Study of Smooth Starting for LT/HT 3-phase Induction Motors by Using HFSR Starter Method for Specially Pumping Application

Abstract: When three phase induction motor greater than 50 kW take very large currents with surge started directly from a 3phase supply. Actually soft starts are used for reducing this problem and to achieve smooth starting of large capacity induction motors. This will be a very useful strategy especially in Industries where various induction motors of large capacity are regularly started from a 3-phase supply. The control of soft starting is useful for prolonging the life of electric contact and helping the machinery requirements on different occasions. Motor of 50 kW and above rating draws very large current when started direct-on-line (DOL) affecting supply voltage dips which can adversely impact other equipment connected to the power grid. Sustained of large current through the motor during starting can caucuses climb temperature rise resulting in damage of the insulation of the motor windings. Therefore, the starting control of the motor needs to be operated thereby limiting its starting current. The conventional reduced voltage starting methods, such as star-delta starting and impedance starting, causes stepped variation of voltage whereas a soft-start derivative the voltage applied to the induction motor in a smooth Manner. A 3-phase reactor coil is normally employed as a soft-start. Time of soft start and stop is suitable. With this air core reactor coil soft starter voltage can be flexible to different loads. Provide motor with smooth and gradual starting current as per loads conditions

Keywords: HSFR (Harmonics free series reactor) motor starter, Air core coil, Torque Without Harmonics & losses