Since then a lot of improvement has taken place on the design of these two types of induction motors. Singlephase induction motor threephase induction motor singlephase induction motor there are probably more singlephase ac induction motors in use today than the total of all the other types put together. The stator construction is the same in both motors. The construction of a stator is the same for both the squirrel cage and slip ring induction motor. Performance characteristics of variablespeed slipring induction motor using chopper control in the rotor side article pdf available january 2018 with 500 reads how we measure reads. Woundrotor motors can be started with low inrush current, by inserting high resistance. The slip in an induction motor is the difference between the main flux speed and their rotor speed. The mechanism employed here is to control the speed via a single thyristor acting as an onoff switch at the rotor side of this slip ring induction motor. As we know the speed of induction motor, torque of induction motor, so, the speed of induction motor can be changed by changing synchronous speed or by changing the slip of induction motor and then parameter r2 and x2 are changed then torque remain constant and change in slip is affected in speed control. Pdf rotor side control of high power slip ring induction motor.
Speed control of three phase induction motor electrical. Adjusting the resistance allows control of the speed torque characteristic of the motor. Controlling number of stator poles to control n s c. The slip of the induction motor varies from 5 percent for small motors to 2 percent for large motors.
Squirrel cage induction motor squirrel cage induction motors are usually used in various industrial applications. The aim behind the development of the project is to limit the current at starting of motor and to develop the high starting torque. Synchronous speed of an induction motor is shown in equation 1. 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. Starting andcontrol of slipring 5 electrical engineering book. The traditional way to control the speed of a wound rotor induction motor is to increase the slip by adding resistance in the rotor. Ss 120 x f p 120 x 60 8 900 rpm rotor speed motor slip is known, equation 2. To start induction motor by rotor resistance starter 8. Speed control of induction motor detailed explanation. Speed control of 3phase induction motor microchip technology. Speed control of induction motor 7 ways to control induction.
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 woundrotorwith sliprings. Speed control in three phase induction motor mcqs with. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. Where slipring motors are employed whose only purpose is limiting the starting current or a limited speed control, the resistance or electrolyte method of starting is. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place.
Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. This method of speed control can only be applied to squirrel cage motor. Regulation of 3phase alternator by zpf and asa methods 9. 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. A slipring motor also requires a larger space for the motor and its controls. Speed control in three phase induction motor mcqs with answers. Various induction motor speed control methods advantages. This makes constant vf the most common speed control of an induction motor. Oct 04, 2017 3 phase motor with resistance type starter. External resistance control by using three rheostats doubly fed machine speed control by rotor. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load. If the slip ring induction motor is started with all the slip rings or the rotor terminals. It can control the speed of an induction motor over a range from as little as 5% of base speed up to about twice base speed. It is expressed by the percentage of synchronous speed.
The slip power dissipates in the external resistor in the slip ring induction motor. Speed control of induction motor using a modified chopper in the rotor circuit. This system cordinates with the motor during the motor startup and makes it available for process control. Slip power recovery system in three phase slip ring. Conventional methods of speed control of slip induction motor from rotor side, lead to. An induction motor can be defined as the ac electric motor device in which a power source fed by the alternating current with the help of a primary winding. The slip power is given back to supply network in the slip power recovery method or supply is given to auxiliary motor. Pdf performance characteristics of variablespeed slipring. The rotor terminals are connected to three slip rings which turn with the.
For slipring induction motors additional resistance can be coupled in series with the rotor circuit. Free download induction motor seminar ppt, pdf report. Electrical interview questions which motor is best. The slip ring motor has very little application in industries. There are different methods of starting of 3phase slip ring induction motor. The speed of the three phase induction should be lower than the synchronous speed when the power flow from rotor of the slip ring induction motor to the supply side. Learn more about the construction and operation of a slip ring induction motor. Three phase slip ring induction motor my tech info.
When a motor starts to rotate the slip is 100 % and the motor current is at maximum. A secondary use of the slip ring motor, is to provide a means of speed control. Almost 90% of induction motors are squirrel cage motors. Rotor chopper speed control this method is applicable to slip ring induction motors. 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. Synchronous speed is the speed at which the stator flux rotates. An843, speed control of 3phase induction motor using pic18 mcus. The most basic ways to control the speed of a slip ring induction motor is either from the. There are different methods of starting of 3phase slipring induction motor. Motor runs smoothly as the magnetic hum is reduced b. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Speed control of three phase induction motor electrical4u.
It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. Pdf a simple method of speed control of a three phase slip ring induction motor is accomplished by adding external variable. This slip power loss can be recovered and supplied back to improve the overall. Slip power recovery system for variable speed operation of. By using variable frequency control, it is possible to adjust the speed of the motor either above or below base speed. The change in speed depends upon both rotor circuit resistance and load. Speed control of wound rotor induction motor using rotor.
Adjusting the resistance allows control of the speedtorque characteristic of the motor. Rotor flux rotates slower than synchronous speed by the slip speed. 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 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.
