Homeade Voltage clamp

[Halfcrazy]

I will try to explain my simple voltage clamp and how it operates. It requires 2 components a simple ice cube relay with a 12vdc coil and 120vac contacts and a 3 phase magnetic contactor rated for the max current the turbine is capable of that has a 120vac coil.

We start with a 12 volt dc signal from the Classic that is always there until the input voltage goes above a user set value. (I believe this mode will be something like PV Trigger. This feature is being done as we speak we currently use a voltage monitoring relay but it is not necessary with the Classic)

The 12vdc then feeds into the coil of a simple relay with a 12vdc coil and 120vac contacts.

Then we take 120vac from the inverter  fed panel and feed it through the NC contacts of the above relay and into the coil of a 3 phase definite purpose contactor sized accordingly for the turbine we are stopping.

We then take the 3 phase ac from the turbine in parallel with the rectifier and feed that into one side of the contactor and we run short jumpers on the other side to short the 3 terminals.

The theory of operation is that the Classic will always have 12 volts out holding the relay open. When in the open state the relay will not pass ac through because we used the NC contacts. As soon as the Classic sees an input voltage of the user set point it removes the 12vdc thus passing ac on to the 3 phase contactor shorting out the turbine and stopping it. The reason I prefer this way is simply so if something happens to the Classic be it a breaker tripped or what have you the turbine stops.

Care must be used with this simple clamp to make sure the turbine you have can:
A-Stop without damage to the turbine when shorted at high speeds.
B-Actually stop when shorted for example a Bergey XL1 will not stop when shorted and I would worry this would burn the stator out.

I believe one could calculate the correct value of resistors to use instead of a hard short and it would be a little more delicate on the turbine but our otherpower style turbines do not seem to mind being stopped like this. I also believe we could program the Classic to latch and unlatch semi fast to kind of bump the voltage down a little milder for turbines that can not be stopped like the XL1 boB and I have to discuss this further

Here is a link to the Diagram http://www.midnitesolar.com/pdfs/Ryans%20Clipper_Diagram_11-24-2010.pdf

Ryan

[keyturbocars]

Thanks for this info Ryan.  I've been wondering how I could set up a homemade Clipper to work along with a Classic on my wind turbine.  I've got a Windmax HY-2000 2kW 48V wind turbine that I've seen crank out over 3kW during wind gusts in the 30mph range. 

Your voltage clamp uses a 120vac contactor. 

Do you know if they make 3 pole contactors that can utilize 48vdc on the coils? 

I do not run an inverter normally (unless grid power is down).  I divert power to an auxillary hot water heater.  I am on-grid and I could get 120vac from the grid, but the thing that makes me nervous is that during very high winds, the grid power can go down.  Then again, maybe it would be fine as I think you said the contactor would be NC.

I do not like the idea of abruptly shorting the wind turbine in high winds speeds, because I am concerned that doing so could create a surge/spike that could burn out stator windings.  I had something like this happen in the past on a different 2kW wind turbine.  It happened during strong winds and I went to shut it down with a 3 pole switch that I set up to short out the turbine.  Upon flipping the switch, I had a runaway turbine that was out of control.  It melted down internally before it threw a blade - thank God!  It was ruined.  I do not want to experience that again!  So, I like your idea of dumping 3 phase output to resistors to slow the turbine.  In fact, my HY-2000 controller system came with a 3 phase dump load (resistor heater box) that I could use.   

Would the 12vdc signal from the Classic allow the contactor to release the "brake" and turn the turbine back on once the voltage dropped?

Would there be any way for the Classic to also attempt to brake the wind turbine if a certain RPM was exceeded? 

I know from the factory that my wind turbine is supposed to be safe up to 800RPM.  So, let's say I want to be safe and limite max RPM to around 700RPM.  Just wondering if there is a way I could do this with the Classic and a homemade voltage clamp.

Edward

[Halfcrazy]

You probably can find a contactor with a dc coil I would rather see that myself as it does not depend on the inverter/grid. You could experiment with resistors on the other side of the contactor to make it a soft stop device. The Classic wont limit based on rpms that is where our Clippers will come in.

[keyturbocars]

Ryan wrote: "I also believe we could program the Classic to latch and unlatch semi fast to kind of bump the voltage down a little milder for turbines that can not be stopped like the XL1"

Something like that sounds good.  If there was a solid state contactor, then the frequency of the latching/unlatching could probably be higher.  If there are no 3 pole solid state contactors available, then I wonder if 3 Solid State Relays could be set up.

