In motors the number of rotor slots and stator slots are different and thus cogging (magnetic locking) can’t happen. And thus The slip motor can’t run at rated speed. Torque developed by induction motor is proportional to the slip. At synchronous speed,slip is zero and hence torque developed by the motor is zero.
What causes motor slip?
The interaction of currents flowing in the rotor bars and the stators’ rotating magnetic field generate torque. In actual operation, rotor speed always lags the magnetic field’s speed, allowing the rotor bars to cut magnetic lines of force and produce useful torque. This speed difference is called slip speed.
What happens when slip is zero?
Zero slip means that rotor speed is equal to synchronous speed. If rotor is rotating at synchronous speed in the direction of rotating magnetic field the, there will be no flux cutting action, no emf in the rotor conductors, no current in rotor bar conductor and hence no development of electromagnetic torque.
Why it is necessary to maintain the slip?
Importance of Slip
The torque is directly proportional to the rotor current. Hence, torque is directly proportional to slip. The above equation shows that the torque induces on the rotor is directly proportional to the slip of the induction motor. The high value of slip induces the emf in the rotor.
What is slip in AC motor?
Slip is the differentiation between synchronous and asynchronous speed. … The difference between the synchronous speed of the electric motor magnetic field, and the shaft rotating speed is slip – measured in RPM or frequency. Slip increases with increasing load – providing a greater torque.
Can slip be negative?
If the rotor of an induction machine rotates above synchronous speed, slip is negative, as are torque, mechanical output power and air gap power. … If slip is negative, the “input power” to the electrical terminals will be negative, implying that power is flowing out of the electrical terminals.
Do synchronous motors have slip?
Do synchronous motors have slip? Because the rotor turns at the same speed as synchronous speed (speed of the rotating magnetic field), there is no slip. The speed of rotation of the motor is constant in a synchronous motor, and does not vary with load, as in an induction motor.
What is full load slip?
At full load the speed of the motor is 1350 rpm. Hence slip at full load = 5.33% When the motor is so loaded that the rotor speed is reduced to 0, the value of Slip is 1. Hence, value of Slip gradually increases from no-load to full load.
What is the value of slip at starting?
So the rotor in the motor begins revolving with a speed which is known as actual speed (N). The main disparity between the synchronous & actual speed is known as the SLIP. The slip value is equal to ‘1’ as the rotor in the motor is at rest & it will not equivalent to ‘0’.
What is the slip frequency?
What is slip frequency? slip frequency may be defined as the difference between the frequency corresponding to the synchronous speed and the frequency corresponding to the rotor speed(other than Ns) mathematically, (Ns-N)*P/120 , where Ns is synchronous speed and N is the rotor speed in rpm and P is the no.
What is slip formula?
Formula to find slip = (ns – n) x 100/ns. substitute the values in the above formulas. speed difference = 1500 – 1450. = 50.
What is synchronous speed and slip?
Slip is the difference between the synchronous speed of a motor and its actual speed. Mathematically it is determined by. Slip = Synchronous Speed − Actual Speed. Using the example above for synchronous speed of a motor with four poles operating at 60 hertz, the value was calculated to be 1800 RPM.
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 is difference between slip ring and commutator?
Physically, a slip ring is a continuous ring, whereas a commutator is segmented. Functionally, slip rings provide a continuous transfer of power, signals, or data. … Commutators, on the other hand, are used in DC motors to reverse the polarity of current in the armature windings.
What is synchronous speed?
: a definite speed for an alternating-current machine that is dependent on the frequency of the supply circuit because the rotating member passes one pair of poles for each alternation of the alternating current.
Why slip ring is used 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. Also, they provide electric contact with the brushes. … A slip ring in an electric motor is used an electrical joint to transmit power.