Example DC Motor Drives

Example DC Motor Drives 1. A 200V, 10.5A, 10.5A, 2000 rpm shunt motor motor has the armature and field resistance of 0.5 and 00! respectivel". #he motor drive a load $hose tor%ue is a constant at rated motor tor%ue. Calculate motor speed if the source volta&e drops to 1'5V. 2. A 220V DC series series motor runs runs at 1000 rpm (cloc)$ise* and ta)es an armature current of 100 A $hen drivin& a load $ith a constant tor%ue. #he resistance of armature and +eld $indin&s are 0.05! each. ind the ma&nitude and direction of motor speed and armature current if the motor terminal volta&e is reversed and the num-er of turns in +eld $indin& is reduced to 0/. (assume linear ma&netic circuit*

ra)in& . A 200V, 10.5A, 10.5A, 2000 rpm shunt motor motor has the armature and field resistance of 0.5 and 00! respectivel". #he motor is operated under d"namic -ra)in& at t$ice the rated tor%ue and 00rpm. Calculate the value of -ra)in& current and resistor. (assume linear ma&netic circuit* lu&&in& . A 220V, 3'0 rpm, rpm, 100A DC separatel" separatel" excited excited motor has an armature resistance 0.05!. 4t is -ra)e -" plu&&in& from an initial speed 1000rpm. Calculate a. 6esistance to -e placed in armature armature circuit circuit to limit -ra)in& to t$ice the full load value. -. ra)in& ra)in& tor%ue, tor%ue, and

c. #or%ue $hen speed has fallen to 7ero

8peed control 5. 9ame three techni%ues that can control speed: ;. A 220V, 500A, ;00rpm separatel" excited motor has armature and field resistance of 0.02 and 10! respectivel". #he load tor%ue is &iven -" the expression T  2000 20 N , Nm  $here N is the speed in rpm. 8peed -elo$ rated are o-tained -" armature volta&e control and speed a-ove the rated are determine -" the +eld control. Calculate< a. Motor terminal volta&e and armature current $hen the speed is 50rpm -. ield $indin& volta&e and armature current $hen speed is '50rpm  L

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'. A 2=pole separatel" excited DC motor has ratin&s of 220V, 100A and '50rpm. 6esistance of the armature is 0.1!. #he motor has t$o field coils $hich are normall" connected in parallel. #he expression of the tor%ue to drive the load is &iven -" the expression T  500 0.3 N , Nm  $here N is the speed in rpm. 8peed -elo$ and a-ove rated are o-tained -" armature volta&e control and -" connectin& the t$o +eld $indin&s in series respectivel". Calculate< c. Motor armature current and speed $hen the armature volta&e is reduced to 110V d. Calculate the motor speed and current $hen +eld coils are connected in series.  L

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