Answer Posted / sunil guru
there are various soft starters for both AC and DC machines...
for DC motor>>>>>
1.three point starter
2.four point starter
for AC motor>>>>>
1.star -delta starter.
2.auto transformer starter
3.rotor resistance starter
4.direct on line starter
soft starters are used>>>>>>
to reduce the starting current
to reduce the starting voltage
simultaneously to increase the torque of motor as it gains speed
soft starters are not only used to give a soft start to the motor but also 2 give protections like >>>>>>>>
1.in the absence of the starter the starting current will be too high so it would effect the parallel loads connected and may blow out the fuse
2.if the motor fails to start due to cogging then the circulating current may burn the armature winding of motor
3.as at start the starting current is 10-15 times high so starting torque also 10-15 times high so that torque may damage the motor getting if higher speed than rated.
so the soft starter's are used to start the motor in a safe way
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