As shown in the illustration of an electrically operated watertight door controller, how is reversal of the direction of the DC motor rotation achieved? Illustration EL-0115
• Trace how polarity at the DC door motor terminals changes in the circuit. • Compare the function of the O (open) and C (close) contactors/coils shown near the motor. • Notice what the LSO and LSC limit switches do versus what actually reverses current through the motor.
• Look at the four contacts around the door motor. When one set pulls in versus the other, what happens to the direction of current through the motor? • Do the reset master switch, remote closing switch, or limit switches change polarity, or do they only enable/interrupt a circuit? • Which component(s) directly control whether the motor is in the "open" circuit or the "close" circuit?
• Verify which device actually routes L1 and L2 to opposite sides of the DC motor when changing direction. • Confirm that the limit switches (LSO/LSC) only stop travel at the end of stroke and do not themselves swap leads. • Identify which item in the choices corresponds to energizing the contactor that feeds the open or close circuit to the motor.
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