Using the schematic diagram in Figure 20–23, determine the number of control wires needed to control the three-phase motor. Use the terminal and wire identification shown in the schematic as well as proper power circuit identification.
FIG. 20–23
Calculate the number of control wires required to control the three-phase motor in Figure 20–23.
Explanation of Solution
The 3 wires are connected to the externally operated disconnect switch, and the switch is connected to pull box through 3 wires. Four wires are used to connect stations 1 and 2. Four wires and three wires are used to connect station 2 and station 3 to pull box, respectively. The pull box is connected to motor starter using 6 wires, and finally, starter is connected to a three-phase motor using 3 wires. Redraw the given figure with the representation of the required control wires as shown in Figure 1.
Conclusion:
Thus, the number of control wires required to control the three-phase motor in Figure 20-23 is calculated.
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Chapter 20 Solutions
Electric Motor Control
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