y1 - lt 1 - 5; y2\nac motors quiz #1a\ntotal = _/16\nname: khador\n1. 3 what are the 3 main constructional…

Brief Explanations:

1. The three main constructional parts of a three - phase induction motor are the stator, rotor, and air - gap. The stator provides the magnetic field, the rotor is the rotating part, and the air - gap separates them.
2. When comparing to a transformer, the stator winding is similar to the primary winding (which receives the input voltage), and the rotor circuit is similar to the secondary winding (which delivers the output).
3. Synchronous speed is the speed at which the rotating magnetic field in an AC machine rotates. It is given by $n_s=\frac{120f}{P}$, where $f$ is the frequency of the supply and $P$ is the number of poles.
4. To reverse the direction of rotation of a three - phase induction motor, any two of the three - phase supply lines are interchanged. This changes the phase sequence of the supply, which in turn changes the direction of the rotating magnetic field.
5. Increasing slip increases the rotor reactance. As slip $s=\frac{n_s - n}{n_s}$, and rotor reactance $X_r = sX_{r0}$ (where $X_{r0}$ is the rotor reactance at standstill). So as $s$ increases, $X_r$ increases.
6. Increasing the rotor circuit resistance of a wound - rotor induction motor increases its starting torque because it shifts the maximum torque point to a higher slip value. At starting (when slip $s = 1$), a higher resistance allows more current to flow in the rotor circuit in phase with the induced emf, thus increasing the starting torque.

Answer:

1. Stator, Rotor, Air - gap
2. Primary, Secondary
3. The speed at which the rotating magnetic field in an AC machine rotates ($n_s=\frac{120f}{P}$)
4. Interchange any two of the three - phase supply lines
5. Increases rotor reactance
6. Shifts the maximum torque point to a higher slip value and allows more in - phase current in the rotor circuit at starting