AX 300-3 & VLLR

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Joined: 10/02/2007
Location: Australia
Posts: 729
Posted: 11:25pm 22 May 2012      

I had a bit of wind about a week ago that tested the "VLLR" liquid resistor control system out a little and also gave a good indication on how quickly AXFX type stators heat up when they are starting to pump out the watts . I would not call it a high wind day but in a period of about 6 min the stator temp went from 70deg up to 80deg with a few gusts at around 35 ~ 40klm . The data log can be be seen below for that period with the shut down for ( high RPM ) coming in at the gust peak and at the same time the High Temp shutdown activated @ 80DegC. Prior to this there were a few peaks of 1500 ~ 1600W, this being well below what this mill has peaked at previously. The Restart can be seen as "Top Limit Reached " as the plates come out of the fluid.

As the whole day text file is too long to fit on a screen dump I can only show sections of it, but for most of the day the temp sat around the 50~60deg in 15 to 20km wind.

The pic below is a screen dump of the same period on the windmill data logging screen which shows the the peaks coming through for the same period on the VLLR status log file and being logged at 10sec intervals which does not capture the actual peaks, the shut down period and then re-start can be seen.

The gusts were definately not sustained , and what I find now with the ability to log what is going on with heat up at the mill head is a real eye opener . As the 80deg Temp set point shutdown has been a trial to see what it actually takes to get to that point and the fact that it really does not take high output for a long time to get to that point.

With cooked stators being one of the most common failures for axial flux type alternators it is little wonder when you see this data . With the heat build up over a prolonged high output period causing the softening of the resins used in the stator combined with the forces trying to bend and move the copper windings, then it can all to quickly add up to a burn out and/or a run away mill as I have experienced 2 times now with this mill when a forced shutdown was required on top of prolonged high wind and output.

All in all the Liquid Resistor Control system did its job in automaticly protecting the mill and smoothly stopping the mill when a set point was reached and held the blades in stall untill it was allowed to restart, the High temp set has now been raised to 95deg and the RPM left as is to see if that will keep the stator temp stable before raising the RPMs . I will also add that through all this the mill was still furling as it should in the gusts and even with the furling set quite soft the stator still heats up fairly quickly.

PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits