Classic Current Handling Capacity

[keyturbocars]

I'm still not 100% sure which of the 3 Classic models would be best for my wind turbine.  I've got a "2kW" wind turbine, but I've seen brief surges up to 3.5kW during strong wind gusts.  Most I've seen on the ammeter is 65A.  This is for a 48V battery system.  I would expect the Classic MPPT to boost the power curve even further, but I do not think it will get past 3.5kW very much.  I'd expect the Classic to fatten up the power curve at lower than peak power.

I would prefer to have the biggest voltage ceiling possible, but I don't think the Classic 250 would be able to handle the current of my wind turbine.  I am thinking that  Classic 200 might be better, but maybe I'd need the higher current capacity of the 150.  But, then I lose some of the higher voltage advantage of the Classic.

What do you Midnite folks recommend here?

Edward

[Halfcrazy]

I am leaning towards the 200 for most turbines as it gives you the balance between voltage to play with and current capability

[Robin]

It is difficult to tell which Classic is best suited for your turbine. It really comes down to free wheeling output voltage. If the turbine is going to exceed our HyperVOC voltage when the batteries are charged, then it is very possible that the Classic will turn into a gooey pile of mush. This condition is pretty hard to cover under warranty. There  are voltage limiters available fron DC-Power, but are at a fixed voltage that will work with the 150 Classic. Ryan's Clipper is adjustable and is a good plan for the time being. We are in development of two different voltage limiters (Clippers). They won't be ready for about 6 months though.
Choose your Classic based on what the output voltage is going to be. IT is extremely important to control the voltage coming into the Classic!

[keyturbocars]

OK.  Thanks for the feedback, Ryan and Robin.

Let's say I have a Classic 200 with a voltage clamp to make sure voltage into the Classic never exceeds Hyper VOC.  What would you say would be the highest current carrying capacity?  How many amps can the Classic 200 handle with a 48V system?

Edward

[Halfcrazy]

here you go

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[keyturbocars]

Thanks Ryan.  That's exactly what I wanted.

On that chart, the maximum PV input voltage on the Classic 200 is listed as 315V.  Is that a typo?  That's the same as the Classic 250.

Edward

[keyturbocars]

Looking at the Absolute Current Output, I see the following power handling capability:

Classic 150 (83a x 48v): 3984W
Classic 200 (65a x 48v): 3120W
Classic 250 (55a x 48v): 2640W

Can you explain why the power handling ability is so much less on the higher voltage Classics?

Could you also explain what will happen if the Absolute Current Output rating is exceeded? 

I remember boB or Robin saying that the Classic will continue to try to operate as long as temperatures are not too high.  I would have the Classic mounted in an air conditioned room and have it fully vented, so maybe I could get away with slightly higher currents.   

I keep thinking about how the Classic will work with my HY-2000 wind turbine.  It almost looks like I'd need to choose the Classic 150 (or 2 Classics 200's or 250's) to have the current carry capacity for this wind turbine.  Usually peak power during high winds is 60A.  I've seen 65A surges for a couple seconds before.  I think that's about the upper limit of what this turbine can produce while being clamped to the 48V battery bank.   I'd estimate that the Classic might boost peak power a little but probably no more than 25%. Even so, that would put peak power output right around 80A.  That means I'd need the Classic 150 to be able to handle that current.  Then, I think the voltage clamp necessary to protect the Classic might really kill the wind turbines power output.  This HY-2000 wind turbine makes peak power around 650 RPM.  Having to run with 2 Classics could get expensive.   Still trying to figure out if this is going to work with my wind turbine.

Edward

[Robin]

The Classic does have limited surge power available. Beta units had unlimited surge power and the results were spectacular. I do not know what boB has done to production units to reduce the unlimited surge capability. We do plan on keeping this feature in some form or another, but we also need to make sure it doesn't affect reliability. The Classic controlls the output voltage of the turbine. When output power reaches the max continuous point, the Classic has no choice but to allow the turbine output to increase. When the voltage increases higher than what is should be for maximum output power, the output power goes down. Depending on how hard the wind is blowing and how full the battery bank is, the voltage may rise to the maximum input voltage. On a Classic250, this would be 250 volts DC. The Classic will shut off when it reaches this voltage. The Classic will then be in Hyper VOC mode to protect against the impending higher voltage that is sure to come. Since the Classic is turned off, the turbine will free wheel. The output voltage of an unloaded turbine spinning fast is different for each turbine model. This condition is dangerous. Tod at Bergey designed the 48V XL.1 to run below 250 volts in this condition. We do not know where any other turbine will end up. This is why we are designing two different Clippers (voltage limiters). You can always use Ryan's trick to stack two Classics if power is going to be too great. We have lots to learn as customers hook up the different turbines available. Sometimes the results will not be a plesant experience since the Clipper is not yet available. That is not an excuse to just let her rip though. Replacing blown up Classics from over voltage is expensive. I'm sure we will make special cases at first since we are in uncharted territory, but keep in mind that an over voltage condition is very dangerous for the Classic. That said, we have had many over voltage events during our beta testing with only one melt down. There was nothing salvageable after that event with a 17 foot otherpower turbine. Two Classics solved the problem and it is now happy putting out 9000 watts.

