20-09-2014, 04:23 PM
Abstracts: An induction motor is the most modest electrical machine from constructional point of view, in the majority of the cases. Induction machines are by far the most common type of motor used in industrial, commercial or residential settings. Typical induction motors draw about 3 times the full load current while starting. The issue is this current exceeds the continuous ratings of the wire in the windings, so if the motor takes more than a few seconds to get up to operating speed the windings can be burned. So that to prevent this problem induction motor needed starter. Most induction motors are started directly on line, but when very large motors are started that way, they cause a disturbance of voltage on the supply lines due to large starting current surges. So the Star/Delta starters are probably the most common reduced voltage starters. This is starting method that reduces the starting current and starting torque. Star Delta Starter received starting current is about 30% of the starting current during DOL starter and starting torque is reduced to about 25% of the torque available at DOL starter. They are used in an attempt to reduce the start current applied to the motor during start as a means of reducing the disturbances and interference on the electrical supply.