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Abstract
In this paper attempt has been made towards verification of the fact presented in many books that armature-resistance control method of speed control leads to heavy power loss in the controlling rheostat which causes large decline in the efficiency of a DC Shunt Wound Motor. Experiments have been performed on a 3 H.P., 220V DC Shunt Motor at no-load condition. Speed of the motor is first obtained without any additional resistance. Speed is then changed by 200 r.p.m. in steps of 50 r.p.m. using Armature-Resistance Control and Field-Resistance Control methods. Efficiency of the motor is calculated at different speeds using each method.