How many main-line contactor assemblies are employed in an across-the-line AC reversing motor control?

An across-the-line AC reversing motor control utilizes two main-line contactor assemblies to function properly. Each contactor assembly is responsible for controlling the power delivered to the motor in either direction, enabling the motor to reverse its rotation.

In this control scheme, one contactor controls the motor for one direction of rotation, while the other contactor is engaged to reverse the motor's direction. This setup allows for enhanced control over the motor's operation by ensuring that each contactor can independently control the flow of electricity to the motor, effectively allowing for forward and reverse functions with minimal complexity.

Other choices do not apply because a single contactor would not suffice for the functionality required (forward and reverse operation), while three or four contactors would unnecessarily complicate the circuit without providing any additional benefits for standard reversing operations. Thus, the use of two contactor assemblies is both efficient and effective for achieving the desired control in an across-the-line AC motor application.