Overvoltage protection for wind turbine output

An excellent dumpload would be 2 x 240v hot water elements in series, 1Kw each.

Also free hot water.

When you draw this amount of current, your voltage will fall significantly due to the internal resistance of the alternator.

The rectifier should have been rated to handle any current the alternator is capable of making, so any load connected should not be an issue.

If you live in an area where overly strong winds occur frequently, it may be better to get a turbine that is self speed limiting such as a yaw mount or blade pitch change as opposed to a braking device, otherwise you may burn out the alternator. All that energy must go somewhere. A double in windspeed will cube the power output so it may be best to restrict turbine speed.

Good luck.

The suggested practice put forth in the Inverter manual is to have the OV protection unit before the inverter. the idea is to disconnect the inverter and connect a load or short circuit, thereby taking the generator off grid- as such, water heaters won't work.

The manual specifically reccomends against mechanical methods of self speed limiting as you suggested.

I am thinking of using a voltage transducer with a setpoint activated dry contact and a switchover contactor. All I have to figure out is whether short circuiting the generator output is really a good idea or what resistors (resistance value and power capability) to use as a dumpload.

There was a post on cr4 a few days ago with almst the same switching problem. 600v/ 16A

regarding isolating a solar power feed, sorry dont have time to search maybe another can find

How about installing an over speed cut out to feather the prop. Would that not be easier. Many windmils have high speed cut outs that disengage the prop in high winds.

How would I do that? I am an electrical engineer, the mechanical guys get all hot and bothered when I play with their toys

Well some have springs or levers on the prop blades that engage a brake when the wind blows so hard it bends the leading edge of the prop backwards.

Then others will have a small clutch / pressure plate assembly that will disengage drive shaft from the prop and the generator.

The brakes I have seen a lot even a brake lock that stops the mill for maintance.

I believe I would want a brake because high winds would eventually rip the blades off the mill. But then you will know the winds in your area better that me.

I thought most wind turbines, well maybe the lower power versions, used a shunt regulator on the generator output?

The shunt regulator is much more efficient when the generator is below or at maximum output. If the generator goes above maximum voltage then the shunt regulator bypasses the extra power and acts as a brake for the generator.

Above a certain power though the pitch of the prop has to be altered to prevent damage - As a post above says the prop should be 'feathered' to prevent damage.

John.

we are building our own "improved" wind turbine; a vertical one.

the wind turbine will be equipped with what I equip it. Your shunt regulator is probably one of the two methods I mentioned in my question, for which I am searching for some guidlines.

otherwise, it is "trial and error time at the wind farm".

backfeed a mechanical disc break

Sounds like you might need a dynamic braking resistor to handle most of your smaller surges. It would allow you to produce at maximum capacity without mechanical braking every time you exceed rating. Larger intermittent spikes in load due to excessively high winds could be handled by mechanical means. It seems like the turbine should have mechanical limits in its original design to prevent physical damage.

May I suggest a "Tail" that will cause the propeller to go side onto the wind and then either use a disc or electrical brake......old windmills had such a system to save them in high wind situations.....they even used a small propeller to provide the energy to turn the windmill to face or not to face into wind.....

Its a problem that few private designers seem to cater for.......and its needed, even if only for repairs....