Hi all,
I currently have a Classic with 4kW of PV and I'm contemplating adding a wind turbine and to connect it directly to the battery bank, without any charge controller. Then plan to manually turn on dump loads on the AC side using some automation software that monitors battery bank and the classic. But since there's a good chance that the automation software won't always work when needed, I also want a backup dump load that's controlled by the Classic's aux relay. So is there a way to turn on the Aux relay if the battery bank's voltage is higher than what the classic is expecting? i.e. if the battery bank is above float voltage (due to the charge from the turbine), but the classic is in float mode, can I trigger the Aux to come on? Also since this will be a backup emergency setting, it doesn't have to be PWM just a simple on or off will be enough for me to control a fixed sized dump load.
EDIT:
To be clear about how I'd like to connect this up:
PV connected to the Midnite Classic as is.
Wind turbine connected directly to the battery bank.
Fixed size AC load connected to the inverter and switched on or off through the Aux relay in the classic.
You could use AUX1 on Float high to trigger an SSR to either shut down the turbine or place dump load resistors into the AC lines from the turbine.
When the batteries are in float then why bother letting the turbine spin just to have its power dumped?
dgd
Stephen,
what will happen if the wind is very strong BEFORE the classic gets to float... what will activate the dump load?
--vtMaps
Quote from: dgd on July 07, 2014, 07:02:25 AM
You could use AUX1 on Float high to trigger an SSR to either shut down the turbine or place dump load resistors into the AC lines from the turbine.
When the batteries are in float then why bother letting the turbine spin just to have its power dumped?
Aha! Didn't consider placing the dump loads directly in the AC lines from the turbine, that's a good idea. Also like the fact that the turbine will only be used when it's needed; it being a spinny mechanical thing that can break down so less runtime is better.
Will it be safe for the dump loads to suddenly spring into action while the turbine is spinning?
EDIT: do you have a schematic about how this would be wired? would it be 3 SSRs and 3 resistors?
Quote from: vtmaps on July 07, 2014, 02:52:05 PM
what will happen if the wind is very strong BEFORE the classic gets to float... what will activate the dump load?
Mmm, so you're saying that during absorb for example the turbine could be providing all the power needed while the classic tries desperately to maintain the absorb set point by reducing solar output to 0, but with a strong enough wind, it could be that the battery goes above absorb V just on wind power alone; before the classic reaches float and turns on the dump loads.
Guess I could mitigate this risk a bit by not getting too powerful a turbine relative to the battery. The batt is a 700Ah C5 traction job, and the turbine I have my eye on is rated at only 1kW at 10m/s and 1.5kW max. So even absorbing at 4% charge rate without any voltage limit is within the EQ charging specs of the battery. Not great, but not disastrous. In theory the clever software based dumping on the AC side should work 90% of the time and the classic's AUX relay should just be the backup plan.
Stephen,
Sorry for late reply but I'm having problems with posts timing out. Hopefully when Ryan gets back he can look at this. I will try a much shorter reply without circuit diagram.
I used a Crydom 3ph ac relay D53TP50D with three 1.2ohm 1000W wire wound resistors connected to the 3 AC lines from the turbine, to A1,B1,C1 and a shorting wire between A2,B2,C3. When AUX1 connected to relay control inputs goes high the relay effectively shorts the 3 turbine lines via the resistors. This load will slow the turbine or may even stop it if Rs are low value.
You can use this to stop the turbine by not using resistors but just using the relay to short together the turbine AC lines.
dgd
Quote from: dgd on July 07, 2014, 07:02:25 AM
You could use AUX1 on Float high to trigger an SSR to either shut down the turbine or place dump load resistors into the AC lines from the turbine.
When the batteries are in float then why bother letting the turbine spin just to have its power dumped?
dgd
Remember that turning off the load(s) is not equivalent to turning the turbine off. It is equivalent to letting it spin out of control until its own control mechanisms can (maybe) furl it or otherwise disable it. You cannot turn the wind off when you do not need it.
Quote from: inetdog on July 10, 2014, 06:25:08 PM
Remember that turning off the load(s) is not equivalent to turning the turbine off. It is equivalent to letting it spin out of control until its own control mechanisms can (maybe) furl it or otherwise disable it. You cannot turn the wind off when you do not need it.
Thats why using an SSR controller by AUX to short together the turbine's AC lines is a nice way of stopping the turbine. Just disconnecting the load (battery) without either a substitute load (dump load resistors) or halting the turbine could destroy or severely reduce the turbine's lifetime...
dgd