I'm also thinking that I could get the RPM braking I want indirectly (based on the voltage).  Not only would the voltage set point be to protect the Classic,  but I suspect it could also be set at a level that would equate to a safe turbine RPM.  Since I don't have tail furling, my turbine is always facing into the wind.  As wind speed increase, turbine RPM increases, and voltage output increases.  It should all track fairly closely and predictably.  Based on the "Power vs RPM" and "Power vs Wind Speed", I wonder if I could set the RPM limit indirectly based on voltage level.  I am on-grid.  My system is set up so that my battery bank is normally fully charged and in float mode for emergency backup, and I divert excess power with a Coleman Air controller to a auxillary hot water heater.  So, system voltages (on the battery side) stay fairly constant.  Perhaps I could calculate a voltage that would correlate to turbine RPM and use that as my RPM limit brake.  Assuming that this would also fall below the safe voltage limit of the Classic I chose (150, 200, 250), then that voltage set point might be able to serve both to protect the Classic and also my wind turbine from excessive RPM's.  Not sure, and I'm "thinking out loud" here.

In case it is pertinent to the discussion, here are some pictures showing my wind turbine set up and how I divert excess power off the battery bank and heat hot water.

http://www.facebook.com/album.php?aid=31445&id=100000264867099&l=6c791ef013

Edward

[boB]

You probably can find a contactor with a dc coil I would rather see that myself as it does not depend on the inverter/grid. You could experiment with resistors on the other side of the contactor to make it a soft stop device. The Classic wont limit based on rpms that is where our Clippers will come in.

UNLESS....   Unless the turbine is free-running...   Then you could equate RPM to Voltage and just limit
on  Voltage =  RPM = Wind speed.  ( if you can get the date to correlate those 3 things)

boB

[keyturbocars]

That's what I was thinking Bob.  Based on the data on my turbine, I am wondering if I could come up with a voltage limit that would correlate to RPM.





The trick is trying to come up with a correlation of how voltage varies with RPM on this turbine.  I've asked the manufacturer about this data, but they might not have understood what I was asking.  Not sure if they would have ever tested the wind turbine without their controller attached which clamps voltage to a max of 60VDC (dump point on their controller).  They might not even have this data. 

Edward

[keyturbocars]

OK.  I'm still seriously considering the Classic for my wind turbine, but I am waiting for them to be released to the general public and see what other people think once more people have tried them with wind.  In the meanwhile, I'm still keeping the Classic open as a top option.  I have 3 other ideas as well which include 2 existing wind turbine controllers that I currently own.  My main motivation in using the Clipper would be to have a more reliable turbine.  In part, by running higher stator voltages (less heating and less chance of stator meltdown).  Secondarily, I'd like to benefit from more efficient power production with the MPPT.

Keeping my Classic option open, I've been searching around for a 48VDC coil contactor to use with Ryan's idea of a homemade "Clipper".  I got one on eBay for $10 + around $20 shipping.  AMP ratings seem to be fine with 65A intermittent and 45A continuous.  Once the contactor connects, the current should drop quickly as the shorted turbine slows to a near standstill, or if I slow it way down with heating resistor elements.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rt=nc&nma=true&item=260704354161&si=ca3brfW4OhtvEZcEpoP4OljY9Gk%253D&viewitem=

Ryan, does this look like a contactor that would work with your idea of a homemade voltage clamp?

Have you and Bob done any more work with the 12V Classic output that could be "pulsed" to control a relay that would control the contactor?

[keyturbocars]

Happy New Year!

I was thinking about Ryan's homemade "Clipper" (voltage clamp).  Found these 3 phase Crydom Solid State contactors and the specs look good for possible Classic use.  They offer DC control versions with power handling capability of 50A per leg (Crydom P/N D53TP50DP).  



Looks like control power could come directly from the Clipper's aux relay output.  Crydom spec sheet lists control voltage of 3-32VDC and control current rated at a measley 10mA @ 5VDC.  So, it appears that the Clipper could easily control this directly, with no need for an intermediate relay.  Since it's solid state, then perhaps the Clipper could use a higher frequency pulse to apply "softer" braking to the turbine.  I found pricing on these at $99 online, so they are not unreasonably priced.  A heat sink would also be needed, but that would be simple and relatively inexpensive to come up with as well.

Here are the full specs on these Crydom 3 phase SSRs.

http://www.crydom.com/en/Products/Catalog/5_3tp.pdf

Looks like these might be a good match for the Classic.

Edward

[boB]

Happy New Year!

