rectifiying

[jmk]

  I am building Hues 12' turbine. I converted it to 24 volts. His plan calls for 40 amp recterfires. Would 35 volt rectifiers work? I not sure how to read the diogram? Tre phase. One out wire to each rectifier? Sory all brand new to me.Including the cumputer. So this has been a big prodgject!   Brake swith inbetween?    

[terry5732]

If your watts are same then 20 would suffice so 35 would be great.

[Nando]

No, 35 Volts will not do.

The Reverse breakdown voltage of a rectifier is based on: the output voltage and the source voltage

If you have 24 Volts out for a battery ( it should be 29 volts), the reverse breakdown would be 29 volts for the battery and 29 volts for the power source, in this case it should be 38 Volts --- but due to the behavior of the power source the voltage could go much higher -- so think that you need at least 100 Volts reverse breakdown.

A good reasoning is to use, for low voltages, 4 times the battery voltage.

For high voltage then an accurate calculation like for 400 Volts battery voltage the reverse breakdown may run around 1200 Volts.

All this may guarantee the life of the diodes under extreme conditions with some inductance in the circuit.

Regards

Nando

[mlz]

Er, Nando, you got your volts and amps crossed there, these are probably (just a guess) the 200 volt, 35 amp units that Dan sells.  Me personally I like to over engineer, and would put at least 2 in per phase (total of 6).  Also I would keep a few spare.  Even when everything looks good on paper, you find out your heat sink compound wasn't up to par, or your heat sink wasn't big enough.  It's rough waiting a few days for rectifiers to get to you when your out in the boonies...

[adelaide]

the break swich may be using hi amp relay or relays depending how many phases to short all outputs together befor it goes to the rectafiers. this works as eletronic break to slow right down in light and medium wind for me. but hi wind it may not work so furling is esenshal. i run a third thin wire up pole and put + up to trigger relay/s to short coils befor rectafiers (- is alredy up their for outher side relay)).because i like rectafiers in the wind/cooling

some alts may heat more with this idear but i use it on 5 of mine and never had prob. over kill usful in eletronics so at least use 3 bridj with both ac joined toghther on each phase (if 3 phase ) with good heatsink in airflow, the things vibrart alot so makes shore things cant rattle lose glue some nuts/screws on it if u can big fues by batt and spers good idear 2

[Nando]

Reading his message he used the 35 volts rectifier and I based my message on that remark.

Also, I did not know about who was selling what type of rectifiers and my message indicated the steps to determine the diode reverse volt breakdown-- also did not relate to the amperage.

Nando

[terry5732]

I assumed he meant 35 amp and not 35 volt as he said the plans called for 40 amp. Of course they must be rated for voltage higher than the voltage through them.

[terry5732]

I once thought it would help the diodes to run cooler to over rate or double etc. However the heat comes from the turn on voltage and by doubling you are just making more heat assuming you have the power to turn them both on - wasted energy. Your  best efficiency is with the least rated diodes that will work without burning. Tough call - efficiency or risk of failure.

[ghurd]

Don't mean to argue, but what changed your mind?

I have found the turn-on voltage considerably less than rated, when operated below the rated amps.

Therefore, less than rated amps is less than listed volts, less heat and dissapated watts, less waste, less chance of failure, and higher efficiency.

G-