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Where speed-current characteristic of DC shunt motor lies with respect to DC cumulative compound motor (assume current smaller than full load current)?(a) Can be represented by same curve(b) Above(c) Below(d) Cannot be determinedThe question was posed to me at a job interview.My question is based upon Operating Characteristics of DC Compound Motor in portion Characteristics of DC Motors of DC Machines

Answer»

Right answer is (c) Below

Easy EXPLANATION: At start, SPEED of DC cumulative motor is more than the speed of shunt motor because of series CHARACTERISTIC effect. Because of φse increasing with Ia beyond full load CURRENT, the speed of the compound motor falls much more SHARPLY than the shunt motor.



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