New kit arrived and testing continues

December 2, 2013 in 8 Channel PDU by Joshua Oster-Morris

Greetings friends. More kit arrived courtesy of eBay. Today we introduced the lab to a 2500W DC power supply which was surplus from our friends at General Motors. This device finally allows me to push the Motobrain all the way to 125A. I only intend to push the Motobrain to 100A so this is the last laboratory power supply I will need for this project. This is a great supplement to that DC load which we surplussed from NASA a few weeks back. Between the two we can now source and sink all the power we require of Motobrain. This afternoon I ran Motobrain for an hour pulling ≈80A through it. Nothing caught on fire which is a bonus! I found that Motobrain’s temperature rise accelerates as the current increases linearly. I expected this and I intend to further characterize it but the temps I saw today are not problematic yet. I have a new Power PCB with screw down terminals in fabrication now and I expect they will provide greater thermal mass and better heat dissipation. There is also room on the new board for a heat sink if deemed necessary.

After about 20 minutes at 80A the temperature settled in at about 80C. The hottest things I found on the Motobrain were the power MOSFETs as expected. I believe the correlation between current in Amperes and temperature in degrees Celsius is purely coincidental.


The new Power Supply and DC Load.


App screenshot showing us pulling 83A


The hottest thing I could find was a MOSFET. Here is was 76.6C though it got up to about 78C eventually.

FLIR0021[1]This is the of the whole lab bench in infrared. The Motobrain is bottom left. The current carrying wires are the glowing spaghetti you see all over.