A three-phase slip-ring induction motor, provided with a commutator winding, is shown in the figure. The motor rotates in clockwise direction when the rotor windings are closed.
If the rotor winding is open circuited and the system is made to run at rotational speed fr with
the help of prime-mover in anti-clockwise direction, then the frequency of voltage across slip
rings is f1 and frequency of voltage across commutator brushes is f2. The values of f1 and f2
respectively are
Q8.A 20-pole alternators is having 180 identical stator slots with 6 conductors in
each slot. All the coils of a phase are in series. If the coils are connected to realize
single-phase winding, the generated voltage is V1. If the coils are reconnected to
realize three phase star connected winding, the generated phase voltage is V2.
Assuming full pitch, single-layer winding, the ratio V1/V2is
Q9.The horizontally placed conductors of a single phase line operating at 50 Hz
are having outside diameter of 1.6 cm, and the spacing between centers of the
conductors is 6 m. The permittivity of free space is 8.854 × 10-12 F/m. The
capacitance to ground per kilometer of each line is