Recent questions and answers in DC machine

0 answers 29 views
1 answer 22 views

A DC shunt motor has rated rpm of 480. Certain industrial application requires this motor to run at 540 rpm for some time. Which speed control will be desirable? A) Ward Leonard control B) Armature current control C) Field resistance control D) It is not possible to run the motor at more than the rated rpm 

answered Jun 17, 2018 in DC machine
0 answers 10 views

The induced emf in the armature of a wave wound 4-pole d.c. machine having 100 armature conductors rotating at 600 r.p.m. and with a flux of 1 Wb per pole is (a) 1000 V (b) 2000 V (c) 200 V (d) 100 V

asked May 25, 2018 in DC machine
1 answer 29 views

A separately excited d.c. machine is coupled to a 50 Hz, three-phase, 4-pole induction machine as shown in the figure. The Dc machine is energized first and the machines rotate at 1 600 1pm. Subsequently the induction machine is also connected to a 50 Hz, three phase source, the phase sequence being consistent with the direction of rotation. In steady state

answered May 20, 2018 in DC machine
1 answer 17 views

A 50 kW dc shunt is loaded to draw rated armature current at any given speed. When driven  (i) at half the rated speed by armature voltage control and (ii) at 1.5 times the rated speed by field control, the respective output powers delivered by the motor are approximately. (A) 25 kW in (i) and 75 kW in (ii) (B) 25 kW in (i) and 50 kW in (ii) (C) 50 kW in (i) and 75 kW in (ii) (D) 50 kW in (i) and 50 kW in (ii)

answered May 17, 2018 in DC machine
1 answer 14 views

In a DC machine, which of the following statements is true ?  (A) Compensating winding is used for neutralizing armature reaction while interpole winding is used for producing residual flux (B) Compensating winding is used for neutralizing armature reaction while interpole winding is used for improving ... winding is used for neutralizing armature reaction (D) Compensation winding is used for improving commutation while interpole winding is used for producing residual flux

answered May 17, 2018 in DC machine
1 answer 38 views

What are the slot wedges in a DC machine made of?   (a) Mild steel (b) Silicon steel (c) Fibre (d) Cast iron

answered May 13, 2018 in DC machine
1 answer 21 views

For continuously running rolling mills with intermittent loading, the most suitable DC drive is   (a) DC series motor (b) DC shunt motor (c) DC differentially compound motor (d) DC cumulatively compound motor 

answered May 13, 2018 in DC machine
1 answer 17 views

Fractional pitch windings are used in DC machines to (A) Reduce copper losses (B) Improve cooling (C) Increase the generated emf (D) Reduce sparking

answered May 12, 2018 in DC machine
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