Homebrewed Electricity > Wind
alternators: does power potential need to be designed to match the intended load
brandnewb:
I am building an DIY low rpm 3 phase alternator for a DIY VAWT.
Already it shows that the open circuit voltage can reach 150V at 60 rpm.
Once some more upgrades have been realized that voltage will most likely be far higher, maybe even doubled. But wheter that is the case or not is not really relevant to my conundrum.
Now comes the tricky bit.
I have a wind charge controller that starts relaying power to the load (in this case a 48V LifePo4 battery array consisting of 16 cells in series) at 54V and hits the brakes by shorting all 3 phases at 60V
I have a comment earlier on one of my other threads that the battery array will keep the voltage rather constant and that it is the amperage that will increase once wind speed is picking up.
I am hoping soooooo much for that to be correct.
Or is it as other sources suggest that the supplied voltage to the load will be what ever the alternator is putting out?
Increasing design complexity of the alternator and also decreasing the overall usefulness of wind power related setups in general.
bigrockcandymountain:
It depends on the relative size of the battery and the turbine.
If the battery is oversized compared to the turbine, it will win and the voltage will stay at the battery voltage until it is fully charged.
If the generator is way oversized, it can cause the voltage to rise fairly quickly even when the batteries are not close to full.
You also need to make sure your generator windings are good for the amount of amps you will be making. If the wire is too small, you'll likely burn up the generator.
brandnewb:
The battery array has a size of about let say 1 8th of a cubic meter. The turbine is rather large. 4m, diam 5m height.
bigrockcandymountain:
Ok, so the thing to do some research on is the "C" rate of batteries.
Lead acid likes about a maximum C5 rate for charging. That means dead to full in 5 hours.
So my 428ah 48v bank can be charged at 85.6a or 4108 watts maximum.
Lithium might handle higher than that or it might not. Probably not without active cooling.
If you know the amp hour rating or kwh storage capacity of your battery, you can calculate the max charge rate pretty easy. I'm not familiar enough with lithium to guess based on physical size.
SparWeb:
--- Quote from: brandnewb on October 14, 2022, 05:39:10 AM ---
Already it shows that the open circuit voltage can reach 150V at 60 rpm.
--- End quote ---
Good so far. Simple math: with 150V open circuit at 60 rpm, then it will "cut-in" to a 54V battery at about 20 rpm. This is suitable for a big VAWT.
--- Quote from: brandnewb on October 14, 2022, 05:39:10 AM ---
I have a comment earlier on one of my other threads that the battery array will keep the voltage rather constant and that it is the amperage that will increase once wind speed is picking up.
--- End quote ---
Also good. It will work that way as long as the battery isn't undersized, as BRCM pointed out.
Read the stickers / stencils on the LiPO batteries and find the amp-hour capacity. Since they're in series the amp-hours for the string is the same for each cell.
Navigation
[0] Message Index
[#] Next page
Go to full version