Why is there an air gap between rotor and stator?
The smaller the air gap is, the lower that reluctance, and thus the higher the magnetic flux (which is the magnetic analog of current), allowing the motor to work more efficiently and at a higher power.
Why does the air gap between stator and rotor of induction motor keep small?
Detailed Solution. The presence of air-gap between the stator and rotor of an induction motor increases the reluctance of the magnetic circuit. … That is why the small air-gap is preferred for the induction motor which helps to reduce the magnetizing current.
What is the fault when the air gap between the rotor and stator of a machine is not uniform?
Air gap eccentricity is known as a condition that occurs when there is a non-uniform or asymmetric distance between the rotor and stator in the air gap. When there is an eccentricity in the air gap, the permeance in the air gap varies, causing unbalanced magnetic flux within the air gap .
What is the value of air gap of induction motor?
The number of slots/pole/phase should not be less than 2 otherwise the leakage reactance becomes high. The number of slots should be selected to give an integral number of slots per pole per phase. The stator slot pitch at the air gap surface should be between 1.5 to 2.5 cm.
What is the use of checking the air gap between stator and rotor in an induction motor?
There are three methods that can be used to reveal the presence of an air gap: MCA (Motor Circuit Analysis), CSA (Current Circuit Analysis), and RIC (Rotor Influence Check). … Air gap size and uniformity is bigger issue with large motors and large motor repair.
What is the synchronous speed when F 60hz P 6?
The synchronous speed of 60 Hz, 4 Pole Induction Motor is: 900 RPM.
What happens if the air gap becomes more or less?
With an increase in air gap length, the more magnetizing current is required to produce the rated flux in the magnetic core, and the phase angle between the applied voltage and the magnetizing current increases. As a result, the power factor becomes low.
When air gap is increase in induction motor?
If the air gap of an induction motor increases, 1) The permeability of the magnetic circuit rotor-to-stator will decrease. 2) The magnetizing inductance of the motor thus decreases. 3) The magnetizing current will increase; This will cause a poor power factor at all loads.
What is the length of the air gap?
For small PM synchronous motors, the air gap (mechanical clearance) between the stator core and rotor poles or pole shoes should be 0.3 to 1.0 mm [6,8], and can even reach 1.5 mm . The smaller the air gap, the lower the starting current drawn by the motor.
Why is air gap kept low in rotating machine?
Why Air Gap Length is kept Minimum for Induction Machine? … The induced EMF in the rotor winding or rotor bars is due to mutual induction caused from the rotating magnetic field produced by the stator winding. Thus, an IM can be treated as a Rotating Transformer as the EMF induced in the rotor is by Mutual Induction.