I was thinking about Ryan's homemade "Clipper" (voltage clamp).  Found these 3 phase Crydom Solid State contactors and the specs look good for possible Classic use.  They offer DC control versions with power handling capability of 50A per leg (Crydom P/N D53TP50DP).  



Looks like control power could come directly from the Clipper's aux relay output.  Crydom spec sheet lists control voltage of 3-32VDC and control current rated at a measley 10mA @ 5VDC.  So, it appears that the Clipper could easily control this directly, with no need for an intermediate relay.  Since it's solid state, then perhaps the Clipper could use a higher frequency pulse to apply "softer" braking to the turbine.  I found pricing on these at $99 online, so they are not unreasonably priced.  A heat sink would also be needed, but that would be simple and relatively inexpensive to come up with as well.

Here are the full specs on these Crydom 3 phase SSRs.

http://www.crydom.com/en/Products/Catalog/5_3tp.pdf

Looks like these might be a good match for the Classic.

Edward

Thanks Edward !     We will have to get one of these and check it out.

It might just work in a lot of situations !  Certainly worth a try.

boB

[keyturbocars]

boB, 

The specs look promising.  Hopefully, they pan out in real life.  I'm thinking of picking one up myself to have on hand for experimentation.  I already have an ABB 3 pole contactor with 48vdc coil that I picked up, but I'm not really excited about a mechanical relay.  I'm interested in doing something like Ryan showed with the Classic's aux relay output, but I like the idea of being able to "pulse" the brake with a SSR to get a "softer" braking effect.

At this point, I'm just not sure if 1 or 2 Classics would be required for my turbine.  I think Robin mentioned that there might be a Classic beta tester that has a Windmax HY-2000 turbine.  I'm looking forward to see how many Classics will be needed to handle this particular turbine.

Fun stuff!

Edward

[keyturbocars]

In case this will be of help to someone in the future, I'll add this to the thread...

For bigger turbines, I ran across some 3 phase solid state relays that can handle up to 90A per leg.  These are made by Powersem (German company) and they offer 25A, 50, 75A, & 90A versions.

http://www.powersem.net/range35.php

Not sure of all US dealers for Powersem, but they can be ordered here:

http://www.semimart.net/shop/index.php?cat=c43_Solid-State-Relays.html

The 90A per leg 3 phase SSR is not cheap at $200, but it can handle a lot of power.

Edward

[keyturbocars]

I'm also going to throw this thought out there in this thread.  I haven't yet tried the SSR relay, but I had something come to mind yesterday that got my attention.  One of the specs on these SSR relays finally sunk through my thick skull and brought up a question in my mind.  

The Crydom and Powersem 3 phase SSR's have the following voltage specs:

Crydom: 48-530Vrms
Powersem: 100-660Vrms

Now, the way that I plan to use the SSR, things might be OK.  I plan to use the 3 phase heating elements that came as the dump load for my HY-2000 wind turbine.  So, when the Classic energizes the aux relay output, the SSR would dump 3 phase wind turbine power to the heating elements.  

BUT, here's where I have a question....

For those that plan to utilize a crowbar type brake, when the SSR is triggered and the 3 phases are abruptly shorted out, then the voltage would drop to 0.  

Won't that cause the SSR to malfunction because it is relying on some Vrms in order to function properly???

That's the big question that comes to my mind.  There's a reason why they don't spec those SSR's with 0-XXX Vrms.  They must not function properly below that lower limit.  

In the case of dumping 3 phase power to a heating load, then if the wind turbine slows to the point that the voltage drops below the lower limit, then perhaps the SSR would also malfunction.  I'm not sure.  It's one of those things that would need to be tested in real life, I suppose.

Just throwing this out there as a possible monkey wrench to the SSR idea.  Of course, a standard 3 phase electromechanical relay/contactor should still work fine as Ryan has tested.  I already picked up one of those, but liked the SSR idea better, so that's why I went off investigating that route.  Perhaps the SSR idea still might work if the Classic applies "softer" braking, so the turbine doesn't slow to the point that the Vrms drops too low.  

Just food for thought.

Edward

[boB]

 It's one of those things that would need to be tested in real life, I suppose.

Edward

We will be buying a couple of these and trying them out, Edward.  Hopefully very soon !

boB

[Halfcrazy]

I suspect these relays like any other would have a coil voltage to activate them which would be a 12 vdc source from the Classic the 3 phase ac should not have any bearing on that. Just looked at them and they do have a coil to activate them so this would be a non issue as long as you can get the coil in 12vdc.

[mike90045]

Not sure how these work beyond 60hz or so, or if AC-DC rectification has been done previously, and these will be switching DC instead of 3 or more phase wild AC.