Oz, I will program the power curve in the controller to let it run the turbine at 475 rpm @ 147 volts, or about TSR 6 @ 30 mph. The controller begins to unload the turbine from the DC load if one of two things happens:
- The amp limit you set in the controller is reached (I have this set at 84 amps presently).
- Either absorb or float stages of charging are reached.
When the controller unloads the turbine from the DC load due to one of the above the Aux 2 output of the controller switches the turbine over to the three-phase load with PWM driving a SSR. It regulates the voltage at the 147 volts. If it can't hold it at 147 due to excess turbine output (wind speed in excess of 30 mph) it will go over the controller's input voltage limit of 150 volts. The controller then goes into what is called "HyperVOC". In HyperVOC the controller stops charging batteries and the load is totally switched over to three-phase.
When the input voltage again drops below 150 the controller starts charging batteries again.
At 40 mph wind speed the turbine should not actually exceed 500 rpm, as the harder it tries to turn as the wind picks up, the load of the three-phase water heating increases faster than shaft power and stalls the rotor. I'm setting it up to furl between 35-40 mph with the rotor running on the bottom end of it's useful power curve (~ TSR 5).
If I would let it scream to 700 rpm by not having a heavy duty enough three-phase heating load, it would indeed be an interesting machine.
The first turbine taught me about how the controller works and I found you can't blow it up by running it over voltage or over amping it. boB and Robin have been in the business long enough to know better that to let that happen. This one is being designed to be able to take better advantage of the turbine's ability to heat water with high-voltage three-phase power, and the controller's ability to switch it back and forth and "blend" both the DC and AC loads as needed to control the turbine's speed.
Many times, what happens is that with both solar and wind the bank will reach float by noon and then the turbine is heating water all afternoon. The solar controllers regulate the bank at 26.5 volts and the bank and inverter loads can't even come close to using full turbine output. So rather than running the heater elements with inverter power like I do with my other turbines, why not heat water direct with the three-phase power off the turbine? You can heat a lot of damn water with 3 kW all afternoon - probably more than we can use in a day, and we got two 55 gallon water heaters to store it. That's why I'm doing this one this way.
I got one element controlled by the thermostat and that one runs off inverter power. That one insures that we always have at least 25 gallons of 125 degree water in the primary water heater. I got the other three elements (bottom in the primary heater and both in the pre-heater) wired delta for the clipper load.
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Chris