E4102- DC MOTOR CONTROL(ANSWER) Kuiz 4

CODE/MODULE: E4102- DC MOTOR CONTROL

Kuiz 4 (10 marks)

1.  TWO advantages(2) dc supply.             

                                               i.    Dc motor suitable used for variable speed.

                                              ii.    Most of DC components  are lighter and more efficient.

                                            iii.    DC system- not interference communication lines.

                                                                                                                    (2x1 = 2 marks)

     TWO disadvantages(2) dc supply

                                               i.      Power feeder installation is quite hard.

                                              ii.      Hard to change the voltage value.

                                            iii.      Hard to find the components with high rate.

                                                                                                                   (2x1 = 2 marks)

 2. DC series motor rated value - 150hp, 1500rpm, 600V. I_load =200A Ra +Rf = 0.1W.

V_line = 700VAwitching frequency = 50Hz to1600Hz and t ON = 600ms.  

   i.   Chopper frequency     

                        Va₁   =  200 x 0.1   =  20V.

           When Va = 700V. motor is stationary and back emf = 0.

           Va₁    =   VafTa

           20      =  700f600mS

             f       =  47.62Hz.                                                                            (2 marks)

    ii.   Chopper current when. I_load =240A

                      Va₁   =  240 x 0.1   =  24V.

                 P  =  VI   =  24 x 240    =  5.76kW.

             I  chopper  =  5.76/700     =  8.23A.                                               (2 marks)

   iii.  Chopper frequency at rated value

                            Va₁   =   VafTa

                            600   =   700f600mS

                              f      =    1429Hz.                                                            (2 marks)