What is the minimum speed that must be reached before the dynamic brake becomes effective?

The dynamic brake system is designed to provide effective braking by converting the energy from the train's motion into electrical energy, which is then dissipated as heat. For the dynamic brake to function properly, a certain minimum speed must be achieved. This is because dynamic braking relies on the motion of the train to generate the necessary electrical current through the traction motors, which then act as generators.

In this context, 15 MPH is the minimum speed required before the dynamic brake can effectively engage and provide sufficient braking force. Below this speed, the system doesn't generate enough electrical energy to create effective braking, making it less efficient or entirely ineffective at lower speeds. This threshold ensures that the dynamic brake operates correctly, optimizing its performance in helping to slow down the train safely.