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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. Adjusting the resistance allows control of the speed/torque characteristic of the motor.
How does a slip ring motor work?
Working of Slip Ring Induction Motor When a stator winding is excited with an AC supply, the stator winding produces magnetic flux. Based on faraday’s law of electromagnetic induction, the rotor winding gets induced and generates a current of magnetic flux. The slip ring induction motor diagram is shown below.
What is the use of slip ring in induction motor?
In a version of the AC induction motor referred to as a wound rotor motor, slip rings are used not for transferring power, but for inserting resistance into the rotor windings. A wound rotor motor uses three slip rings — typically made of copper or a copper alloy — mounted to (but insulated from) the motor shaft.
How do you control the speed of a slip ring motor?
Speed Control by Rotor Rheostat Control With the same rheostat added to the rotor circuit, it is possible to regulate the speed of slip ring motors. The resistance is engaged maximum during starting and slowly cut-off to increase the speed of the motor.
What is the difference between slip ring and commutator?
The main difference is that commutator is used for the conversion of AC to DC. Slip rings are used in AC motors to provide a continuous transfer of power whereas the commutators are used in DC motors to reverse the polarity of the current in the armature windings.
What is the difference between induction motor and slip ring motor?
In Squirrel cage induction motors the rotor is simplest and most rugged in construction. In slip ring induction motors the rotor is wound type. In the motor the slip rings, brushes are provided. Compared to squirrel cage rotor the rotor construction is not simple.
What is the function of a slip ring commutator?
A commutator is a specialized slip ring typically used on Direct Current motors and electrical generators to transfer electrical power between the stationary housing and the rotating armature with the added purpose of reversing the electrical current direction.
What is slip formula?
If the revolving magnetic flux’s synchronous speed & the speed of rotor are Ns & Nr in the motor, then the speed among them can be equivalent to (Ns – Nr). So, slip can be determined as. S = (Ns – Nr) / Ns.
What is motor slip formula?
Slip speed is the speed difference between the Synchronous speed and Rotor speed. Slip speed = Synchronous speed – Rotor speed = Ns -N. Slip, s = (Ns – N) / Ns.
Which starter is used for slip ring induction motor of high ratings?
For slip ring induction motors with high ratings, a rotor resistance starter is utilised.
Why are slip rings used?
“A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. A slip ring can be used in any electromechanical system that requires unrestrained, intermittent or continuous rotation while transmitting power and / or data.
What type of motor uses slip rings?
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. Adjusting the resistance allows control of the speed/torque characteristic of the motor.
What is V F method?
A control method that enables preventing reductions in the power factor or efficiency of a motor in a wide range of variable speed operation for changes in the frequency for speed control by outputting a voltage (V/f characteristic) corresponding to the frequency set by a parameter in an Inverter.
What determines the method of controlling motor speed?
Thus, the speed of a DC motor can be controlled in three ways: By varying the supply voltage. By varying the flux, and by varying the current through the field winding. By varying the armature voltage, and by varying the armature resistance.
What are the methods of speed control of induction motor?
Speed Control of Induction Motor from Stator Side By Changing the Applied Voltage. By Changing the Applied Frequency. Constant V/F Control of Induction Motor. Changing the Number of Stator Poles. Rotor Rheostat Control. Cascade Operation. By Injecting EMF In Rotor Circuit.
Do DC motors have slip rings?
In a d.c electric motor, the commutators are used instead of slip rings. The commutators are similar to the slip rings but have critical distinctions. In the d.c motors, commutators are used to reverse the polarity of current in the armature coils.
Why do we use slip rings in AC generator?
The function of slip ring in an AC generator is that these are the hollow rings that are connected to the ends of the armature coil. They help in rotation of the coil. A slip ring in an electric motor is used an electrical joint to transmit power. It acts as a bridge between a still component and a rotating element.
Does a DC generator have slip rings?
In construction, a dc generator is similar to a motor, or even an ac generator, with the addition that slip rings are replaced by split rings. Its three main parts are: A rotating loop of coil. A permanent magnet.
Can induction motor run at synchronous speed?
So, theoretically, the Induction motor can never run at synchronous speed. But due to the reduction of speed, again lag influx will be achieved, and the motor will continue to move at this speed due to flux difference between rotor and stator. In short, an induction motor cannot run at induction speed.
What are the two types of rotors?
There are two types of induction motor rotors: Squirrel-cage rotor or simply cage rotor. Phase wound or wound rotors.
Are induction motors self starting?
The single-phase induction motor is non self-starting in nature. When single phase AC supply is given to stator winding of single-phase motor, it produces alternating flux i.e. which alternates along one space axis only. It is not synchronously revolving (or rotating) flux, thus it cannot produce any rotation.
