KISS Wind Generator Failure

Saturday, March 13, 2004

017-12.720 N
087-32.400 W

I just experienced a failure of my KISS wind generator of a nature that I've been worried about for quite some time. The KISS generator has a thermal breaker on each of the 3 outputs of the generator. These open when the generator is getting too hot by generating too much power. This sounds OK in principle, but the problem is that when the breakers open, the blades freewheel at a very high rate of speed. The power curves that KISS supplies shows the generator producing 18 A at 20 Kts and 25 A at 25 Kts. However, there's nothing in their literature which shows the maximum sustainable power output.

A switch, located between the generator wiring and the connections to the battery provides a method of feathering the generator by shorting the outputs to ground or each other. In winds of less than 25 kts this typically causes the blades to spin at a very slow rate of speed. However, once the thermal breakers have tripped, this switch does nothing. To me this is a serious design flaw. The system should feather itself instead of letting the blades freewheel.

I first noticed this on the trip from FL to Guatemala last summer. I had just installed it and was quite surprised when it wouldn't feather in a squall that blew through. I contacted the US KISS distributor about this, and their response was that I should take a boat hook and use it to pull the generator sideways into the wind via a string that goes from the tail of the generator to the support pole. Yeah, that's a great concept until you're at sea with the boat pitching all over the place and probably a lot of other things going wrong at the same time.

Today we've been at anchor at Lighthouse Reef in Belize with a cold front blowing through. The winds have been in the 15 to 25 kt range all day. This morning the breakers tripped twice when the winds gusted over 30 for brief periods of time. Each time I was able to grab the string and swing it around to feather it. This afternoon the winds have been in the 15-20 kt range and the breakers have tripped twice. We were only generating about 17 amps sustained when this happened. The second time I was pulling the generator around when the string got caught in a blade and yanked the boat hook into the tail, snapping it off. I suppose that this is a lot better than having the boat hook strike a spinning blade and potentially impale me, but I'm not happy at all.

While in general I am happy with the KISS generator's simplicity, I think that this is a serious design problem which poses a substantial safety risk. If you're thinking about getting one, consider this fact before buying.

-- Geoff Schultz
Log ID: 468