AS 1202.2-1976

Part 2 specifies requirements that are additional to those in Part 1, and apply to hand or automatically operated starters for industrial use, the main contacts of which are intended to be connected to circuits of rated voltage not exceeding 1000 volt a.c.

This Part of the specification applies to star-delta starters for industrial use, intended to start in the star connection, accelerate an a.c. three-phase motor to normal speed, provide means for the protection of the motor and its associated circuits against operating overloads, and cause the motor to stop intentionally.The star-delta starters dealt with in this Part are not intended for reversing motors rapidly and, therefore, utilization category AC-4 included in Part 1* does not appear. Moreover, they are not normally designed to interrupt short-circuit currents; therefore, suitable short-circuit protection should form part of the installation but not necessarily in the starter (see Appendix C of Part 1).This Part applies only to starters, the main contacts of which are intended to be connected to circuits the rated voltage of which does not exceed 1000 V a.c.The clauses of this Part relating to overload protection are not applicable to starters operating in conjunction with over-temperature protective devices built into the motors (see AS 1023, Part 1).NOTES:1. In the star connection, the current in the line and the torque of the motor are about one-third of the corresponding values for delta connection. Therefore, star-delta starters are used when the inrush current due to the starting is to be limited, or when the driven machine requires a limited torque for starting. Typical curves for starting current, of starting torque of the motor, and of torque of the driven machine are shown in Fig. F1.2. In order to avoid too large a peak of current or torque when changing the connection from star to delta, it is recommended that this changeover occur only when the motor has reached a speed higher than 80 percent of its rated speed (see Appendix F).

Under Revision See DR 94015