Originally Posted by Pdelcast
(Post 319114)
Well, let's start from the beginning.
The resistor array in the post was for a battery tester -- we don't use resistor arrays for testing ESCs. (We do use resistors for testing BECs -- and we also use resistors bank switching to test BECs under highly variable loads, but we don't use resistors for testing ESCs.)
When we do ESC testing, we have several options, and we test ESCs using all of these tests:
1. We have several testers that we call "Bucket test stations" where a large motor is submerged in light oil (in a metal five gallon bucket) with steel disks attached to the motor shaft. The steel disks rotating in the oil produce significant drag for testing at high constant loads.
2. We have what we call a "surge tester" where a motor is alternately loaded with a very heavy load and then a very light load. These load changes happen in a few milliseconds. The high loads are extremely high, and the low loads are near zero load. This test stresses the controller, and determines how well the controller handles rapid changes in motor load and RPM.
3. We have a Magtrol small motor dynonometer, which we use for efficiency testing, at varying loads.
4. And then of course, we test in target applications, with high rate dataloggers.
When we test ESCs, we have a choice on power sources -- most of our testing is done on a Sorensen 80-160 power supply (80V max, 160A max,) but when we need more current, we also have a Xantrex 20-400 (20V max, 400A max.) We also do testing with various Lipo cells and deep cycle Pb batteries.
When testing, the ESCs are placed in an airflow chamber, which simulates varying airflows. Usually we test with just a 5mph airflow -- but for some applications (like ducted fans) we may test with higher airflow. For some military and industrial applications, we test with 0 airflow.
Interesting that you mention the copper traces -- that's really one of our strong points. Our circuit boards are fabricated from 6 to 8 oz copper, and power boards often have 6 or 8 layers, sometimes with copper filled vias (depending on the application.) Our circuit boards often have 8 -10 times as much copper as other boards in the industry. The Mamba Max Pro, for example, is fabricated with an 8 layer board that has 6 oz copper on each layer. (6oz copper is 6 to 12 times as much copper as a typical circuit board.) The vias on the Mamba Max Pro have plating of a minimum of 2 mils of copper in-the-hole and a typical of 3 mils in-the-hole. And there are multiple dedicated planes for every phase. This makes for a very expensive circuit board -- but the losses in the circuit board are minimized, which allows us to handle significantly more power per square inch than our competitors. (And then, of course, we do all the circuit board assembly in-house -- which gives us tight control of quality...)
We also work with our circuit board suppliers to develop new production capabilities to continue to increase the amount of copper in the circuit boards without compromising circuit design. One of the designs I'm working on now uses an 8 layer circuit board with 6 oz copper on each layer with copper filled blind vias (vias that don't go all the way through the board.) Our circuit board manufacturers work closely with us to develop methods of producing high quality circuit boards with extremely high current densities and good yields.
That said, we have found that on some of the high-end controllers (very high power controllers -- like the Phoenix-ICE-160HV) the copper in the circuit board has become the real limiting factor. So, on some newer controllers we are using both high copper content circuit boards AND adding copper bus bars to the board. The ICE series uses copper bus bars to minimize losses in the circuit board copper AND has heat sinks bonded directly to the bus bars.
Thanx for the question!
Patrick
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