Improved characteristics of isolated network during starting of large induction motors

The motors being used on modem industrial systems arebecoming increasingly large in size . Starting of these largemotors , especially when working on isolated alternator , producesa transient voltage depression that can substantially reduce themotor output torque while severely influencing the operation ofany connected load .This study highlights the use of shunt capacitors to improve thecharacteristics of isolated network during the starting of largeinduction motor .,The analysis of the isolated system is carried out, firstly withoutusing the shunt capacitors and secondly with different sizes ofshunt capacitors . The alternator voltage variation, motor currentcharacteristics, capacitor characteristics and dynamicperformance are analyzed at different values of alternator fieldcurrent.The suitable value of the required shunt capacitor is obtained tomaintain the output voltage at the rated value during both startingand running conditions of the induction motor .The capacitor value is determined by two methods, the first isby compensating the alternator reactive volt ampere, while in the