DELTA CONNECTIONS
Three-phase motors are also connected in delta. The same standard numbering system is used for delta- connected motors. If a dual-voltage motor is to be connected in delta, there must be 12 leads instead of 9 leads brought out at the terminal box.
Figure 14–11 shows the schematic diagram of a motor connected for operation as a high-voltage delta. Notice that the stator windings for each phase have been connected in series for operation on high voltage. If the motor is to be connected for operation on a low voltage, the windings will be connected in parallel as shown in Figure 14–12. Figure 14–13 shows an equivalent parallel connection.
SPECIAL CONNECTIONS
Some three-phase motors designed for operation on voltages higher than 600 volts may have more than 9 or 12 leads brought out at the terminal box. A motor with 15 or 18 leads can be found in high-voltage installations. A 15-lead motor has 3 coils per phase instead of 2. Figure 14–14 shows the proper number sequence for a 15-lead motor. Notice the leads are numbered in the same spiral as a 9-lead motor.
