Classic/Clipper MPPT Wind Turbine Controller

keyturbocars

I decided to change my original post and make it more of a comparison between 2 wind turbine controllers that I have. The first is the original controller that came with my existing HY-2000 2kW wind turbine. The second one is a controller that is from a past 2kW wind turbine that failed.

I am interested in the Midnite Solar Classic MPPT controller and the Clipper, but I need to wait and see how it works in the real world once it is released. In the meanwhile, I'm trying to get my existing wind turbine system set up to be as reliable and safe as possible.

First, some information on the HY-2000 wind turbine cotnroller. The only thing that has changed since I took these pictures is that I have set up a pair of 120mm Pabst fans with a thermostat to cool the rectifier and circuit board. The fans are low power (60ma at 24V - have 2 wired in series for my 48V system), but move plenty of air through the HY-2000 controller. I didn't like the way the HY-2000 controlller was set up with passive cooling and inadequate (in my opinion) vent openings in the case. Might be fine under lighter load, but when the wind roars down here, then I want to make sure that I don't have any failures due to electronics overheating. Most likely time for something like that to occur would be during powerful winds when the rectifier is cranking out a lot of heat. That's the WORST time to have a controller failure and out of control wind turbine!

More to follow on my other wind turbine controller...

keyturbocars

Re: Wind Turbine Controllers

Here are some pictures on my other wind turbine controller.

I am not an electrical engineer or an electronics expert, but my impression is that this one is a better designed/built controller. This controller has a 200a rectifier (while the HY-2000 controller has a 100a). This controller has a MOSFET dump, while the HY-2000 has relays. There's something about the clicking of the relays when the wind is roaring that makes me a little nervous on the HY-2000.

In any case, I'll attach some pictures of this other MOSFET wind turbine controller.

There are 3 MOSFETs attached to a heat sink. They are made by IXYS and their part number is: IXTQ82N25P . Here's the spec sheet on it.

http://ixdev.ixys.com/DataSheet/99121.pdf

It lists a maximum amperage of 82A.

I've got 3 questions for you electronics experts...

1) Does the 3 of these MOSFETs mean that they can control a maximum of 3 x 82A?

Just curious what the power capacity of these 3 MOSFETs really is, and if they really made this controller with that big of a factor of safety. Related to factors of safety...

2) Could 2 more identical MOSFETs be solderd to the board and increase the current switching capacity further, or would the rest of the circuit board not be able to drive the 2 additional MOSFETs?

That might be a dumb question, but I am not familiar enough with electronics to know. The 3 MOSFETs might be more than adequate as is. The most I've ever seen from my wind turbine is 65A (3.5kW) for very short durations of time during strong wind gusts.

In the closeup picture of the MOSFETs, there are 2 variable resistors in the left corner. One is labeled VR1 and the other VR2. I experimented with them and found that if I adjust one of them (can't recall right now which one), then I can change the dump load voltage.

3) What would that other potentiometer be likely to change if the other one changes the dump load trip voltage?

I've seen other dump load controllers that also have 2 potentiometers like this. One changes the trip point voltage, but I am curious what the other POT is likely to change.

I've hooked up this MOSFET controller for now to see how it works with the HY-2000 wind turbine. One of the first things I am going to do is to replace the wire connecting the large dump load resistors with some high temperature heater/appliance type wires with high temperature ring terminals. Those normal insulated wires look dangerous to me (meltdown). Another thing you might notice is that the fan for the circuit board is held down by wire. I know, it's redneck! I didn't like the bracket that held the original fan, because it blocked the flow of the lower section of the fan significantly. The way I wired it down, it doesn't block the airflow at all. I also replaced the original fan with a higher quality Delta fan.

Thanks for your opinions on these controllers.

Edward

MisterB

Re: Classic/Clipper MPPT Wind Turbine Controller

If the mosfets are wired in parallel, then the current rating would be combined but it wouldn't be a good idea to run them at the maximum capacity and looking at the spec sheet, it would be safer and they would last a lot longer puting 60 amps through each one. The 2 pots could be wired in series for course and fine adjustment--if they are different values this could be the case but I wouldn't think you would need that kind of adjustment for a controller. Another possiblity is that this is a 2 step controller and has 2 trip points which might be why mosfets were used instead of a relay. Mosfets can be used like an electric valve and you can control the current flowing from the source to the drain by the voltage applied to the gate.

