Government Polytechnic 2010 Diploma in Hospital Management Electrical Machines - II - Question Paper

Q.1 (a) discuss how a rotating magnetic field is produced when a 3 phase
supply is provided to 3 phase winding.
07
(b) discuss the construction of 3 phase slip ring induction motor with the
help of neat diagram. tag the ports.
07
Q.2 (a) Why starter is needed to begin 3 phase induction motor? State
various kinds of starter used and discuss any 1 of them.
07
(b) State various methods of speed control of 3 phase induction motor.
discuss any 1 of them.
07
OR
(b) A six pole 3 phase 440 V, 50 Hz. Induction motor develops eight H.P. at
955 rpm, stator losses amount to 400 watts and the friction losses 0.5
H.P., compute (i) rotor copper loss (ii) efficiency of motor.
07
Q.3 (a) Why single phase motor is not self starting? State various method to
make itself begin and discuss any 1 of them.
07
(b) discuss with the help of diagram 2 field revolving theory applied to
single phase winding.
07
OR
Q.3 (a) State the kinds of altenator. Derive the e.m.f. formula of alternator. 07
(b) A six pole, three phase 50 Hz. Star connected alternator has 12 slots per pole
and four conductors per slot. The flux of 25 MWb enters the armature from
every north pole. compute the e.m.f. induced in the alternator. The coil
span is one to 10 and the distribution factor is 0.966.
07
Q.4 (a) describe the voltage regulation of an alternator. State various method to
determine voltage regulation of an alternator and discuss any 1 of them.
07
(b) Derive the formula of coil span factor and distribution factor related to
three phase A.C. armature winding.
07
OR
Q. four (a) Why 3 phase synchronous motor is not self starting? State the
various method of starting synchronous motor and discuss any 1 of
them.
07
(b) Draw the vector diagram of synchronous motor on load at different power
factor. obtain the internal angle if the resistance per phase is 0.3 ohms and
synchronous impedance per phase is three ohms.
07
Q.5 (a) discuss Universal motor and State its application 07
(b) discuss the construction and working of a Schrage motor. 07

Earning:   Approval pending.