Wireless power transmission and Motor choice

Power Transmission choices and explanation

As referenced in a previous post we need a way to wirelessly transfer power from the static part to the rotating part of our system. We found a 200W dev kit from Würth Elektronik but it seemed over-powered for our needs. Another integrated solution exists but is only good for 60W. Therefore we needed to estimate how much power our rotating system would need.

The bulk of our needs is in the LEDs. Considering 1280 LEDs and a multiplexing factor of 1:4, we would consume at most the power of 320 LEDs at a time. According to the specifications, an LED could use 60mA@3.3V at most. This gives us a max power consumption of 63W just for the LEDs. Even though this is a worst case scenario, it seemed to us that using a 60W power supply would be too risky, even more with all of the other components (SoM, wifi module etc..) and taking into account a DC-DC converter efficiency of 95%.

Since we couldn’t find another solution for wireless power transmission between 60W and 200W, we stuck with the 200W option, a using only coils and making our on driving circuitry would require us to be experts in induction power transmission and power supply design.

Motor and ESC choice

Our search for a BLDC motor took us all over the e-bike, drone and RC car and boat world. At first, we found a motor at Alien Power Systems but couldn’t find an ESC to match so they directed us towards Maytech. They make both ESCs and BLDC motors. We need a motor with enough torque to start the rotation considering our system will be quite heavy compared to an RC car or a drone propeller.

Getting both the motor and ESC from the same brand made it so we didn’t have to solder connectors or bother with pinout issues. It would allow us to have better support down the line should we have a technical issue. We then chose a Maytech MTVESC50A for our ESC which gives plenty of power for the Maytech 5055 1100W 70KV motor.

2 Replies to “Wireless power transmission and Motor choice”

  1. Could you explain how you’ll combine the motor and the power transmission?

    Looking at https://rose.telecom-paristech.fr/2020/11/21/choosing-a-shape, you don’t want anything on the side/the top (which is nice for sure), but then, that means that the coil can’t be on the motor axis, I think?

    It’s possible to put the coil out of the center, but then it will receive only a fraction of the power, so the computations wouldn’t hold.

    I’m guessing my assumption is wrong, and you’re planning on sharing coil and motor axis, but if so, could you explain how?

    1. Because of several constraints in the dev kit from Würth and the lack of other offerings in that segment, we’ve decided to move away from induction. We’ll be using the ball bearings for power and ground transmission. If we choose the bearing carefully and use a redundant bearing for each, we’ll have all the power and stability we need. There will be a blog post when the final choices and design models are made. I’m working on a 3d model of LitSpin and I plan on showing how power will be transmitted in that model so stay tuned.

Leave a Reply

Your email address will not be published. Required fields are marked *