This makes constant vf the most common speed control of an induction motor. This system cordinates with the motor during the motor startup and makes it available for process control. 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. Stardelta starting of a three phase induction motor 10. Rotor side control of high power slip ring induction motor using a. Slip power recovery system for variable speed operation of. If the slip power is utilized, the speed of the induction motor increases.
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. Electrical interview questions which motor is best. The rotor terminals are connected to three slip rings which turn with the. The traditional way to control the speed of a wound rotor induction motor is to increase the slip by adding resistance in the rotor. Speed control of induction motor 7 ways to control induction. The slip ring motor has very little application in industries. Woundrotor motors can be started with low inrush current, by inserting high resistance. Wound rotor induction motors with three rotor slip rings have been used in adjustable speed drives for many years. Speed control of induction motor using a modified chopper in the rotor circuit. Pdf a simple method of speed control of a three phase slip ring induction motor is accomplished by adding external variable. Slip ring induction motors are widely used for high torque and variable speed applications.
To start induction motor by rotor resistance starter 8. Almost 90% of induction motors are squirrel cage motors. There are different methods of starting of 3phase slipring 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. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load. The squirrel cage induction motor is the most popular type of ac motor. 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. Speed control of three phase induction motor electrical4u. Speed control in three phase induction motor mcqs with. The different methods of speed control of induction motor can be broadly classified in to scalar and vector control methods. Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required.
Pdf performance characteristics of variablespeed slipring. Regulation of 3phase alternator by zpf and asa methods 9. It can control the speed of an induction motor over a range from as little as. When the injected voltage is in phase opposition with the induced rotor e. A properly designed variable frequency inductionmotor drive can be very flexible. Slip power recovery system in three phase slip ring.
Three phase slip ring induction motor my tech info. Synchronous speed of an induction motor is shown in equation 1. Speed control of induction motor detailed explanation. 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. By introducing external resistance in the rotor circuit, the speed of the motor can be reduced. Jul 07, 2018 speed control of slip ring induction motor is done by external resistance connected in the rotor side. They are especially suitable for heavy load inertia applications. If the slip ring induction motor is started with all the slip rings or the rotor terminals. Stator winding can be either star or delta connected depending upon the design. Since then a lot of improvement has taken place on the design of these two types of induction motors. Speed control of slip ring induction motors part ii. The slip in an induction motor is the difference between the main flux speed and their rotor speed. An843, speed control of 3phase induction motor using pic18 mcus. Generally, it is known as the asynchronous motor because its running speed is less than its synchronous speed.
The most basic ways to control the speed of a slip ring induction motor is either from the. The stator construction is the same in both motors. Oct 04, 2017 3 phase motor with resistance type starter. As its name indicates stator is a stationary part of induction motor. Rotor flux rotates slower than synchronous speed by the slip speed. 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. The speed listed on the motor nameplate is the base speed.
Put on the dc supply and run the dc motor of a speed close to the synchronous speed of. 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. 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. Speed control in three phase induction motor mcqs with answers q1. Polyphase induction motors are mainly of two types by construction, squirrel cage and woundrotorwith sliprings. A secondary use of the slip ring motor, is to provide a means of speed control. Slip ring induction motor working principle electrical mastar. Jan 09, 2017 speed control by varying rotor resistance.
The slip ring rotor chamber has two modification openings. Motor runs smoothly as the magnetic hum is reduced b. Starting and control of slipring induction motors electrical. Know how to control the speed of slip ring motors bright.
It can improve mechanical performance, simplify system operation and eliminate damageprone wires dangling from movable joints. Pdf rotor side control of high power slip ring induction motor. The slip power is given back to supply network in the slip power recovery method or supply is given to auxiliary motor. 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. It is logical that the least expensive, lowest maintenance type.
A properly designed variable frequency induction motor drive can be very flexible. The synchronous speed of the motor is given by equation 1. Various induction motor speed control methods advantages. 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. Controlling number of stator poles to control n s c. Hence, the synchronous speed changes with change in supply frequency. Therefore the efficiency of three phase induction motor is reduced by this method of speed control.
