Wind-Box vs Homemade Rectifier

[Rob Littiken]

I'm trying to decide if there are any advantages to using the Aurora Wind Box or just building my own retifier and use the Omron relay for switching on a resistive load.

I know that Cor tried using the dump load switch on the Wind Box and had trouble, but his generator was putting out 200V under normal conditions and when it hit 530V it was way out of control. I'm winding my stator to put out about 450V on the top end, so when it hits 530V it wont be as far out of control and might control it better?

Is the crow bar worth having in the Wind-Box? Any thoughts on why Rob B has seen the box burn up when over voltage, rather than the crow bar to work correctly?

Any advatages to having the frequency output for MPH on the Wind-Box?

Is the Wind-Box any more effecient in converting to Vdc than the homemade rectifiers?

Thanks Rob B, Cor or anyone else who might have some input on this.

Rob L

[Ulf Hansén]

Hi

I have used a omron relay to brake down the gen at 400v. It works great ,I also put a time relay in series so I can adjust restart time .
Now I use 15 min and I probably going for longer time for restart

Regards
Ulf Hansén

[Rob Beckers]

Ulf, what do you use for the timer relay? I have an application that could benefit from something like that.

Rob, the reason the Power-One wind box self-destructs is due to a design error: They use a number of NTC resistors in parallel to discharge the capacitors. You can't put NTCs in parallel, one will always take the majority of the current, they don't 'share' well. So what happens is that they burn out when activated.

If it is for yourself, just make your own rectifier and overvoltage protection box. The Power-One wind box is great for commercial use, where the installer cannot come with a home-made solution. For a DIY wind turbine it is easy enough to build your own, and if you want a crowbar that is actually pretty easy to design as well (takes one SCR and a bunch of zener diodes, but make sure there's a DC fuse that can be blow by it, the whole AC concept that Power-One relies on doesn't work for that purpose). The Power-One box has lots of capacitors in it to smooth out the DC, in fact that's probably where most of the money is. It looks though that the Aurora inverters are very tolerant of ripple, many Chinese turbines have nothing more than a rectifier, some even just single-phase (3-phase produces much smoother DC compared to single-phase without capacitors). The inverter seems to handle that just fine. So, it seems the capacitors are not needed to make it work.

-RoB-

[Rob Littiken]

Sounds good Rob. I think building a rectifier and over voltage protection sounds like fun.

I think I'm following the the design for the crow bar, but any chance you could post a sketch and list any important part #'s

Thanks for all your help. I'm really enjoying designing and building this system,

Rob L

[Rob Beckers]

Hi Rob,

I've sent you some stuff by E-mail...

-RoB-

[Rob Littiken]

Thanks Rob B

[Ulf Hansén]

Ulf, what do you use for the timer relay? I have an application that could benefit from something like that.

Rob, the reason the Power-One wind box self-destructs is due to a design error: They use a number of NTC resistors in parallel to discharge the capacitors. You can't put NTCs in parallel, one will always take the majority of the current, they don't 'share' well. So what happens is that they burn out when activated.

If it is for yourself, just make your own rectifier and overvoltage protection box. The Power-One wind box is great for commercial use, where the installer cannot come with a home-made solution. For a DIY wind turbine it is easy enough to build your own, and if you want a crowbar that is actually pretty easy to design as well (takes one SCR and a bunch of zener diodes, but make sure there's a DC fuse that can be blow by it, the whole AC concept that Power-One relies on doesn't work for that purpose). The Power-One box has lots of capacitors in it to smooth out the DC, in fact that's probably where most of the money is. It looks though that the Aurora inverters are very tolerant of ripple, many Chinese turbines have nothing more than a rectifier, some even just single-phase (3-phase produces much smoother DC compared to single-phase without capacitors). The inverter seems to handle that just fine. So, it seems the capacitors are not needed to make it work.

-RoB-

Hi Im away working ,Sening a drawing when im back home
Ulf

[Martin Gray]

Hi Rob,

I've sent you some stuff by E-mail...

-RoB-
-RoB-, I was hoping you would post the rectifier+over voltage protection info here :(
I'm also very interested.
Martin.

[Rob Beckers]

More in general: The whole idea of using a crowbar circuit to protect the inverter is IMO not the right way to go. The idea is that it 'blows things up' to protect the inverter, and it would be better to have something that simply disconnects the turbine, and possibly switches on a diversion load at the same time. That can be done with an Omron voltage sensing relay and a double-throw contactor: Set the Omron up for overvoltage, with the shortest time-delay, and switch it so that when the grid is off the turbine is disconnected (with a dump load hooked up to the other side of the contactor). In case of overvoltage it will then also switch to the dump load. That should keep things under control, and protect the inverter. Something like the attached diagram.

A crowbar circuit may be additional security, something like a last-ditch effort to protect the inverter, but it shouldn't be the first line of defense.

-RoB-

[Edit: I've removed the original schematic, it had errors. Please see further down this thread for a better wiring diagram using an Omron relay (http://www.greenpowertalk.org/showthread.php?p=19849)

[Rob Littiken]

RoB
I agree. I'm planning on using the crow bar as a "just in case" last defense to keep the inverter from seeing 600V.

I noticed that on your over voltage diagram the relay is disconnecting the load from the rectifier/inverter and diverting it entirely to the diversion load. On Cor's diagram he made a few months ago he had 2 rectifiers and had the diversion load come on while still feeding the inverter.

Any thoughts on the +/- of each design.

