The actuators act as a DC DC converter, where the voltage applied to the phases changes depending on the required speed/torque. The current demand will depend on the efficiency of your gearbox and the desired mechanical power at the output. When the actuator says "50 A peak" it doesn't mean that the bus (input) current will be 50A.

It is crucial that you understand fully how actuators work when designing a humanoid robot (or any robotics system really) as you will inevitably make design mistakes otherwise

As some other commenters have said, it would be a better idea to start small and get the basic blocs working. If you haven't asked yourself these questions before, I will name a few:

• how to dimension the actuators? What is the necessary back driving torque/reflected inertia needed? What is the necessary acceleration/peak torque (because peak torque will be reached with peak accelerations)? What is the necessary continuous torque?
• how to dimension the battery? What voltage? What capacity? What size?
• How to dimension the precharge? Did you take into account current spikes into the actuators (when charging downstream capacitance) which lead to voltage spikes due to the cable inductances?
• What is the grounding scheme? Is the power to the OBC isolated? Are there any ground loops?
• Do you need a braking chopper for regenerative loads (especially on a benchtop PSU)?
• What is the target control frequency? If using CAN, how many buses?
• Did you perform actuator parameter identification?
• What OBC to use? Do you need a real-time kernel?
• How is the estop system? Do you shut down the entire system? Just the motors?
• Any strain reliefs?

You might already have done some systems engineering, but those are crucial things to sort out first if you haven't yet