SinusLeistungsSteller - SLS Development/2007 |
... subsequently the summary of 2007: 08.12.2007: ...again a few Amps more! With one power module (PM) with heatsink we successfully increased the current to 210Aac, without damaging the SLS. In order to generate high AC-currents, we mounted again the 40"x15" propeller. This way the airflow was a bit weaker and the motor heated up faster at lower RPM. Nevertheless 15 seconds were still possible at full power before the windings got more than 100°C. Applied for two power modules, this would be a SLS-60-420 !!! The whole test is shown below; with the 210A-peak in detail and the used SLS with additional heatsink (the SLS was only temporarily fixed with thermal paste and cable binder - OK, it could have been done better ...). ![]() ![]() ![]() 05.12.2007: Today we tested a SLS-60-200 with only one power module(!). As in the test of 16.11. (see below) we operated the SLS without heatsink on a copper-band motor with a 30x25 propeller - but with only one PM (in other words just with 12 MOSFETs). We knew that the temperature would increase significantly. More intersting however, was the question what current this configuration can survive ... At 130Aac we continued the test in "pulse-operation" and increased (step by step) the current by 5Aac. Everything was fine until 175Aac - but when we tried to increase up to 180Aac, a pair of MOSFETs "died". We need to find out the exact cause yet ... Anyway, it seems that, by the use of two power modules we can calculate on a SLS-60-300 ! ... and additional heatsinks remain also an option. ![]() 16.11.2007: The SLS-60-200 was able to reach his nominal current limit (Iac=200A). Simoltanously we were able to verify and confirm the calculated power of our copper-band motor: at 200Aac motor current, our voltage source supplied 9.300W - the low temperature increases of the SLS (<60°C) and motor (<95°C) assures that main power got to the propeller! A 30"x25" wooden propeller was used, which achieved 4.400rpm. The SLS-60-200 with two power modules without additional heatsinks was placed in the airflow and heated up only to 60°C (this is a result of further reduced switching losses). We are sure that we can achieve 300Aac and more with heatsinks! But first we need a suitable motor and a more powerful DC-source (our voltage source once more reached its limit). Because of that, we will work with only one module and try reaching 150Aac(+). This would mean 300Aac(+) with two power modules... The test, performed in current/torque control mode can be seen in the image below. We made breaks between the high current phases to cool the motor below 60°C. Before the last peak (arround minute 8) the voltage source limited (the limit was set to 170Adc), which is clearly visible at the voltage collapse. In the last startup the current limit was set to 200Adc - Now it got up to 200Aac or 9.300W (180Adc at 51,8V)... and all in controllable partial load! :-) ![]() 14.09.2007: Last week Mr. Süss reported about a special drive problem via phone. Today he visited us and the problem was solved :-) ... more here! ![]() 13.09.2007: For a long period of time we had to wait for the potted SLS with copper bars. Now it finally arrived! Inclusive the heavy copper bars with a 30mm² profile, both screwed high power capacitors and the two finger heatsinks it only weighs 596g (without heatsink just 510g). By this configuration a continous input power of 10KW should be possible! This matches a power-weight ratio of just 60g/KW. With slightly bigger heatsinks we can imagine a SLS with 60V and300A - first approaches in this direction we will perform shortly ... The copper bars are handmade - almost priceless ;-) and will not be available for purchase, only in exceptional cases. We promised to bring some colour into play: but the beautiful deep blue of the potting compound can not be seen, because of artificial light. ![]() ![]() ![]() ![]() 05.09.2007: The weeks before we had to work primarily on other projects - our "hobby" (the SLS) unfortunately had to wait and our homepage updates as well! Some of you already woundered why the news stopped. But all can calm down: By this month we have new ideas and are ready to further work on the SLS development! Of course we will report here about the results ... 06.07.2007: The first SLS-60-200 is shown in the picture below. First problems occured in mechanical stress in potted state during the temperature cycle test. We solved this problem by selecting the appropriate potting compound. As a potted version, the SLS weighs only 430g, including about 30cm of battery connection (2x4mm²) - this is 20g less than the aluminum case version! More important however is the fact that the modules are directly (for optimal cooling) in contact with the surrounding air and the electronic components itself are protected from outer influences. The cooling plates have a surface of 2 x (6x6)cm = 72cm² and are accessible for external heatsinks. The SLS with copper bars on the DC- and AC-side will also be available in a potted version. But for that, we need to customize the potting model a bit - no big deal. Also worth mentioning: the dark grey potting compound does not represent the final form in terms of colour and appearance. For the next tests we will bring some colour into play :-) ... ![]() ![]() ![]() 11.06.2007: The potting model arrived! In the next week we want to test and finish the first fully potted SLS. The aluminum case and shrinking tube version would than be unnecessary. By that, the power modules are from both sides directly accessible for external cooling (additional heatsinks in different sizes, fans or also water cooling). More soon ... Besides that, we reduced the occuring power loss remarkably by changing the mounting of the modules. In connection with a highly effective cooling concept, higher currents and powers are also possible. 