Some of the advantages of the wye / delta starter is the reduction in line current with respect to torque available. Unlike reduced voltage methods where the current is reduced by 57.7% when torque is reduced by 1/3, the wye / delta starter current is reduced by 1/3 when torque is reduced by 1/3.
The drawbacks of the wye / delta starter is the fact that the motor must be specially wound to provide both ends of each winding. This adds cost to the motor. Also, the starting voltage is fixed at 57.7% of the line-to-line voltage. Also,three contactors must be used and two must be mechanically interlocked to prevent the possibility of a line to line short should the contacts malfunction.
