The delta connection is found on motors above 5 horsepower. Larger ninelead motors may have multiple deltas, connected internally. The external lead numbers are the same, and they are connected as described in Fig. 5.26.
Both delta- and wye-connected motors combine the same lead numbers for high voltage. Each phase is connected series in both connections. As shown in Fig. 5.27, each phase is connected across the line.
Twelve-Lead Connection
The 12-lead connection gives a motor greater versatility. A motor with this connection can be used on four different voltages.
In Fig. 5.28, the end of each phase is accessible by leads T 10, T 11, and T 12. The rest of the leads (1 through 9) use the same lead number combinations as the nine-lead connection. Figures 5.29 through 5.32 show four different voltage connections that can be used on the 12-lead motor.
FIGURE 5.25 The delta connection connected for low voltage.
FIGURE 5.26 The multiple-delta connection is found in larger motors.
FIGURE 5.27 The delta connection connected for high voltage.
The lowest voltage connection is two delta (Fig. 5.29). The next-higher voltage connection is two wye (Fig. 5.30). (The two-delta voltage multiplied by the square root of 3 [1.73] equals the correct two-wye voltage.) The nexthigher voltage connection is one delta (Fig. 5.31). This voltage is twice the two-delta voltage.
The highest voltage is one wye (Fig. 5.32) (twice the two-wye voltage).
The voltage across each pole is the same on all four voltages.
The 12-lead connection can be connected part-winding start, using half-winding or two-thirds-winding start methods. The wye-start, delta-run, one-delta start, and two-wye run starting methods also work. (These start methods are discussed later under their separate headings.)
FIGURE 5.28 The 12-lead connection has the ends of each phase available for both wye and delta connections. The rest of the lead numbers are the same as those for a nine-lead wye or a delta connection.
FIGURE 5.29 Two delta is the lowest voltage connection for the 12-lead motor.
FIGURE 5.30 Voltage of the two-wye connection is 1.73 times that of the twodelta connection.
FIGURE 5.31 One-delta voltage is twice the value of two-delta voltage.
FIGURE 5.32 The highest voltage for the 12-lead connection is one Nye—twice that of the two-wye connection.