Thanks,
Rob L

http://www.greenpowertalk.org/attachment.php?attachmentid=761&stc=1&d=1268002430

[Martin Gray]

All,

For the Omron to see all the voltage, from the three phases of the Wind Turbine.
Should it maybe run from rectified DC voltage. I drew a sketch to explain.

Also my turbine is high volts and low amps (10A) tops. So I substituted the 65A Telemecanique contactor, for a 18A-600v unit. LC1D18G7 a whole lot cheeper

Here's a link for the Contactor;
http://www.redrive.net/product/LC1D18G7/LC1D18G7-Telemecanique--Square-D--Schneider-Contactor-600V-IEC.html

Martin.

[Rob Beckers]

Martin, yeah, the contactor in my diagram is overkill for your application. I simply copied part of the circuit that we used on a Bergey Excel-S, and that one needed the large contactor. I should have erased the type label.

The Omron relay will work with AC or DC for its sensing. If your alternator is reasonably symmetrical then the voltage between one pair of phases should be the same as that between other pairs, so no need for a rectifier. It won't hurt, but it should work fine without the extra rectifier.

Rob, either way should work. The advantage of completely disconnecting from the inverter is that when the grid goes down, the turbine is disconnected and won't be able to do anything bad to the inverter. The advantage of connecting in parallel with the inverter is that the turbine will continue to produce energy even during overvoltage events. The dump load needs to be sized to handle the full load though, since it will have to keep things under control when there is no grid (and no inverter loading the turbine). Cor also uses an extra rectifier for the dump load; that can be useful if you can't put together a reasonably prized 3-phase one. It would have to be a beefy rectifier though, to make sure it will never blow (or you'll loose the ability to keep the turbine under control).

I wish someone made a voltage measurement relay like the Omron, but with a hysteresis and time constants (for entry and exit delay) that are adjustable. While this setup works, it will chatter quite a bit when the voltage gets near the overvoltage limit (voltage goes over, it switches to dump load, slows down the rotor, switches back to inverter etc.).

-RoB-

[Rob Littiken]

I wish someone made a voltage measurement relay like the Omron, but with a hysteresis and time constants (for entry and exit delay) that are adjustable. While this setup works, it will chatter quite a bit when the voltage gets near the overvoltage limit (voltage goes over, it switches to dump load, slows down the rotor, switches back to inverter etc.).

-RoB-

RoB
In looking for a relay for my system I came across the k8ab-vs3 it has the same specs as the k8ab-vw3 except with hysteresis. It's only SP not DP, but it doesn't seem like anyone is using the second pole anyway. Google it and you can find the specs.

Rob L

[Cor van Houtum]

quote
I wish someone made a voltage measurement relay like the Omron, but with a hysteresis and time constants (for entry and exit delay) that are adjustable. While this setup works, it will chatter quite a bit when the voltage gets near the overvoltage limit (voltage goes over, it switches to dump load, slows down the rotor, switches back to inverter etc.).

-RoB-

Hello Rob,

I am not sure what you mean now
in the original drawing i made there is the omron relay with hysterises time clock
I always use this type.

and i connect the relais to the dc site of things because of the voltage what is about 1.4 higher on the dc site
it is easy to make mistakes when you are monitoring on the ac site and want to protect the dc site

when connected in parallel the dumpload will be helped by the inverter and you are still harvesting power from the generator.

but all of this is in our new design not available anymore

today we are working with a complete windbox with the next functions

rectifier 100 amps
PLC that guards the voltage
adjustable with rs485 communication from attack 100 volts to attack 500 volts
The rs 485 interface to usb and the software are included.
relais that couple the generator always to the dumpload if no grid is available
dumpload that is in trangle mode over the generator
( one connection is constant the other two are swiched by a big relais)
Big box with door that makes it easy to service and connect.

look at my movie on the thread of the 2kw on the ground and not in the ground

and the most beautiful is that this total setup only cost 760 euro

[Rob Littiken]

Ok I think I've got the diversion load controller figured out. Can anyone tell me a good source for diversion load resistive elements. My systems is high voltage 500V and 6000W max. I hoping to build a large air heating unit similar to the one's in Cor's video and ARE systems use.
Once again, thanks for any help you can give.

Rob L

[Cor van Houtum]

I suggest a dumpload of 20 ohms 12kw

if you want to brake it on 500 volts

but if you have a inverter with a max input of 600 volts I would not risk
this high brake vallue.
let it brake on 400 volts or so that is much saver

if you have a dumpload of 12000 watts on 20 ohms
it will do

on 500 volts 12500 watts on 25 amps
on 400 volts 8000 watts on 20 amps
on 300 volts 4500 watts on 15 amps
on 200 volts 2000 watts on 10 amps
on 100 volts 500 watts on 5 amps

kind regards

Cor

[Rob Littiken]

Cor why such a large diversion load. I can see having some extra, like 8000W. 12000 is twice what the generator should make at max. Just wondering. Thanks for the input.

Anyone know of a source for the resistive elements in North America.

Thanks,
Rob L

P.S. RoB B this forum is sooo much nicer to use that otherpower forum. They have a great forum, just horrible software.

[Rob Beckers]

P.S. RoB B this forum is sooo much nicer to use that otherpower forum. They have a great forum, just horrible software.

That was one of the reasons for starting Green Power Talk. Now if only we could convince the others at OtherPower to come here... :D

-RoB-

[Cor van Houtum]

Hello Rob L,

This has to do with the way you want to use your brake

if you use 8000 watts then this will happen

on 500 volts 8000 watts on 16 amps you need a dumpload of 31,25 ohms
on 400 volts 5120 watts on 12.8 amps you need a dumpload of 31,25 ohms
on 300 volts 2880 watts on 9,6 amps you need a dumpload of 31,25 ohms
on 200 volts 1280 watts on 6.4 amps you need a dumpload of 31,25 ohms
on 100 volts 320 watts on 3.2 amps you need a dumpload of 31,25 ohms

If you are on a high wind area and you put your system on dumpload
because of reason you think is best.
the windgenerator wil start spinning up easy.
even do it is standing on the brake.

if a 6kw generator "feels" 320 watts as a brake dumpload at start-up it is just grinning a bit and starts to turn :laugh:

If you think that this is no problem and you do not want to use your dumpload as a brake
then 8000 watts should technicly be enough.
in the real world do I have seen generators rated 6kw that easely can do 10 kw for a few second when in extreme high winds.

it only needs a few seconds to kill your inverter.

Lets say it wont hurt to put some extra dumpload in the system and you sleep a lot better.

[Rob Beckers]

Rob, to get back to an earlier message: Yes, the Omron K8AB-VS3 would be a better choice since it lets you set a larger hysteresis than the -VW3 (that one is fixed at 5%). To switch back from overvoltage, and reconnect to the inverter, you want to wait for a lull in the wind, so a large hysteresis is in order.

As to the dumpload discussion: The way I see it is that your turbine needs some native mechanism to limit energy harvest in high winds. Furling is one. The dumpload is there to keep things under control up to that point where it sheds energy by some other mechanism. So, if an 8kW load (at the voltage where furling starts) does that job, then that's all it needs. It doesn't matter if the turbine spins while the dumpload is connected, as long as it doesn't run away before it furls. If your loaded voltage just before furling is very close to the inverter limit (say 500V DC) and you cannot reliably guarantee that a gust will not take it over 600V you need another mechanism to protect the inverter, such as a positive disconnect through a voltage measurement relay and contactor that disconnects the turbine. That little schematic I posted basically combines those two functions: When there's a grid and the voltage is under control it goes into the inverter, when the grid is gone or the voltage exceeds the set limit it goes to dumpload. The size of the dumpload is also fine line between what it takes to keep the turbine under control and not burning up the alternator!

Cor, what I meant was a relay that would let one set the hysteresis and the entr/exit delays. With the Omron relays only the entry delay can be set, and for overvoltage we want this as short as possible. It would be nice to set the exit delay to some reasonable value, like 30 seconds, so there's less relay shatter. Your new box sounds like a very nice project! However, for around a $1,000 it is a bit overkill for most applications that just need some under/overvoltage protection. An Omron relay plus contactor can do that job for roughly $200.

My 2.5 inflation corrected cents...

-RoB-

[Stewart Corman]

I have some surplus items that I have no intention of using anymore and it sort of fits this thread:

dump load:

I have verified the specs, and it is a three phase calrod element
rated at 20KW/208v rating total ..it measures 6.9ohms per leg x 3

I took a few quick photos (click to enlarge):
764
765


total length is 15 inches and it weighs 6 pounds
don't know if shipping to Canada is prohibitive?

Wired in series, it can handle 600v+.

BTW, be very careful in applying a huge resistive load suddenly as a brake for overspeed (becomes not much different than simply shorting the leads).
The inertia can snap a blade off like a twig.

also have some control relays and power diodes:
http://picasaweb.google.com/RobbieKayC/EBayElectronics#5295765601464575682
http://picasaweb.google.com/RobbieKayC/EBayElectronics#5295764927906099090
http://picasaweb.google.com/RobbieKayC/EBayElectronics#5295765080592327810
http://picasaweb.google.com/RobbieKayC/EBayElectronics#5295765225271136914

specs can be seen on labels in above photos (use zoom)

I would first have to lab test the diodes/bridges for breakdown voltage ..
S5502N - they are heafty ie 100amps at 1000v:

I haven't determined prices yet, but let me see who has interest and we can discuss offline

Stew Corman from sunny Endicott

[Rob Beckers]

Rob, saw your post at the other forum regarding dump load resistors, and checked Mouser's catalog. Those prices are actually not bad for 1kW resistors, even though that is still lots of money.

I can get diversion loads, build into a nice vented enclosure that can be hung on a wall. They are not cheap though, at around $930 for a 9kW diversion load (within reason the actual resistance value doesn't affect the price, it's power handling that you pay for). They get cheaper if you want more of them, much of that price is shipping (those are big, heavy boxes!).

-RoB-

[Rob Beckers]

To add to my last post, here is a list of cheap dump loads I've come across over the years, other than just big resistors:


Water heater elements (must be submerged or they'll burn up fast!), also available for battery voltages.
Baseboard heater elements, they come in sizes up to 2.5kW/240V.
Lightbulbs in series/parallel, the halogens come in large Wattages (resistance varies with temperature though).
Regular, cheap electrical heaters, the radiative type.
Electrodes stuck in a vat of somewhat salty water (better vent that hydrogen really well though!).


-RoB-

[Rob Littiken]

Been out the the country for awhile and wasn't able to respond to this thread.

I'm not looking to use the dumpload as a break to stop the turbine completely, just to keep a load on it to keep it from going out of control. Similar 17' Axial Flux machines have seen a peak max of 6000 watts, so I think about 8000 watts should be plenty safe.

My question is how will the different Ohm ratings of the elements effect the way the elements control the generator?

