How do dynamic brakes function on certain NYCTA cars?

Dynamic brakes operate by utilizing the electric traction motors of a train to create a braking force when the train needs to slow down. In the case of certain NYCTA cars, when the dynamic brake is engaged, the driving motors switch roles from providing propulsion to acting as generators.

This process involves the kinetic energy generated by the train's motion being converted into electrical energy, which is then dissipated as heat within the braking resistors or returned to the electrical system, if possible. The result is a significant reduction in speed without relying on mechanical systems such as friction pads. This method allows for smoother deceleration and reduces wear and tear on mechanical brake components, contributing to overall efficiency and performance of the train.