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.

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The new Power Supply and DC Load.

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App screenshot showing us pulling 83A

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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.