Thanks,
Rob L

[Cor van Houtum]

If you want to calculate the power in relation to the voltage
and you do not realy know how to do this then i suggest to go to
this site
http://www.ohmite.com/ohmslaw.html

there is a calculator on the main page of the site

have fun

[Rob Littiken]

I think I understand ohms law. I'm just trying to figure out sizing the resistor elements. I see they are offered at different amounts of resistance at a rated watt capacity.

I estimate my system to produce a max peak of 6000 watts at 500 Vdc, which is 12amps and a resistance in Ohms of 41.666.

So I guess I'm confused as how to correctly size the elements that are commercailly available to the system.

Sorry to be so electrically stupid.

Thanks for the help.

Rob L

[Rob Littiken]

To clearify what I am thinking. If I need 6000W 12amp 500Vdc 41 Ohms dump load and I wire 6- 1000W, 6.8 Ohms wound resistors in series it should have 6000W, 40.8 Ohms capacity.

Is this correct and is their anything I'm not taking into consideration?

Thanks,
Rob L

[Rob Beckers]

Yup, you got it right Rob! :)

-RoB-

[Jonathan Kraidin]

Look like I got here late in the discussion. I built my own grid-tie turbine using the Aurora 3.6kw inverter. I built my own rectifier and IGBT shunt controller. I use the controller to keep the voltage down if the grid goes offline. It also give the turbine a place to send the power.

You can take my schematic and design it to turn on at any voltage. Mine goes on at 230vdc. It requires no external power to operate. All you need to do is change the threshold diodes and the power resistor going to the voltage regulator.

Here is the schematic (http://www.mindchallenger.com/wind/wgpage16.html)

I suggest that you get non-inductive (not wire wound) resistors. This way, if you use a relay or semiconductor device you will not a huge inductive kick-back.

[Rob Littiken]

All,

For the Omron to see all the voltage, from the three phases of the Wind Turbine.
Should it maybe run from rectified DC voltage. I drew a sketch to explain.

Also my turbine is high volts and low amps (10A) tops. So I substituted the 65A Telemecanique contactor, for a 18A-600v unit. LC1D18G7 a whole lot cheeper

Here's a link for the Contactor;
http://www.redrive.net/product/LC1D18G7/LC1D18G7-Telemecanique--Square-D--Schneider-Contactor-600V-IEC.html

Martin.

Has anyone used this contactor? As far as I can tell it only has 1 set of Normally Open 3 phase contacts and 1 single set of NO contacts and 1 single set of NC contacts. It doesn't seem like this will work in the schematics shown in this thread. Am I missing something?

Thanks,

Rob L

[Rob Beckers]

Hi Rob,

You're right, the main contacts are NO and there's only one set. So, it's 3-pole single-throw. The other contacts are auxiliary, they're only good for a few Ampere.

By the way, you can get the heavier-duty 25A version of this contactor for less money than the 18A version.

-RoB-

[Rob Littiken]

I guess this contactor won't work for what I'm wanting. I want it to close if the grid goes down (it losses it's power) and put the dump load on. Anyone know of a part number for this type of contactor (3 phase, NC, 120V control voltage, 600V contacts capacity, approx 20 Amp) It seems like it should be easy, but I can't seem to find them online.

A contactor that would switch output between the inverter and the dumpload would be ideal, if anyone knows a part # for those.

Thanks for the help.

Rob L

[Stewart Corman]

Rob,
I think your paradigm is slightly skewed, unless I am missing something basic here.

1)You always have a source of 115v control voltage, either from the turbine and/or grid
2)You don't want the dump load to kick in unless grid is out
3)You want turbine to free wheel until you get to a minimum voltage
4) most 3 phase control relays are NO, so when power is out the load is off
5) you can use two control relays that are NO, one to turn on turbine at preset voltage, one to turn on dump load when grid goes off

The pair of 115v coil relay units I posted earlier can do the above, using the aux controller switches to pick off the coils:
http://picasaweb.google.com/RobbieKayC/EBayElectronics#5295765080592327810
current and voltage specs are much higher than you need

Stew

[Ken Hall]

I'm happy with the dumpload resistors I got from Milwaukee Resistor. Can't comment on price difference from other sources.

Ken

[Ken Hall]

Rob L,

If you find a source for a NS three phase relay, please let me know. I couldn't find one.

Ken

[Ulf Hansén]

I have send this before on another thread so I just copied,maybe some info

Trying to explain my box

There are two parts of my box
Swedish grid owners do not accept The inverters own protection against over/under
voltage,frequency on the 230 volt " side"
And I have to build in some other things to.

The generator can not restart by it self,you have to open the box and push a button and if grid power goes out it have to short cut the generator.

To protect the generator I use Cors Idea with the omron relay but I have added
a time relay omron H3DS-AL that is connected to a ABB relay that is closed when no voltage. The ABB relay is connected to a brake resistor.
So the function is.

1. push the green on button and if grid voltage, frequency are within limits the big cont actor pulls and get a self hold and connect to the inverter.
2. If voltage is below 400 V (adjustable) the omron relay pulls and connect to the time relay that is adjustable between parts of sec up to many hours .
3. When time is up the ABB relay opens and disconnect the brake resistor.
4. Generator starts turning
5. if grid power is out of value or dissapear the 230 v contactor falls and shut down the generator because the K8 relay lose voltage .The generator can not restart by itself.
6. If its windy and the generator produce to many watts the K8 relay dropps and the ABB relay lose voltage and brake the generator, but now it can restart by itself after the time is up on the time relay.
7. Hope this make sense

I have tryed to insert a drawing but failed but you can see it on this thread
http://www.greenpowertalk.org/attachment.php?attachmentid=766&d=1269802888.

