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  • INTERVIEW QUESTIONS ELECTRICAL & ELECTRONICS ENGINEERING(EEE) DETAILS
    Question :
    Why field rheostat is kept in minimum position while armature rheostat at maximum position?
    Category Electrical & Electronics Engineering(EEE) Interview Questions
    Rating (0.3) By 63 users
    Added on 6/16/2011
    Views 411
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    Answers:

    In motors at the time of starting the armature resistance is introduced to reduce the high starting current and the field resistance is kept minimum to have high starting
    torque.



    In motor the speed of the motor is proportional to voltage and inversly proportional to flux in the field or field current.At the instant of starting to control the speed not to go beyond its rated value, the field rheostat is kept at minimum which means the flux flow through the field is maximum and field current is maximum so the speed will be in minimum and similarly when the armature rheostat is in maximum the voltage applied is minimum so does the speed which will also be minimum and u can bring the machine to its rated speed by controlling any one of this, that is either by increasing the applied voltage to the armature or by decreasing the current to the field



    Posted by: umesh prabhu    

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