Because the torque curve of the motor is effectively modified by the resistance. 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. Actual speed of an induction motor is given as n ns 1 s. Speed control of 3phase induction motor using pic18 microcontrollers. It may be used where, the induction motor is supplied by a dedicated generator so that frequency can be easily varied by changing the speed of prime mover. This can be used in starting a slip ring induction motor, for example. The synchronous speed of the motor is given by equation 1. A properly designed variable frequency induction motor drive can be very flexible. Starting and control of slipring induction motors electrical. A properly designed variable frequency inductionmotor drive can be very flexible. An843, speed control of 3phase induction motor using. Slip ring induction motor working principle electrical mastar. Know how to control the speed of slip ring motors bright. It can also be employed for marginal speed control.
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. If the slip power is utilized, the speed of the induction motor increases. The squirrel cage induction motor is the most popular type of ac motor. It is logical that the least expensive, lowest maintenance type motor should be used most often. It can control the speed of an induction motor over a range from as little as. Dec 17, 2019 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. As its name indicates stator is a stationary part of induction motor. The slip ring rotor chamber has two modification openings. Number of poles, frequencies and synchronous induction motor speed. Polyphase induction motors are mainly of two types by construction, squirrel cage and woundrotorwith sliprings. Generally, it is known as the asynchronous motor because its running speed is less than its synchronous speed. Therefore the efficiency of three phase induction motor is reduced by this method of speed control.
Slip ring induction motor working principle electrical. Adding an external resistant into rotor side circuit. The main motor is necessarily a slip ring induction motor but the auxiliary motor can be slip ring or squirrel cage induction motor. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. Pdf speed control of induction motor using a modified chopper. The motor can be started using grid rotor resistor.
General purpose slipring induction motors product catalogue. The difference of squirrel cage and slip ring induction motor is mainly on torque, speed, slip, resistance and reactance. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. A woundrotor 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. A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. Package solution for slip ring induction motor with variable speed control sprs is part of the complete package for motor starting process. In an induction motor, torque is equal to the power crossing the air gap divided by the synchronous mechanical speed. Put on the dc supply and run the dc motor of a speed close to the synchronous speed of.
As we know, the slip speed is the difference between the synchronous and rotor speed of the induction motor. Speed control of wound rotor induction motor using. But there is no restriction for the direction of phase rotation. When the induction motor speed requires greater than the synchronous speed, regenerative braking operation is necessary. The method which can be used for the speed control of induction motor from stator side is a. The different methods of speed control of induction motor can be broadly classified in to scalar and vector control methods. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv. It can improve mechanical performance, simplify system operation and eliminate damageprone wires dangling from movable joints. Rotor side control of high power slip ring induction motor using a. For slip ring induction motors additional resistance can be coupled in series with the rotor circuit. Percent slip is a way to measure the speed performance of an induction motor. This method is applicable to threephase slipring induction motor only. Three phase induction motor speed control from the rotor.
This method is applicable to threephase slip ring induction motor only. Hence, the synchronous speed changes with change in supply frequency. Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required. Induction motor seminar ppt, pdf report study mafia. By introducing external resistance in the rotor circuit, the speed of the motor can be reduced. The tendency of the rotor teeth to remain under the stator teeth due to direct magnetic attraction is reduced. Rotor side control of high power slip ring induction motor using a single thyristor. Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. When the injected voltage is in phase opposition with the induced rotor e. Stator winding can be either star or delta connected depending upon the design. Stardelta starting of a three phase induction motor 10. In this example, the slip rings have a brushlifting device and a sliding contact bar, allowing the slip rings to be shortcircuited when no longer required. Speed control of slip ring induction motors part ii.
It is logical that the least expensive, lowest maintenance type. The speed control of induction motor by considering to control on rotor side can subdivide into several speed controlling methods such as. A stator winding is placed in the stator of induction motor and the three phase supply is given to it. Based on the construction of the rotor, induction motors are broadly classified in two categories. They are especially suitable for heavy load inertia applications. The slip ring rotor was developed after a decade or so. Slip ring induction motors are widely used for high torque and variable speed applications. The speed listed on the motor nameplate is the base speed. Slip in electrical induction motors engineering toolbox.
Speed control in three phase induction motor mcqs with answers q1. Figure 3 shows the relation between the voltage and. Rotor induction motor an overview sciencedirect topics. Jul 07, 2018 speed control of slip ring induction motor is done by external resistance connected in the rotor side. A wound rotor, has a 3phase winding similar to the stator winding. It has already been stated that this is a common method used to limit the starting current of such machines. Sketch of a crosssection of slip rings for an electric motor. Speed control of induction motor 7 ways to control. The value of slip at full load varies from 6% in case of small motor and 2% in the large motor. Pdf performance characteristics of variablespeed slip. For satisfactory operation, motor a must be phase wound slip ring type with the stator to rotor winding ratio of 1.
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