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. Synchronous speed is the speed at which the stator flux rotates. Ss 120 x f p 120 x 60 8 900 rpm rotor speed motor slip is known, equation 2. Slip in electrical induction motors engineering toolbox. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. The slip power dissipates in the external resistor in the slip ring induction motor. Speed control of wound rotor induction motor using. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. A wound rotor, has a 3phase winding similar to the stator winding. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. Pdf speed control of induction motor using a modified chopper.
Speed control of 3phase induction motor using pic18 microcontrollers. The change in speed depends upon both rotor circuit resistance and load. Slip ring induction motor working principle electrical. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv. Speed control of 3phase induction motor microchip technology. Squirrel cage induction motor squirrel cage induction motors are usually used in various industrial applications. Package solution for slip ring induction motor with variable speed control sprs is part of the complete package for motor starting process. Pdf performance characteristics of variablespeed slip. This method is applicable to threephase slipring induction motor only.
Adjusting the resistance allows control of the speedtorque characteristic of the motor. This can be used in starting a slip ring induction motor, for example. Learn more about the construction and operation of a slip ring induction motor. Rotor chopper speed control this method is applicable to slip ring induction motors. External resistance control by using three rheostats doubly fed machine speed control by rotor. Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. 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. Rotor induction motor an overview sciencedirect topics.
Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. Adding an external resistant into rotor side circuit. Speed control of wound rotor induction motor using rotor. The slip of the induction motor varies from 5 percent for small motors to 2 percent for large motors. This slip power loss can be recovered and supplied back to improve the overall. For slipring induction motors additional resistance can be coupled in series with the rotor circuit. The construction of a stator is the same for both the squirrel cage and slip ring induction motor.
Actual speed of an induction motor is given as n ns 1 s. It is logical that the least expensive, lowest maintenance type motor should be used most often. Speed control in three phase induction motor mcqs with answers. By using variable frequency control, it is possible to adjust the speed of the motor either above or below base speed.
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. Because the torque curve of the motor is effectively modified by the resistance. For slip ring induction motors additional resistance can be coupled in series with the rotor circuit. The slip ring rotor was developed after a decade or so. 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.
This method of speed control can only be applied to squirrel cage motor. 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. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Lot of research work has been carried out to improve its power factor and to achieve suitable methods of speed control. When a motor starts to rotate the slip is 100 % and the motor current is at maximum.
The aim behind the development of the project is to limit the current at starting of motor and to develop the high starting torque. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. The difference of squirrel cage and slip ring induction motor is mainly on torque, speed, slip, resistance and reactance. 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. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. But there is no restriction for the direction of phase rotation. For satisfactory operation, motor a must be phase wound slip ring type with the stator to rotor winding ratio of 1. If the motor slip is known, the rotor speed can be expressed by the equation.
The motor can be started using grid rotor resistor. 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. Percent slip is a way to measure the speed performance of an induction motor. A stator winding is placed in the stator of induction motor and the three phase supply is given to it. Rotor side control of high power slip ring induction motor using a single thyristor. The tendency of the rotor teeth to remain under the stator teeth due to direct magnetic attraction is reduced. The speed control of induction motor by considering to control on rotor side can subdivide into several speed controlling methods such as. In a current limiting method the closing of contactors at each step is. 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 three phase induction motor electrical.
Based on the construction of the rotor, induction motors are broadly classified in two categories. Speed control of induction motor 7 ways to control. The method which can be used for the speed control of induction motor from stator side is a. There are different methods of starting of 3phase slip ring induction motor.
In an induction motor, torque is equal to the power crossing the air gap divided by the synchronous mechanical speed. An843, speed control of 3phase induction motor using. This method is applicable to threephase slip ring induction motor only. Figure 3 shows the relation between the voltage and. The main motor is necessarily a slip ring induction motor but the auxiliary motor can be slip ring or squirrel cage induction motor. The value of slip at full load varies from 6% in case of small motor and 2% in the large 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. It has already been stated that this is a common method used to limit the starting current of such machines. Three phase induction motor speed control from the rotor. Free download induction motor seminar ppt, pdf report. Adjusting the resistance allows control of the speed torque characteristic of the motor.
Induction motor seminar ppt, pdf report study mafia. Number of poles, frequencies and synchronous induction motor speed. It can also be employed for marginal speed control. It is expressed by the percentage of synchronous speed.
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