I agree with Cor according to brake resistans and he helped me when I have burned the interface with dimesion of brake resistans
I have a 2kw gen and it was to small with a 5kw resistor. The generator didnt slow down in very hard wind .

Regards Ulf

[Rob Littiken]

Rob L,

If you find a source for a NS three phase relay, please let me know. I couldn't find one.

Ken

Ken I'm not sure what NS relay is. If your looking for a NC (Normally Closed) really I'm using the Telemecanique LC1D258. This has 2 NC contacts and you can just switch 2 of the 3 phase legs.

Rob

[Ulf Hansén]

Ken I'm not sure what NS relay is. If your looking for a NC (Normally Closed) really I'm using the Telemecanique LC1D258. This has 2 NC contacts and you can just switch 2 of the 3 phase legs.

Rob

Use this one works great
ABB ESB 24-04

http://www05.abb.com/global/scot/scot209.nsf/veritydisplay/25e8f26ce1493ca9c12574d500358fd2/$File/2CDC103005L0203.pdf

Regards Ulf

[Rob Littiken]

Use this one works great
ABB ESB 24-04

http://www05.abb.com/global/scot/scot209.nsf/veritydisplay/25e8f26ce1493ca9c12574d500358fd2//2CDC103005L0203.pdf

Regards Ulf

I couldn't find that ABB relay in the U.S. That why I went with the relay I used. Maybe someone knows where you can get them here.
Thanks
Rob

[Ulf Hansén]

Try here
http://www.abb.us/cawp/usabb046/cbf8efcdc48e0c7985256bbc005184a2.aspx

Ulf

[Cor van Houtum]

As I was the one who introduced the omron relays to you I think that I also must tell you the disadvantages we found.

when a trigger level is reached the relays will be activated
to prevent hysterisses the time off attack can be set.
the disadvantage of this system is that the time should be estimated and is not related to the real behavour of the windturbine
so it could be that the attack of the relays is to short or to long.

A better way to measure this attack time should be a upper and a lower value
lets say you want your dumpload go on at 300 volts,
the wind is gusting
your Omron will keep the brake on for 10 seconds (example)
But you could never be sure that this is enough to brake the turbine.

I changed to other hardware to overcome this problem.

I use a SIEMENS LOGO 12/24 PLC UNIT
This PLC has 4 output relays and 8 inputs
The inputs could be all digital but it has also the oppertunity to use 2 of the inputs as an analog input.
the input 7 and 8 can be used as a analog 0-10 volt input.

this means that we could use this input to monitor the dc voltage from the generator
and switch the output relays according a plc program.
the small output relays can switch a power relays that can switch the dumpload.

I have programmed this PLC as a dumpload protection and let the output relays switch on a upper attack voltage and keep this status as long as the input senses the lower trigger level.
then it will release the relays (so also the dumpload) and will repeat this action over and over.

this works great.

but as i sayed before there are 4 output relays on this plc

now it is also possible to use a second relays output to activate a power relays that connects/disconnects the DC output to the inverter.
the trigger level can again be activated in the next ladder of the plc program.
It is easy to put a timer in the program and use the input from the analog rmeasurement as a reset value.
then you can be sure when the DC to your inverter is restored that this is only done when the voltage is far within range.

kind regards

Cor

[Ulf Hansén]

Thanks Cor
I have to look at a PLC,but I have used a time relay( omron H3DS-AL) after the omron so even if the Omron goes on after 10 sec the generator is brake 15 minutes (you can adjust between 0.1 sec to several hours) the dissadvantage is when you start it up, I have to wait to the time goes up,in my case 15 min.

Cor I have a question
Can I use a bigger generator for ex 5kw to a 3,6 aurora inverter as long as I dont go over max 600Vdc?
Im thinking of putting a 5kw and use the inverter in first stage in lower winds and in higher winds shift over to a heating element in my accumulator tank (750l) of water
I have tryed to fined somewhere I can read about how inverter works,How it can harvest power,do you have any tip where I can find that?

Regards Ulf

[Cor van Houtum]

Hello Ulf,

this is no problem

you can put whatever power on a inverter
when it is bigger then the inverter can do then this will become no problem

however problems can and will come if your voltage goes over limits
also amps over the limit wil the inverter stop

with volts over the limit the inverter will stop also and when you open it then you will see that a inverter works on smoke,
cause when the smoke is out the box then it does not work anymore :D

Cor

[Brian McGowan]

Rob Beckers writes in this thread on 13th March 2010, 07:10

“Electrodes stuck in a vat of somewhat salty water (better vent that hydrogen really well though!). “

If you get to a point where you have enough extra power to make hydrogen and want to keep it let me know. I have mostly designed what I think it is a nice hydrogen generator that I think can sink 60 amps in 20 amp chunks. It should be fairly inexpensive as it is made mostly of plumbing parts from Home Depot. I have most of a prototype together but I stopped working on it when I decided it would work and that I wasn’t making enough power to make that a priority and I should concentrate on making power and worry about dissipating extra when I actually have it. It would appear some of you do have this much extra power. I use salty water for it which is why this came to mind when I read the above statement.
Brian

[Cor van Houtum]

As Rob stated before it could be a overkill in price when using all of the components in my solution.
So I went back to the start of the problem.

The windbox that is original from power-one Aurora and the Aurora inverter.

