I need to make a brake, interested in component suggestions

[makenzie71]

I have an inverter that works great until the turbine gets up to around 95v.  I need to build a brake that will kick on at 75vdc.  My normal A30 controllers can't handle that high of voltage and I've had terrible luck picking relays that don't burn up (yes I run them with sinks and fans).  I'd appreciate some suggestions for components (with links if you have them).  I need:

1.  Voltage switch that can handle 100+ volts.

2.  Relay that can handle 100+ volts and 50 amps.

3.  A resistor...turbine is a 48v/2000w turbine but I've seen it breeze right past that.  I need something that will be adequate to choke it down when voltage starts going nuts.

Your thoughts would be appreciated!

[joestue]

put the resistor on the ac side of the rectifier and use cheap ac SSR's

i built a SSR voltage clamp that triggers at around 220vac, sends current through a 10ohm 240v furnace heating element.

i placed a full wave rectifier on the 208 volts line to neutral from a 240vac rotary phase converter, followed by a 150 ohm resistor and a string of ~300 volts dc worth of 1 watt 24v zener diodes, directly into a SSR (which  is protected with its own zener, and a 10uf capacitor keeps the SSR on for just one line cycle and not one more)

when my friend's milling machine sends 70 amps back up the line during spindle stop, the 208 volts from the rpc increases to 250 volts and there is at least 25 amps rms flowing through the resistor, a little in excess of the 25amp SSR i bought. without the circuit the spindle drive will shut off due to overvoltage.

it has held up for thousands of cycles for a year now.

my first attempt burned up, used half watt zeners and a 68 ohm resistor. zeners got warm and failed shorted

[mbouwer]

What do you think of blade adjustment?

[Adriaan Kragten]

On my website: www.kdwindturbines.nl you find at the bottom of the menu KD reports, the manual of a 200 W, 27.6 V battery charge controller. You can put two or three 200 W dump loads in series to get a 400 W or 600 W device. If you put three dump loads in series, the nominal voltage becomes 82.8 V but the voltage of each voltage controller can be adjusted to a lower voltage which is accepted by your inverter. Now the total power which can be dissipated is 1200 W or 1800 W. But making of such a device is a lot of work and the dump loads must be electrically isolated from each other. A problem with one device for a much higher voltage is that the transitors don't survive this higher voltage. It might be possible to use only two dump loads in series and to increase the voltage of the voltage controller of one dump load up to 35 V. This may requier another value of the resistors on the dump load.