A possible reason that you had students thinking it was three circuits is that the power expander module has an additional PTC in it for the motors connected to it, so it basically functions as a third breaker in a robot using the expander. I coach my teams to break up the load across all three to reduce motor dropouts.
Wait, so is it recommended to put the Y-Cables on the CORTEX instead of on the expander(Like put one on 1-5 and the other on 6-10)? And I already heard this before, but I didn’t know if the expander had one or two.
Power Expander has one PTC device. You can use Y cables effectively on the Cortex to motors, on the Power Expander to motors, on the Cortex to Power Expander ports, or even on a Power expander port (out) to Power Expander port input. You do that last one to increase “fan out” or the ability to drive more motors from a single port.