Insite the windbox is a IGBT that makes the dumpload contact
this is activated at a voltage of about 530 volts and makes it in most cases unusable with a small turbine (2 Kw)
these turbines are mostly made to charge battery's and produce there rated power at a voltage of 140 volts
It is no problem to let the turbine turn a bit faster and go to 200 volts Dc but going faster as this will make it noisy and dangerous.

So we need to dumpload at about 210 volts
when these turbines are on the loose they can do easy 700 volts or even more and will destroy the Aurora inverter.

Looking to the inverter box you find a big space to make your connections
this is the perfect place to put in a siemens logo PLC on a small din rail
you can fit it on the cover (backsite)
Also a 20 amps siemens power relays and the siemens powersupply can be on this rail

Now you got a nice set-up with 3 components that are sized and coloured the same
and even the connections are proper isolated.

Insite the inverter i have allready the grid connection
also the DC input is there

parallel the grid connection and bring it to the logo powersupply.

Later I will make a drawing and some foto's to show you

I have written a program for the siemens PLC that does 2 things only

1 ) it closes the contact from the 20 amps relays when the voltage is lower then 400
volts.
this relays is used to connect/disconnect the input DC from the inverter
this way it is protected all the time against overvoltage

2 ) it closes and opens a second relays-port on the PLC that is connected to the gate of the IGBT insite the Windbox.

This way you can activate the dumpload that is connected .
depending on the setting in the program you can choose the voltage of attack and the voltage of let go free.
(upper and lower voltage setting)


What we got now is we use the original windbox and the inverter
no need for more boxes
absolute overvoltage protection on the inverter
dumpload voltage can be set according needs of turbine
hysteris is not there because of upper and lower voltage setting
when the grid fails then the dc input from the inverter is separated

The power relays has also a normal closed contact
we use this to connect the dumpload direct to the generator when the grid fails

so the only thing to do is to wire some extra wires between the windbox and the inverterbox

but as you know are these boxes very good made with cable in and outputs
so this is not a problem.

The siemens logo relays has 3 make contacts
every contact can have 20 amps
we use them all together and have 60 amps of contact power
there is no reason to not use the contacts as they are allready there.


what you think ?

Cor

[Cor van Houtum]

as I explained in my last posting I have tested the new controller setup
this works good

look at the picture

The IGBT that is insite the windbox can be triggered with a 12 volt signal
the powersupply from the siemens logo plc is also 12 volts
so bring this 12 volts over the plc relays output q2 and then to the gate of the igbt

when the plc switches the output then the dumpload will go on and off

you can leave the original cables from the igbt as they are
just parallel the 12 volts switching trigger voltage to the gate input (white cable)

[Ken Hall]

Cor (and others),

I've had three failures of the Aurora Windbox due to the dumpload circuit failing on.

Is there anything wrong with using a relay to add a dumpload between the SWG rectifier and the Aurora inverter.

If I use the Telemecanique LC1D258 with its 2 NO and 2 NC contacts, and use the NC contacts only, I could have the 20 ohm dumpload I had wired to the Windbox take effect both on overvoltage (using two OMRONs, one for sensing and one for delay) and on loss of grid.

Note for others, my SWG controller does not work when the grid is off.

Since I'm adding to the DC power path and not switching, will DC arcing be a problem? Most of this thread has been about adding the dumpload to the AC side.

Thoughts?

Ken

[Rob Beckers]

Hi Ken,

A 20 Ohm dump load is pushing it for the PVI-Wind-Interface box; That puts it right at the 30A limit by the time you reach 600V. Your experience shows it's probably beyond the limit (and Power-One is 'optimistic' in putting the current limit at 30A). In my opinion the whole dump load option of the wind box is pretty useless, as it only comes on at 530V DC. Too close to the 600V limit for comfort, and most turbines have at that point run away so badly that a dump load won't reliably control them any more.

You cannot use that contactor to switch DC. It will result in welded contacts in short order. I suppose the issue is that you already have a single-resistor dump load that you want to use. I suggest buying a cheap-and-nearly-indestructible 3-phase bridge just for the dump load (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CC1660-ND), and instead switching the AC side with the contactor. You only need 2 contacts to do 3-phase switching (just leave one phase permanently connected). The AC goes through the bridge, bridge drives the diversion load. The rectifier needs a heatsink; either an actual heat sink, of by bolting it to the chassis of something with lots of metal to disperse the heat (the bottom of the dump load housing? Should stay cool enough there).

-RoB-

[Ken Hall]

Rob,

Thanks for the advice. Price is certainly reasonable (cheap even).

FYI, I asked Schneider their opinion on using the Telemacique relay for DC and their answer was -- The D-line contactors can handle DC voltage per IEC standards but they are not UL listed for the application.

Sounds like they're trying to straddle the fence.

My resistor box is lightweight AL sheetmetal. I'll need to bolt a good slab of metal to use it for a heat sink.

I just generated my 725th Kw-hr with over 1 yr in operation. Not very impressive. I've lost about 5 months waiting on Windbox exchanges. I'm not ever going to cover operating costs. But, getting things to work has turned into a "fun" intellectual challenge.

Ken

[Rob Beckers]

Ken, despite Schneider's comment I would recommend using the bridge rectifier and switching AC. It will make it much more reliable long-term, for very little money. The alternator (and wiring) has an inductive component to it, switching that off will cause an amount of arcing, and that is much worse on the contacts for DC vs. AC at those voltages.

Small wind turbines seem to rarely "make money". Your experience is pretty well the standard (sadly)...

