Table of Contents
What is air gap line in DC machine?
The air gap refers to an actual physical gap in an electric motor that separates the moving rotor and the stator core. This gap is a necessary part of motor design and the size of the air gap is one of the keys to motor performance and reliability.
What is sinusoidal flux?
Flux is dot product of two vector quantities B and A. So sinusoidal flux will be B.A=k1. sin( k2*t) where k1 and k2 are constants. This is possible in many ways. Let’s take a case where B is produced from solenoid passing ac current.
How the flux is distributed in DC machine?
In dc machines, the armature reaction causes a distorted flux-density distribution in the air gap. Figure 1 shows the magnetic field produced in the air gap of a two-pole dc motor or generator by (a) the field mmf, (b) the armature mmf, and (c) both armature and field mmf acting together.
Why is the air gap between the stator and the rotor so small?
The purpose of air gap is to allow relative motion between stator and rotor. So it should be as small as possible. A large air gap demands more field ampere turns to produce a given flux in the air gap. So the size of the machine will increase.
Where is the air gap in DC generator?
According to The Electro-mechanical Authority (EASA), in AC machines, the air gap is the air space between the rotor cores and the stator. On the other hand, it is said to be the space between the inter-poles and the armature for a DC machine.
What happens if the air gap flux density in an induction motor increase?
Detailed Solution. 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.
Why is AC sinusoidal?
The AC current that powers your home happens to be sinusoidal because the generators we use produce sinusoidally varying currents by default. It is easier to use it as it is produced than convert it to something else. The net power in an AC cycle is not zero because power is a function of the square of the current.
What is the effect on induced emf if the main field flux get distorted in dc generator?
The adverse effects of armature reaction: In case of a dc generator, weakening of the main flux reduces the generated voltage. Armature reaction distorts the main flux, hence the position of M.N.A. gets shifted (M.N.A. is perpendicular to the flux lines of main field flux).
What will happen if the back emf of dc motor vanishes?
If back emf of a dc motor vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows.
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 function of air gap?
When installed and maintained properly, the air gap works as described above, and prevents drain water from the sink from backing up into the dishwasher, possibly contaminating dishes.