What happens if load increases in induction motor?
1. The efficiency of the induction increases when the mechanical load increases because as the motors load increases, its slip increases, and the rotor speed falls. Since the rotor speed is slower, there is more relative motion between the rotor and the stator magnetic fields in the machine.
When load of induction motor increase its slip will?
Slip increases with increasing load – providing a greater torque. It is common to express the slip as the ratio between the shaft rotation speed and the synchronous magnetic field speed. When the rotor is not turning the slip is 100 %.
What happens when load increases on motor?
As the load is increased, the motor will slow down, and the torque will increase. Current into the motor will also increase. If the load is increased above the maximum, the motor may overheat after a while.
When the physical load driven by an induction motor is increased?
If there is no load torque, the load resistance is high and the rotor current is zero. With increased load, the load resistance is less and the current increases. In a three-phase induction motor, the rotating magnetic field of the stator passing through the rotor conductors induces a current in the rotor conductors.
Why does current increase when motor load increases?
If the mechanical load increases, the rotor stops a bit (since it’s harder for the rotor to rotate a heavier load), which decreases the counter-EMF. This reduction in the counter-EMF thus increases the current in the coil, and so the power needed from the external voltage source.
What is the importance of slip in 3-phase induction motor?
This is precisely the principle of operation of 3-phase induction motor. Slip creates a relative speed between the RMF and rotor. That keeps a torque continuously acting on it when the motor is running.
What are the types of load torque?
3 Types of Loads (Constant Torque/Constant Power/Variable Torque)
- Type 1 – CONSTANT TORQUE LOADS.
- Type 2 – CONSTANT POWER LOADS.
- Type 3 – VARIABLE TORQUE LOADS.
How does the motor speed change with increasing load?
Load Torque: For a fixed voltage, the speed of the motor is inversely affected by the load. Increase in load torque = decrease in speed.
Why does a motor draw more current under load?
As more mechanical load is applied, the motor slows, the back emf decreases, and more current is drawn. If sufficient mechanical load is applied, the motor stalls/stops rotating, and therefore there is no back EMF at all, and the current is limited by the supply or by the resistance of the windings.
How does an induction motor create more torque when a load is added?
An induction motor develops torque by inducing current to the rotor, which is proportional to the differential speed of the rotor and the rotating magnetic field in the stator. For NEMA design B motors the differential speed (called slip) is between 1% and 2% at full load.
Which method is used to speed control of induction motor?
By injecting EMF in rotor circuit
In this method, speed of an induction motor is controlled by injecting a voltage in rotor circuit. It is necessary that voltage (emf) being injected must have same frequency as of the slip frequency.
Why speed decreases as load increase in induction motor?
The speed of the motor is directly proportional to the EMF induces across the rotor terminal. This EMF causes flow of current in the rotor bars which causes torque over the rotor shaft . … In this way speed of the motor decreases with the increasing of load in rotor shaft…