Wednesday, 21 December 2011

What are Soft starters?

Soft starters make are ABB, Siemens,power boss etc. Soft starters used to minimise the starting time of a motor and limit the current also. In starting time aalso we limit the input voltage of the motor. (Ramp Up Ramp Down Pedestal Step Down Supply Frequency Current Limit Time Current Limit Level Kick Start Time Kick Start Level Arc-less Switching)All theses parameters also we adjustable in soft starters.

Soft starters nothing but thyristor control starters,this different form VFD drives,All VFD drives are soft starters but All soft starters are not Drives,In VFD we can adjust the speed,Torque & master-slave operation,But in soft starters is used only to reduse starting current of motor and for soft starting of motors.

1)air cored reactor soft starters(hormonic effect free)
2)Iron core reactor soft starters(hormonic effect will be there)
2)flux compensating magnetic amplifier starters(FCMA)

Delta Primary & Star Secondary &
Delta Primary & Delta Secondary
This two arrangemetns are imposible....

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>>>>> -delta starter. transformer starter
3.rotor resistance starter 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 togive protections 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 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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