As load increases, it needs to generate torque to drive the load. This is possible only if an induced current flows in the rotor and this requires that a slip must exist between the rotor speed and the synchronous speed. … Thus we can say that an induction motor is a nearly constant speed motor.
Why a synchronous motor is a constant speed motor?
In the synchronous motor, rotor too have a DC excitation, so it produces a constant flux forming the electromagnetic poles on rotor which initially are stationary. … Even on loading, the speed is always constant but the torque angle (between stator and rotor magnetic poles) may vary.
Which motor is used for constant speed?
DC shunt motor
What is the difference between induction motor and normal motor?
The stator winding of Induction Motor is energized from an AC source. Synchronous Motor always runs at synchronous speed, and the speed of the motor is independent of load, but an induction motor always runs less than the synchronous speed. If the load increased the speed of the induction motor decreases.
What are the advantages of synchronous motor?
The advantages of the synchronous motor are the ease with which the power factor can be controlled and the constant rotational speed of the machine, irrespective of the applied load. Synchronous motors, however, are generally more expensive and a d.c. supply is a necessary feature of the rotor excitation.
What is the speed of synchronous motor?
At 60 Hz: A two-pole/phase synchronous ac motor turns at 3,600 RPM. A four-pole/phase synchronous ac motor turns at 1,800 RPM.
Which motor has the poorest speed control?
Which DC motor is preferred for constant speed?
Explanation: Rotary compressor generally demand constant speed operation throughout the load. Sometimes, DC machines are not able to produce constant speed throughout the process hence, synchronous machine is used. 4.
What is a DC shunt motor?
A DC shunt motor (also known as a shunt wound DC motor) is a type of self-excited DC motor where the field windings are shunted to or are connected in parallel to the armature winding of the motor. Since they are connected in parallel, the armature and field windings are exposed to the same supply voltage.
What causes the induction motor to slow down?
That change frequency and because of that change in frequency speed of induction motor change. … If you reduce the line voltage, the motor will slow down because you have weakened the stator field, but how much it slows down is directly related to the hp rating of the motor and the load it is driving.
How can we reduce rpm of motor?
The load to be driven by the shaft will often require a different speed or torque or will require the transmission of power to an adjacent shaft. Reducing RPM can be accomplished by using two or more pulleys and belts to transmit and change the speed of rotation.
How does an induction motor start?
When the supply is connected to the stator of a three-phase induction motor, a rotating magnetic field is produced, and the rotor starts rotating and the induction motor starts. … At the time of starting, the motor slip is unity, and the starting current is very large.
What is the function of induction motor?
An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor.