motor by vf method speed control of three phase induction motor with universal controller 3 phase induction motor pdf three phase induction motor the wound rotor induction motor three phase induction motor diagram induction motor problems and solutions pdf blocked circle diagram of an induction motor single phase induction motor pdf. In this paper the speed control problem for a wound rotor induction motor is considered. Power supply, dai, wound rotor induction motor 8231, electrodynamometer 8960, timing belt.
Rotor resistance control in wound rotor induction motor, it is possible to change the shape of the torque speed curve by inserting extra resistance into rotor circuit of the machine. Apr 06, 2017 when the rotor of ims is provided with a wound rotor, speed control is performed by adding a variable resistor to the rotor circuit connecting a power converter to the rotor to introduce or extract power from the rotor. The resulting torque speed characteristic curves are shown in fig. Starting and control of slipring induction motors597 the use of wound motors is on the wane, for reasons of inherent advantages of a squirrel cage motor over a wound. In the proposed control, dynamic capacitor is used for. The merit of using wound rotor induction motor is to control speed torque characteristics by inserting external resistance. Introduction threephase woundrotor induction machines 1. Wound rotor induction motor wrim speed torque curves, 2. What makes the wound rotor motor a unique induction machine is its rotor. Connecting a power converter to the rotor to introduce or extract power from the rotor.
For an induction motor with p polesand f frequency, slip for induction motors a very important parameter is the slip of the motor the slip, s, defines the relative speed difference between synchronous speed and rotor speed and is given by. Various induction motor speed control methods advantages. Woundrotor motors deliver speed control of heavy and hightorque loads. Speed control works well with variable speed loads like elevators and printing presses. Rotor resistance controls the speed of wound rotor induction motor. Rotor side control of gridconnected wound rotor induction machine. This not only gives reliable starting but also ensures the best protection for your investment. Rotor is also cylindrical in shape and has slots to carry winding.
Sep 28, 2016 the speed torque curves of the wound rotor induction motor, 2892016 lutfi alsharif. Sometimes theyre talking about induction motors, other times not, and they dont specify which is which, or even which induction motor type they are talking about. This method is applicable to squirrel cage induction motor only. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. The speed of a threephase induction motor driving a given load is determined by matching the torque speed characteristics of the motor and load, as shown in fig. Record all nameplate information for the induction motor. Instead of a series of rotor bars, a set of insulated rotor coils is used to accept external impedances.
Starting and control of slipring induction motors597 the use of wound motors is on the wane, for reasons of inherent advantages of a squirrel cage motor over a wound motor and the availability of static drives which can make a squirrel cage motor perform the same duties as a wound motor and even better. Wound rotor induction motors some special induction motors are constructed with insulated coils in the rotor similar to those in the stator winding. As induction motors are widely being used, their speed control may be required in many applications. The rotor is supplied by a bidirectional converter. The speed of induction motor depends on various factors, like supplied voltage, frequency, number of poles. Performance enhancement of wound rotor induction motor by. Woundrotor motor, starting, speed control, dynamic simulation, cartesian coordinates. I will tell you about the construction of wound rotor induction motor in the first section. A wound rotor induction motor is also known as slip ring induction motor. Therefore the efficiency of three phase induction motor is reduced by this method of speed control. Ac induction motor speed control so what can we do to control the speed of an ac induction motor. We can change the speed at the stator by, changing the supply frequency, changing the supply voltage and changing the number of stator poles. It is hard to learn anything valueable from that page.
Wound rotor induction motors ac motors electronics. Constant speed drive control for a wound rotor induction. Pdf in this study, the speed and torque of a wound rotor induction motor wrim have been controlled by. Schrage motor operation principle and characteristics of. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. Speed control of induction motor is possible in two sides. A wound rotor induction motor has a stator like a squirrel cage induction. With a liquid rheostat, or a static secondary speed control, the wound rotor is an important alternative drive where limited range adjustable speed. This article will highlight the important concepts for wound rotor motors that must be understood before purchasing one of these but know it is not allinclusive.
Woundrotor motors can be started with low inrush current, by inserting high resistance into. Historically, it has been used for hardtostart, high inertia fans, or where power system requirements demand a soft start. Threephase squirrelcage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. Unlike induction motor the primary winding of schrage motor is on the rotor. Slip control is only possible with wound rotor induction motors. Jul 17, 2017 the stator of a wound rotor motor is the same as a typical induction motor, but the rotor has a threephase winding, with each of the winding terminals connected to separate slip rings. Wound rotor induction motors ac motors electronics textbook. Pdf torque and speed control of wound rotor induction motor by. Polyphase induction motors are mainly of two types by construction, squirrel cage and woundrotorwith sliprings. Maintenance and reliability problems due to brushes and slip rin gs however, a wound rotor srim. Due to this reason, earlier dc motors were applied in most of the electrical drives. The wound rotor induction motor has some distinct application advantages. The basic idea of an electric motor is to generate two magnetic fields.
