What is the standard practice for reversing a three-phase motor?

Reversing a three-phase motor requires changing the phase sequence of the motor windings. This is accomplished by swapping any two of the three power leads connected to the motor. By doing so, the direction of the magnetic field generated within the motor is altered, which in turn changes the rotational direction of the motor shaft.

Switching L1 with L3 accomplishes this task, as it effectively alters the phase relationship between the three power leads. Since there are multiple ways to switch leads (as seen in the other options), what's crucial to remember is that any two leads can be swapped to reverse the motor direction. Therefore, switching L1 and L3 achieves the goal effectively and is a standard method.

Understanding this practice is important for those working with three-phase systems, as reversing motor direction is a common requirement in applications ranging from industrial machinery to HVAC systems. Other combinations, such as switching L2 and L3 or any other pairs, are also valid but the focus here was on switching L1 and L3 as a recognized standard practice.