[ibeweagle]

Robin thanks for the info on the other power 17 footer would have like to see halfcrazy beta unit melted puddel haha what about the use of stacked classics and one being set to (140volts) for aux relay say to a 3phase transformer dump load to water heater or second battery bank and the secound classic (148volts)  like ryans (halfcrazy)  crowbar relay will see first will take baby steps on set points and amps will get some more info and drawing when hooked up  also could reverse the set up for amps too have a happy new year !!!!!! cheers Mike

[Robin]

I will let Halfcrazy step in on the alternate dump loads, but I think I understand what you are suggesting. The dump loads don't do any good at all when connected to the output of the controller. That is how present day battery regulation is done. We need to stop the turbine from putting out too much voltage. This dump load must be connected to the turbine side of things. The Classic input must be isolated from the dump load by a rectifier or some similar gizmp. If you short out the input of the Classic(or any other controller0, it will go up in smoke. I do not know how to insert a picture here yet, but Ryan can show you a picture of his handy work with the melted down Classic. We really don't want to see this happening.

[ibeweagle]

thanks Robin for the info and yes will isolate the classic input with rectifiers have some good photos of stator burn outs but have not lost a magnet yet will get with Ryan before I thorough the switch and make drawing for it like his homemade diversion load relay pdf file Happy New year sub zero temps here in Rochester just board cabin feaver will be waiting for spring and getting to work on the new equipment cheers Mike

[Halfcrazy]

Ok did some one ask for a picture of one of my record setting smoke shows 



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[keyturbocars]

Thanks for the picture Ryan.  Now I can see what you meant when you replied to my other Classic Cooling post.  Loooks like the 8 MOSFETs heat sink on the die cast aluminum case along the right side.  There are ribs on the outside of the case and the "turbo" fan blow across those ribs/fins.  

Was that a Classic 150, 200, or 250?

That 17' turbine put out 9kW peak, didn't it? 

That's a LOT of power to run through one Classic!

- Edward

[keyturbocars]

I can understand that the current capacity of each of the Classic versions (150, 200, 250) is a function of the power that needs to be handled (and resulting heat dissapated).  So, the higher voltage capacity of the Classic 250 means that it can handle less current (P=IV). 

What my brain keeps coming back to is whether a Classic 250 that is run at a lower voltage limit would be able to handle more current than the specs show (Classic 250 = 58A max @ 48V)?

For example, lets say I buy a Classic 250 and then discover that my HY-2000 turbine runs at a voltage of 190V at peak power output.  If I use Ryan's homemade Clipper idea and maybe tweak the idea a little using a Crydom 3 phase SSR, and keep the voltage clamp set to 200V.  With the lower voltage, then I am assuming that the current capacity of the Classic would go up because the total power handled (and heat dissipated) would be less.

In that situation, would a Classic 250 have the current carrying capability of a Classic 200? 

I suspect not exactly, because of the different components on the board for the higher voltage capability.  But, I wonder if it would be close.  You might be seeing where my thinking is going with this.  Choose the higher voltage Classic since I am not sure of what the voltage will be on my particular turbine, and run it at a lower voltage level to get additional current capacity.

Edward

[Halfcrazy]

That is a tough one to explain fully. the higher voltage units do handle less current for a couple reasons as you stated. The true issue is the current limit setting from the factory obviously if we made the 250 say adjustable up to 90 amps people would hook up 90 amps of solar panels and cook it. Now the tricky part wind is usually not steady so say you where running a steady 35-40 amps but a quick gust hits it and it would like to spike to say 80 amps for a second or 2. I think we need to have some sort of surge capability above max amperage setting but only in wind mode? I have chatted with boB about this and it may be something he works out at some point. The Classic would run until it sensed it was getting warm than back its current limit down a touch. Like I said it is a slippery slope.