The nine-lead delta-connected motor consists of three single-phase windings. Each phase has identical turns, coils, and wire size. Each phase end is connected to the start of the next phase (Fig. 6.8).
FIGURE 6.5 Low-voltage-connected nine-lead »re-connected motor
FIGURE 6.6 High-voltage-connected nine-lead Mye-connected motor.
Each phase is separated into two equal circuits. The two circuits can be connected in series or parallel. The series connection is high voltage, and the parallel connection is low voltage. The high-voltage (series) connection will always be rated twice the low-voltage (parallel) rating.
FIGURE 6.7 Current flows through two phases from Ll to 12
FIGURE 6.8 Nine-lead delta-connected motor.
The connection schematic (Fig. 6.9) can be used as a guide for testing any nine-lead delta-connected motor. Identical length between numbers means the data are identical between them that is, Tl to T4 and to T9; T2 to T5 and to T7; and T3 to T6 and to T8. Identical circuits can be comparison-
FIGURE 6.9 Using the nine-lead delta schematic to test the motor’s circuits.
tested. Identical faults in each phase circuit (six circuits total) are possible, but extremely unlikely