Dave, I think you we are both in agreement with the initial post of Ed's thermal analysis, http://www.mail-archive.com/vortex-l%40eskimo.com/msg80803.html but it does not mention the difference between the destructive test in open air and the unit in normal operation which is constantly bathed in a heat extracting fluid.. are you modeling this in your SPICE calculation? The thermal circuit in the destructive test only has air cooling to keep the runaway at bay and represents a softer - more fragile target for the waveforms to temporarily exceed while I think the reactor in heavy heat sinking mode would have much higher tolerance for controlled PWM excursions into areas that would be considered runaway if not for the steady drain.
Fran [Vo]: ECAT Drive PWM Issues <http://www.mail-archive.com/[email protected]&q=subject:%22%5BVo %5D%3A+ECAT+Drive+PWM+Issues%22> David Roberson <http://www.mail-archive.com/[email protected]&q=from:%22David+Ro berson%22> Fri, 24 May 2013 23:30:52 -0700 <http://www.mail-archive.com/[email protected]&q=date:20130524> I was adjusting my spice model of the ECAT when I decided to determine how important it is to keep the device operating within the normally unstable region at all times. Here I refer to the unstable region as that operation range where the ECAT would tend toward over heating unless under control. There is no end to the questions which keep arising as to how heat can be applied in the proper format to keep an unstable device operating under control when it is capable of putting out more heat than required to drive it. And, the ECAT tends to operate best when the COP is equal to 6 which clearly is within this mode. One day this will be accepted. For now, I want to mention that it is important to keep the ECAT operating near the ultimate thermal run away region. If the device temperature is allowed to drop too far before the drive returns then the COP degrades significantly. And, as is somewhat demonstrated by the waveforms shown in the recent report, the length of time that the temperature hesitates at its greatest level is determined by how close <http://www.mail-archive.com/[email protected]/msg80977.html> to that ultimate run away temperature the device operates. My test runs demonstrate that the ECAT needs to be operating at a maximum temperature near to its ultimate thermal run away point and that the variation in output temperature needs to be maintained low by timing of the PWM drive. Both of these requirements should be met if the ECAT is to deliver the desired COP of 6 and remain stable. My spice model offers good guidance even though it can only approximate a real device. Dave