25.04.2007: Dr. Werner Eck visited us together with his colleague Joachim Geiger. Mr. Eck developed and built a direct driven motor for a paraglider, which we tuned and matched on our SLS-60-200 prototype in terms of power. For such usage, the SLS is equipped with high power caps as well as copper bars (30mm²). The potted version of the SLS is not available yet ... In order to protect the electronic from dust etc ... The SLS was being provided with with a yellow shrinking tube and heatsinks. For the measurement we went to the airfield in Hettstadt. We only worked on the ground with a voltage source (the first fly with SLS has to wait for now) but power-levels up to 10KW were achieved. We measured 180A at about 56V at the DC-input, that is about 150A(eff) in the motor phases - so the SLS has some "space" for more motor current! Unfortunately, the surrounding air was not enough for the SLS on Werners back to maintain this power-level continuously. Despite the bad placed SLS, 10KW were possible for over one minute. Mr. Eck's motor was really impressive! Full power is available at 2000rpm with a 1,5m propeller - without gear! We think that the 10kW of continuous power is possible - since Mr. Eck already builds a new (improved!) version of the motor ... ... thank you Werner! ![]() ![]() ![]() ![]() ![]() 10.04.2007: During eastern we tested the SLS-60-200 in Peter Schmalenbach´s beautiful Mustang (2,86m wingspan at 19kg take off weight) under real circumstances. First we limited the motor current to 145A(eff) - in stand at max. 6400rpm, this is about 160A battery current, as we determined before at the test bench. This current represented the limit of the used 14S3P LIPO-battery. So 8KW-peak were possible - Peter used them with obvious enjoyment ;-) ... thank you Peter! ![]() ![]() ![]() 03.04.2007: Our first exemplar of the new SLS-60-200 was measured for test purposes on the test-bench. With our copper band motor and 40"-propeller 200A(eff) motor current was possible for more than 20s without any problems - the SLS could have run longer, but the motor had to survive the test ;-). The difference in temperature rise we suppose in unequal airflow at both sides of the heatsinks; the SLS was most likely placed slightly diagonal in the airflow. ![]() ![]() 12.03.2007: The serial parts with the improved cooling concept of the power modules arrive by the end of March! Than the 60V-SLS will be available finally and 2. edition of the 42V-SLS will also have the new modules. We are curious, what power enhancements (higher peak currents or longer full load periods) can be done with this new modules. As the measurement from 08.01. (see below) shows, 240A(eff) continuous currents in the motor phase should be possible, from the perspective of the SLS... stop..........................................................................stop 09.02.2007: Here the first results of our measurements: A SLS-42-220 was measured together with a "XY_ESC" (block commutated) under the same conditions. By measuring reactive and effective power on the controller input (battery side) we can clearly show the differences. For the load we used a PREDATOR with a 32"-propeller on 37V for each operated controller; our power measurement device has measured all parameters under equal conditions. We recorded these values and converted them into meaningful graphs. The most important finding in advance: The SLS lies ahead in both, the total efficiency (controller+motor) and the power factor (ratio of active to apparent power)! ... all details regarding the measurement with lots of diagrams, discussions and results are found HERE. ![]() ![]() ![]() ![]() 02.02.2007: The wait time for the modules enables us to work further on the measuring technology: A new professional power measurement device was purchased and tested already in operation. With this device it is possible to measure very precisely (active-/reactive-/apparent-)power as well as voltages and currents (middle and effective values) with a sampling rate of 100kHz and a 16Bit resolution. A direct comparison with conventional Steller-technology is now possible! We will report ... 08.01.2007: Today a SLS-42-110 had to show, how the new cooling concept really is. With only one module (-110!), which has a small passive heatsink, we could now analyse how the SLS is cooled by the new concept. Althrough we put 20A more on the SLS by the end of the 10 min operation, the temperature of the module increased slightly over 60°C! If we compare now the trace from 06.12.2006 (see below) than the progress shows some seriuos improvements. At that time we measured with a PREDATOR - but the current has its losses ... if we convert this result to the bigger SLS with 2 modules, a problem apperas: our motor is again to small for the tests ... :-( ... after the 10 minutes the winding reached 105°C ... In the moment we only have 3 power modules with the new cooling concept as prototypes - more will be available - manufactured - in March. ![]() 02.01.2007: The copper band windings were fixed with resin and the stator built in afterwards in the motor housing. First tests at motor currents till 150A(eff) had a temperature increase to ca. 85°C. The 40"-propeller was set to a relatively high gradient and already at 2.300 rotations per minute very high motor currents originated. The measurement took place at a power niveau of about 4KW und 37V input. Calculated to a doubled RPM (at smaller gradient but the same motor current) the motor should be suited for 8KW permanent power :-) ... It seems, we have finally found a fitting motor for our (highpower-) tests of the new SLS! ![]() ![]() ![]() The SLS-internal datalogger monitored one of these test-runs (see below). The new concept for the SLS cooling shows a remarkable improvement, which can be seen on the temperature progress. With the old concept the SLS already reached similar temperature below 100A. The synchron course of both temperatures is now nearly ideal. the new year starts well ... |