-RoB-

[Steven Fahey]

Rob,

I just generated my 725th Kw-hr with over 1 yr in operation. Not very impressive. I've lost about 5 months waiting on Windbox exchanges. I'm not ever going to cover operating costs. But, getting things to work has turned into a "fun" intellectual challenge.

Ken

Welcome to small wind power Ken! Keep doing it for the fun. There are more expensive hobbies out there.

[Ken Hall]

How big a piece of metal do I need for a heat sink? Deck of cards? 2 decks? Al or steel? Do I need heatsink grease?

Thanks,

Ken

[Rob Beckers]

Hi Ken,

The heat sink on the original wind box from Power-One is roughly 15x5x5 cm with fins (to increase surface area), and it is on the small side. If you have just a flat metal plate you would need a fairly large area, possibly around 1.5x the size of a piece of paper. If you have a real (aluminum) heat sink with fins then something much more compact will suffice. If I have some time I can do the calculation and show you a link to commercial heat sinks that would do the job.

Yes, you definitely want to use thermal grease between the rectifier and heat sink. Without it the thermal conductivity between the two is very poor.

-RoB-

[Ken Hall]

Rob,

Cut up 4 feet of 2x2" of 1/8 inch AL angle iron and made a doubled U shaped heatsink (four fins, 1 foot long). Attached it to a foot of straight 2" AL on which I mounted the rectifier. Smeared two little tubes of heatsink grease all over.

Attached by one fin to 2 feet of AL which bridged my dumpload brackets.

More mass and surface than a windbox.

Other than a bird's nest of wires all over, I think I'm now good to go -- NS contactor for loss of power shutdown. High voltage sensing relay going to a AC to DC dumpload, off switch shorting everything together + all the SWG controller features.

Of course, the trees have all leafed out and my output has dropped dramatically - the joys of a short tower.

Thanks for the help.

Ken

Ken

[Rob Beckers]

Sounds good Ken! When you have some time post a few pictures of your turbine and setup. All you have to do now is wait for the next thunderstorm (I mean the wind that goes with it, not the light show)...

-RoB-

[Dale Sheler]

I see a lot of relay stuff going on here and talk of wishing for controlable hysteresis, I know a couple folks using the relay driver from Morningstar, they are almost infinitely programmable seems like they can make relays do just about anything.
http://www.morningstarcorp.com/en/relay-driver

[Rob Beckers]

Thanks for the link Dale! I didn't even know Morningstar makes these.
We've been using Omron measurement relays to do similar things; they have a selectable hysteresis, the tripping voltage can be set, delay time etc. There are several versions in the series, the one we use most is the K8AB-VS3, the version for a 120V supply (www.ia.omron.com/data_pdf/).

-RoB-

[Dale Sheler]

I didn't either till Chris Olson got one, he really likes it, with the software you can make simple relays do just about anything.

[Chris Olson]

I didn't either till Chris Olson got one, he really likes it, with the software you can make simple relays do just about anything.

This is true. I had mine set up for load control and generator start originally. When we got the Jake turbine running, we bought a Generac EcoGen standby generator and a GSM for the inverter so the inverter handles all the generator start and stop functions. So I'm using it purely for load control now.

Channel one turns on the first element (the lower one) in our water heater at 28.5 volts and leaves it on for 15 minutes. Then the RD-1 looks at the system voltage and if it's still above 27.0 it leaves it on for another 15 minutes, or until the voltage drops below 27.0 volts. Both elements are powered at 240 volts from our inverter.

Channel two turns on the second element (the top one) at 29.0 volts with a 9 minute on time, then checks the system voltage and if it's still above 28.0 it leaves it on for another 9 minutes, or until the system voltage drops below 28.0.

Channel three is configured as a temperature sensor input from a sensor on the water heater. If the heater tank gets to 170 degrees it shuts off both elements and channel four shuts down the solar array and wind turbines and leaves all incoming power shut down for a minimum of 10 minutes, then checks system voltage and leaves the incoming power sources shut down until the system voltage drops below 26.0 volts.

The RD-1 is more configurable and "tuneable" than an ALM (Auxiliary Load Module) for the inverter. It has configurable timers for all four channels up to 18 hours in 1 second increments. You can set min/max on and off, voltage trip points with delay times before it switches from High to Low or Low to High, configure any of the channels as inputs and use both system voltage and one of the input channels for it to make decisions on what to do on another channel, and many other things. They call it a relay driver but it's really a programmable logic module that controls things by turning relays on and off.

The only downside to the thing is that it has to be programmed with a laptop and a serial cable using Morningstar's MSView software. It's easy to program, however, just that it would be nice to have an onboard menu on the thing instead of having to hook up a laptop to program it.

The thing isn't very big either. I got it mounted on the wall in our utility room right alongside the generator transfer switch
--
Chris

[David Carr]

This seems like a really dumb question because I have a lot of experience installing wind turbines, but I'm stumped. I see that this thread has people who have used the power-one interface so I hope someone here knows the answer. All last week I could not get a power-one representative on the phone to help.

We have never encountered a connector block such as the one in the power-one wind box interface. Can you provide any advice on how it is supposed to work? There are two holes to each connection, one smaller and square and the other larger and round through which you can see copper connection block, but neither one seems to work well for connecting wires to it. The best we can come up with is that the smaller square hole is the connection point and the wire is held only by tension of the plastic tabs, but it does not seem like a good solid connection(Can just pull the wire right out). If you have used this, please provide some detail. It must be a super simple answer, but it has not been obvious to me and my crew.

