Why is the air gap between the stator and the rotor so small?
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.
What is the gap between stator and rotor?
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 [9]. The smaller the air gap, the lower the starting current drawn by the motor.
What happens when there is a large air gap between the rotor and stator?
The longer air gap thickness between the motor stator and the rotor, the more cooling liquid flowing through the air gap, which results the heat exchange becomes better between the motor and the cooling liquid and the temperature rise of the motor is lower.
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 [3].
How do I check the air gap on my alternator?
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). While they can point to an air gap, they cannot always reveal if it is getting worse over time and how much eccentricity is actually present.
What happens if the air gap length of induction motor is doubled?
What happens if the air gap length is doubled? If the air gap of an induction motor is doubled then the mmf and magnetizing current approximately doubles. Also increase in air gap length increases the overload capacity, offers better cooling, reduces noise and reduces unbalanced magnetic pull.
What is the length of the air gap?
Calculation of Length of air Gap: Length of the air gap is usually estimated based on the ampere turns required for the air gap. Suitable value of SCR must be assumed. Ampere turns required for the air gap will be approximately equal to 70 to 75 % of the no load field ampere turns per pole.
In which type of rotor the air gap is uniform?
2. Cylindrical Pole Alternator: Unslotted portion of the cylinder acts as poles hence poles are non-projecting. The air gap is uniform due to the smooth cylindrical periphery.
What will be the effect on an alternator if length of air gap is increased?
Longer air gap means increased reluctance and leakage flux. Therefore the value of air gap flux reduces. This in turn reduces EMF induced in the rotor bars, rotor current and torque. Apart from this, longer air gap length will also cause to have poor power factor and hence associated losses will also increase.
What is the physical air gap between the rotor and stator?
The physical air gap between the rotor or armature and the stator or field frame is complex and plays a critical role in the performance of AC and DC machines. Most repairers do not realize how little they understand about this subject.
How much air gap length should be in an alternator?
It can be checked by inserting a plastic feeler gauge between the stator and rotor. It should be uniform all round. Originally Answered: how much air gap length in alternator? It should be as small as possible to reduce the eddy current losses due to leakage flux and large gap will increase the windage losses.
What causes air gap in electric motor rotors?
Most motor design and repair professionals recommend that air gap variation should never exceed +/- 10% of the average air gap. So, what causes air gap in electric motors? There can be a variety of underlying causes, including obvious ones like a bent shaft, cocked bearings, or out-of-roundness of either the rotor or stator during manufacturing.
What happens if the rotor hits the stator?
In addition, if the rotor is eccentric relative to the stator and the air gap is too small, the stiffness of the shaft might be overcome by the resulting unbalanced magnetic pull. This, in turn, leads to damage resulting from the rotor striking the stator as it is pulled out of place by the magnetic forces.