Why should the switching position of the master controller not be used as a running position long-term?

Using the switching position of the master controller as a long-term running position can lead to the burnout of starting resistors. This occurs because starting resistors are designed to handle high currents only for short durations during the initial phase of the train's operation when the motors are starting up. If the master controller remains in this position for an extended period, it forces the resistors to manage a load they are not meant to sustain continuously, leading to excessive heat generation and eventual failure of the resistors.

This understanding emphasizes the importance of utilizing the correct operational settings for the master controller to ensure the longevity of equipment and effective train operation. Properly transitioning to the appropriate running position is essential for maintaining the efficient function of the train's electrical and mechanical systems.