Thanks,

DC

[Rob Beckers]

Hi David,

You could have given me a call... ;)
Those connectors work by inserting a small flat-blade screw driver in the narrow slow above the (larger) wire opening. The screw driver is then used as a lever, pull it away from the printed circuit board, to move the blade in the wire opening up, so you can shove a wire under it. They're an absolute pain to work with, though very reliable once the wires are in (no bolts that can come loose over time). If you want to keep life simple, use 10 AWG wire for the wind box, and convert to something thicker (if you need it) elsewhere. Trying to get 6 AWG wire under those terminals is a nightmare. Don't ask how I know.

-RoB-

[David Carr]

I actually figured it out finally yesterday. I am surprised that Aurora does not explain that in their instructions, or print it on a sticker in the box. Thank you for your informed reply.

DAvid

[John Szegda]

Hello RoB,

I finally got My Exmork 2KW flying. I must admit the unit is putting out a lot of wattage and is working great. I love the 1950's technology, it's built to withstand bullets.
My problem is with the Controllers. I bought two Turbines with Controllers for backup.
Unfortunately one Controller lasted two days and the other smoked a chip. Spoke with Exmork and they will repair them, but I have to pay shipping. I don't know how long it will take for repairs, so I was thinking I could put together Omron Protection System
according to your Schematic. One question I have is, the K8AB-VW3 is powered 120v
from the Grid. If the Grid is down, how will the K8AB activate itself.

John

[Rob Beckers]

Hi John,

With a NO ("normally open") type contactor the connection to the controller/rectifier/inverter will automatically open when grid power goes down. So, even if the grid falls away the electronics are protected.

I've updated the schematic for overvoltage protection, it is attached below. I'll remove the original one at the beginning of this thread (it has errors on it anyway), and replaced it. The new diagram has two options: One is to just disconnect the electronics on high voltage, the second one adds support for switching on a dump load.

As before, the method is fail-safe: When the grid goes down the electronics disconnect and the dump load is connected to keep the turbine under control.

-RoB-

[John Szegda]

Hi RoB,

Thanks for you response. On the schematic you show a small box with a hash thru the center, with a lead connected to K8AB number 12 screw and back to A1 neutral feed. can you tell Me what it is and it's function.

John

[Rob Beckers]

John, that's the coil of the contactor. The contacts of the contactor are drawn right above it. So, the Omron switches the contactor on/off, and the contactor takes care of disconnecting the electronics in case of overvoltage or when the grid is not present.

-RoB-

[John Szegda]

Hello RoB,

Well I made a big blunder. I was testing one of the controllers and when I was done unfortunately I forgot to disconnect Aurora Inverter. That night the winds picked up and consequently fried the Inverter. I assume over voltage is not covered by warranty. Do you know a technician that may be able to repair this unit, other then Power One. Also, I tested the 2KW Turbine today and was getting DC voltage readings of 962V with a 12 MPH wind. Is this common or will I need to step the voltage down with an additional device when I re-install the Inverter.

Thanks,
John

[Rob Beckers]

Auch! Sorry to hear about your mishap John!
I don't know anyone other than Power-One repairing inverters. Power-One has a fixed fee to fix out-of-warranty repairs (give your supplier a call and have them ask, you need an RMA number before sending anything back). They don't actually 'fix' anything but send you a new inverter after you send in the broken one and pay the fee. By the way, the inverter sets a flag in memory just before the smoke is let out, so Power-One can see it was killed due to overvoltage, and warranty does not cover that.

That 900+ Volt DC you measured was unloaded I assume? All wind turbines will reach very high voltages when running unloaded (except for drag devices such as Darrieus turbines), they just keep speeding up until the power extracted by the rotor matches the power used up in aerodynamic drag of the rotor. Depending on the specific turbine that can easily get to 1 or 2kV.

That's why I keep telling people their turbines must have a way to keep their RPM under control if there is no load (such as when the grid is down, which typically happens during a storm just when winds are strong). Does your turbine not have a dump load that switches on at a set voltage to keep it from running away? Besides inverter failure you're risking mechanical failure of the turbine: To reach those voltages it has to be spinning at least twice as fast as it's supposed to during normal operation.

-RoB-

[John Szegda]

Hello RoB,

Sorry for not getting back to you sooner, I've been busy with business. I contacted Power One and got a RMA number. They told me the out of warranty repairs would cost
$740.00 plus shipping ($132.00 round trip). With these numbers, I will pay more attention next time. The Controller did have a dump, but it was not working. The controllers are in China at Exmork for warranty repairs. RoB, on your schematic scheme 2,
when the LC1D258G7 is activated it powers a bridge rectifier. The other end of the rectifier will produce DC positive and negative. What prevents the resister from blowing up.

John

[Rob Beckers]

Hi John,

The big resistors used for dump loads are nearly impossible to "blow up" in the traditional sense. They're space heaters. If you overload them they'll get red-hot, start to smell bad, and that's probably not a great idea, but they'll hold together. Of course, the rectifier shown in there has its limits, as does the contactor, so you want to size things such that it's realistic. Overloading a dump load also means you're probably overloading the alternator of the turbine, and it is far easier to blow up the alternator (they don't tend to be massively oversized because that costs money) than the dump load.

To the drawing, in particular option 2 with the dump load, I should add that you don't have to use a rectifier. It's entirely possible to make a 3-phase dump load (just use 3 resistors). I just wanted to point out that you can use a single-resistor dump load by incorporating that rectifier.

-RoB-