Table of Contents
How does a slip ring motor works?
Slip rings on a wound rotor AC motor. Once the motor reaches operating speed, the brushes are lifted via the springs and the slip rings are short-circuited via the sliding contact bar. Adding resistance to the rotor windings brings the rotor current more in-phase with the stator current.
What is slip ring in induction motor?
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. Each pole is wired in series with a variable power resistor.
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.
Which method is used in slip ring induction motor?
A slip motor can be started by two different methods – the first method is called the current limiting method. The second method employed for starting of slip ring follows the modern slip ring technology and it is known as the definite time control.
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.
Why do we use slip rings in motors?
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 rotation while transmitting power or signals.
What is 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 are the advantages of slip ring induction motor?
Advantages: High Starting torque with low starting current. Speeds can be adjusted in the case of slip ring (wound rotor) induction motor by inserting an resistance. Slip ring motors have high over loading capacity, smooth acceleration under heavy loads, and no abnormal heating during starting.
What happens if the slip of induction motor is 1?
This is the reason; slip is never zero in an induction motor. Slip = 1, means that rotor is stationary. Negative value of slip in induction motor can be achieved when the rotor speed is more than the synchronously rotating magnetic flux.
What method of speed control is used on an AC slip ring motor?
There are two mechanisms to control speed, the first is through rotor rheostat control and the second is through cascade control. The objective of speed control can be achieved through the rheostat which in the first place is used to induce resistance in the system and set up the starting phase for motor slip ring.
How is slip speed calculated?
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.
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.
What is the difference between squirrel cage and slip ring induction motor?
The slip ring motor has brushes for transferring the power whereas the squirrel cage motor is brushless. The copper loss in the phase wound motor is high as compared to squirrel cage motor. The efficiency of the slip ring motor is low whereas the squirrel cage motor has high efficiency.
Which starter is suitable for 3 HP slip ring induction motor?
Solution: Slip ring induction motor Squirrel cage induction motor The rotor resistance starter can be used Rotor resistance starter cannot be used Starting torque is high Starting torque is low Brushes are present Brushes are absent Frequent maintenance is required Less maintenance required.
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.
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.
What is slip in DC motor?
Slip is the differentiation between synchronous and asynchronous speed. An AC (Alternating Current) induction motor consists of a stator and a rotor and the interaction of the currents flowing in the rotor bars and the rotating magnetic field in the stator generates the torque that turns the motor.
What is slip in AC motor?
“Slip” in an AC induction motor is defined as: As the speed of the rotor drops below the stator speed, or synchronous speed, the rotation rate of the magnetic field in the rotor increases, inducing more current in the rotor’s windings and creating more torque. Slip is required to produce torque.
What is the function of 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.
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.
What is difference between armature and commutator?
An armature is a combination of the winding, commutator, brushes, and ball bearings.What is Commutator? Armature Commutator It receives current from the armature windings It receives current from the armature core The core consists of armature windings, commutator, and brushes It has some segments.
