Independently rectified dc outputs connected in series

[mukunthko]

Hey guys

I have a windmill that i guess would produce about 20 watts peak power. I am planning to use 4 cycle dynamos 6 volt, 3 watt to generate electricity from this turbine. I have a DC-DC converter that needs an input in the range of 18-60 volts.

Hence I am planning to rectify these ac voltages from the 4 dynamos using seperate bridge rectifiers and connect the 4 rectified outputs in series to get a higher voltage.

Do any of you guys see any potential problems with this?

I know the voltages are going to be out of phase with respect to each other in a very random manner and that the rms voltage values with fluctate heavily as well.

But how exactly with this or any other problems be a concern to the rest of the system?

[Opera House]

Your outputs of each alternator will not be in phase so you will need to provide a 5,000 to 10,000 uF to filter each output so they can be added.   Each bridge will cause a 1-1.5V loss.

[Tom in NH]

This is the way I have my VAWT's 3 phases wired. It works quite well. I use full wave bridge rectifiers on each phase. The DC outputs are wired in series. This allows a higher voltage than the conventional star configuration.

I did have one itsy bitsy little problem, however, because I'm feeding the output to a homemade buck converter. The chips fry when input voltage exceeds 40 volts. If you are feeding directly into a battery, you should be ok, but if you feed into anything else, use care not to exceed any voltage limits.

I got around my problem by installing a couple relays. One flips the dc outputs between series and parallel depending on the voltage of one coil. The other shunts the output around the buck converter and straight into the battery if the output gets close to the limit.

The upshot is, separate full wave rectifiers can be wired in parallel OR series, no problem. --tom

[Flux]

Three phase is ok, the dc is nearly smooth. Cycle dynamos are single phase and you will need the capacitors to do much good. Treat it as a toy, the capacitors become monstrous   at higher power levels but cycle dynamos are toys anyway. Good learning for something practical.

Flux

[mukunthko]

Thanks a lot guys. That puts me on the lookout for a bunch of 10mF capacitors.

I was also wondering if I need any seperate blocking diodes between the battery and the dynamos to prevent the current from flowing backwards or if the diodes in the bridge rectifier would do the job?

Thanks

[Flux]

No need for blocking diodes, the bridges do that.

flux