Remote AirBreeze shutdown. Best practices?

ryann

I've got two remote unmanned research installations with both solar and wind generation. In both cases the wind is a small AirBreeze unit (one 12V, one 24V). We just blew out our first board in a 70+ knot storm (I also have an anemometer at the site). I have the ability to automatically analyse wind speed and battery state to determine when the AirBreeze should be shut down, but I'm not sure of the best way to do it.

I thought to use a DPDT relay to short the leads, but I'm concerned that this could be a bad idea if there's a lot of current. I then was wondering about using a large inrush limiting NTC thermistor which would start at 5 ohms and go down as it absorbed power.

Another though was a two stage shutdown where a DPDT relay switches in a large high current resistor between positive and negative. A second time delay relay would do a dead short after a few seconds.

inetdog

Re: Remote AirBreeze shutdown. Best practices?

If you either think that the current will be too high for your relay contacts when starting with a dead short or that the mechanical strain on the generator will be too high with the sudden torque on the generator of a dead short, then the two stage timed shutdown with a power resistor as the first stage makes sense.
Be sure that the power resistor you use can tolerate the full current and voltage of the turbine for several times the delay time, just in case.
And you are aware that a dead short will not bring the turbine to a dead stop? The blades will still spin, although slowly, unless you also have a mechanical brake that kicks in to prevent the unit from turning once the speed has been reduced far enough.
(A quick analogy is that no parachute, no matter how large, can cause you to hover in the air. It can only reduce your speed, since the drag force is proportional to your speed through the air.)