There are two sources of potential excess voltage:

  1. Over-voltage coming from the power supply
  2. Over-voltage generated by an over-driven motor

Power Supply

The utilizes an SMBJ30A “clamp down” chip on the power input to detect any voltage coming in that is greater than 33.3V. If this is detected, it shorts the +24V to GND to protect the remaining electronics on the module. This chip serves a dual function as it also helps filter ESD voltage spikes as well.

Over-Driven Motor

The firmware monitors the motor voltage and if it rises above 30V, it automatically shunts the motor driver transistors together (the same as in normal braking) so that the energy is contained within the motor coils and away from the controller electronics. The inherent nature of motor coil geometry and construction allow for this driven state to be tolerated for several seconds or even minutes before there is any potential damage to the motor coil circuit. When the voltage drops below 29V, the firmware allows the motor power transistors to switch back to their normal operation.