A wound rotor motor, also known as slip ring rotor motor, is a type of induction motor where the rotor windings are connected through slip rings to external resistance. By eliminating the need for a rotor mounted synchronizing module, ge has further improved motor reliability. Speed of a dc shunt motor can be varied very easily with good efficiency, but in case of induction motors, speed reduction is accompanied by a corresponding loss of efficiency and poor power factor. A wound rotor induction motor has a stator like the squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. Controllers for wound rotor motors include for the stator the same protection and switching functions that are used for squirrel cage motors. Induction motors mainly consists of two types rotors which are wound rotor and squirrel cage rotor with similar stator construction. Electric motor construction of induction motors britannica. The two factors that determine the speed of the weld, are the supply. Abstractthe paper presents a method to control the speed of doublyfed induction motors. Woundrotor induction motors are generally used for high torque and adjustable speed conditions. Wound rotor or slipring induction machines are commonly used in. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. Different speed control methods of induction motor are explained below.
Pole changing method is a speed control scheme of induction motor. In the case of a squirrel cage induction motor, the rotor is inaccessible and rotor circuit resistance is xed, whereas the wound. Pdf constant torque operation of wound rotor induction. The winding is placed evenly on slots of the rotor. Wound rotor induction motor, vsi with dynamic capacitor, rotor impedance control, hbridge capacitor switch. However, asynchronous motors do not inherently have the capability of variable speed operation. The principle of slip control is to control the speed of the motor by adjusting the rotor circuit, while the stator supply voltage and frequency remain constant. An843, speed control of 3phase induction motor using. Polyphase induction motors are mainly of two types by construction, squirrel cage and woundrotor with sliprings.
Based on the construction of the rotor, induction motors are broadly classified in two categories. With the wound rotor motor, the secondary resistors can be. In the second section, i would be throwing light on the operation and working principle of wound rotor induction motor. As induction motors are widely used, we will present the cheaper technique to control these motors. Rotor resistance speed control similar to rotor resistance starting, this method consists of varying the effective resistance in the rotor of a wound rotor induction motor to vary the speed.
The speed torque curves of the wound rotor induction motor. A wound rotor motor is used for constant speed applications requiring a heavier starting torque than is obtain able with the squirrelcage type. It follows that any eycient method of speed control must be based on varying the synchronous speed of the weld, rather than the slip. The operating point is the intersection of the two characteristics and we can fix for a given load and motor. The wound rotor motor is particularly effective in applications where using a squirrelcage motor may result in a starting current thats. In engineering practice it is frequently needed to. Wound rotor induction motor wrim speed torque curves, 282016. At lower speeds, either power is wasted in rotor resistanc. Speed control of wound rotor induction motor using rotor. Oct 03, 2016 what are the methods to control speed of wound rotor motors. Speed control of wound rotor induction motor using.
Wound rotor induction motor the engineering projects. Pdf this research article presents dynamic simulation of starting and speedcontrol of the woundrotor induction motor based on mathematical. Speed control at the rotor side we can change the speed at the rotor by,by adding some external resistance in the rotor circuitby cascade connection of the motor. Speed control methods for wound rotor ims electric. Pdf in a motor control, voltage saturation is a serious problem as a motor speed increases. An induction motor can therefore be made without electrical connections to the rotor.
As the motor approaches synchronous speed, f r becomes almost equal to f s and a nearly perfect revolving field is produces. When the rotor of ims is provided with a wound rotor, speed control is performed by. Speed control methods for wound rotor ims electric equipment. Speed control of wound rotor induction motors by ac regulator. Oct 10, 2016 a wound rotor induction motor is also known as slip ring induction motor. C series motors but this disadvantages of the induction motor can be overcome by slip ring induction motor. A constant speed motor would best suit certain applications, such as a constant speed wind turbine or a fluid pump. Woundrotor motors high torque and adjustable speed. There are different methods for controlling the speed. If you want to control induction motor speed, save yourself a lot of grief and get a 3phase motor. Speed control of wound rotor induction motor using rotor resistance control aim to use variable resistance in the rotor circuit to control wound rotor induction motor speed theory polyphase induction motors are mainly of two types by construction, squirrel cage and wound rotor with sliprings. Variants of this method include rotor power recovery systems using a second machine or.
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