Quote:
Originally Posted by J57ltr
OK, so that makes more sense to me, but according to your website there have always been current ratings for the RC car controllers. They have changed since I first started looking at the MMM.
The Sidewinder used to be rated at 100 amps, now it's rated "More than you can handle!"
http://www.castlecreations.com/products/sidewinder.html
The Mamba Max has been rated at 100 amps continuous and still is according to the website.
http://www.castlecreations.com/products/mamba_max.html
The Mamba Monster was rated at "More than you can handle", but now has a rating of 120 amps continuous*
*Full throttle continuous operation with cooling airflow
http://www.castlecreations.com/produ...a_monster.html
Before I bought a MM I ran a brushed motor and modified my Duratrax Streak (12V capable and 12 turn limit). I asked all the guys around here what kind of current draw I would have on different turn motors and no one knew; most would glaze over when I started ask any technical question regarding anything to do with power needed for a system. Well I started modifying the Streak to handle more power by adding a couple more fets and then I realized that the traces on the board were too small to handle more than about 10 amps, so I cut some copper sheet and added it to the power traces. I was running an 8 turn motor just bashing around in my Rustler. So I have always (at least the last 5 or so years I have been back into this hobby) looked at ratings like they were absolute maximums of the componets, like adding up the pulsed drain currents of all the fets in the system. It takes more than componets to make an ESC the traces have to handle the current,
It’s really hard to get good information in the RC industry. The only way I was able to get any information at all was to buy the Eagletree data logger even if it has a very slow sample rate to me it was better than nothing.
So, if I may ask how do you test your ESC’s? Is it a purely a resistive load or an inductive load, or combo, (I did see the resistor array in one of your posts)? Do you use a large motor with a brake to load it to certain amperage? Is it done at a set “RPM”, or varying (but with the same current load) since the impedance of real motor changes with speed?
Just very curious about this.
Thanks
Jeff |
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