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

Thanks for the reply MisterB. I am trying to decide if it would be beneficial for me to add 2 more of the same IXYS MOSFETs to increase the reliability of the controller. I'm pretty sure that this circuit board is used for larger wind turbines as well, since the board has spots for 2 more MOSFETs and the heat sink is drilled/tapped for them too. I just don't under electronics enough to know if a couple more of these MOSFETs could be added without changing anything else on the board. I'm not sure if the rest of the circuit would be able to support 2 more MOSFETs. And it might be totally unnecessary. With a maximum 65A & 54V (3.5kW) output of the wind turbine, then the 3 MOSFETs might be more than adequate as long as they are kept cool.

I would rather have as much factor of safety as possible, because I know what it's like to have an out of control turbine and I don't want to ever experience that again! That's why I'm doing all this. Trying to make my system as reliable and safe as possible.

I know that the one of the potentiometers (VR1 & VR2) controls the dump load. I've got some written notes somewhere (can't find them at the moment) where I documented which VR changed the dump load voltage trip point. I ran with this controller on another wind turbine for several months and I got to know how it behaves. The dump load was single stage at a set voltage. I could tell what it was doing because the fans would turn on/off with the dump load, so I could hear what the controller was doing. During high wind gusts, the controller would pulse the dump load on/off rapidly to slow down the turbine. If the winds were strong enough, the dump load would switch to continuous to try to slow the turbine. The dump load is 4kW heating resistors. I liked the way the controller would try to slow the turbine in high winds. That's one reason I am experimenting with this controller again. I want to make my system as safe as possible.

mike95490

Re: Classic/Clipper MPPT Wind Turbine Controller

To make it more reliable, I would remote the dump load, so it can't possibly heat the control.

Make sure the power semiconductors are properly heat sunk, greased and clamped, then reflow the solder at their connections. That releives the stress on the solder joint.

A good controller, in high winds, slows the turbine down, and then shorts the output to stop the blades. But don't short the output while spinning.....

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

Good points Mike. This controller seems well designed in many ways, but the biggest problem with it's design is cooling. The way it was set up, the heat from the dump load would definitely be drawn around to the other side and cause the rectifier and circuit board to get heated. Very poor design in terms of cooling. One of the first thing I did was add a piece of sheetmetal to extend the "wall" between the 2 halves to better separate those sections. I also ran it with the cover off so the dump load heat would go up and away from the controller. Worked very well. I do plan to remotely mount the dump load in my garage eventually if this controller proves to be the one that I keep using.

I'm trying to decide if it's worth considering adding 2 more identical IXYS MOSFETs for an extra measure of power handling capacity. I'm not even sure if that's possible without changing other components in the circuitry. In my mind, I sort of view the MOSFETs as solid state relays (I know they are not exactly the same). My thinking is that if I added 2 more then I'd be sharing the load over more components and increase the reliability and long term life of the controller. I do not want to have a controller failure and an out of control turbine!

mike95490

Re: Classic/Clipper MPPT Wind Turbine Controller

You would have to examine the PCB traces for the MOSFETS to see if they are in parallel or not. Then you need 5 new, MATCHED MOSFETS, so they share the load evenly. Also, a small ballast resistor in each MOSFET lead helps share current. MOSFETS like to be full on or full of, it's the inbetween state where they heat up and go non-linear. So I can't really advise you about them, except the drive circuit should be able to drive 2 more, if it was designed properly. (Which not all stuff is designed right)

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

Thanks for your electronics help Mike. That is an area where I am lacking in depth experience or knowledge.

The spots on the board for the other 2 MOSFETs are in parallel with the existing 3 MOSFETs. The controller that I have is made in both 2kW and 3kW versions. In fact, the shipping carton even shows both 2kW and 3kW options, and then in my case the 2kW option is checked off on the box. So, it appears that the same circuit board is used on both the 2kW and 3kW versions of this controller, and they just use the 3 MOSFETs on the 2kW version and the 5 MOSFETs on the 3kW version. I just don't know if they do anything different with the drive circuitry on the 3kW version.

If I were to source 2 more of the identical IXYS MOSFETs, then shouldn't it be OK to just install those rather than replacing all 5?

If the drive circuitry was not designed for 5 MOSFETs on my board, then what would be the risk or consequences of adding the 2 MOSFETs. My main motivation in exploring this is to see if I can improve reliability of the controller. If I add 2 more MOSFETs and do more harm than good, then I'm "shooting myself in the foot"! I've done that before in the process of trying to improve things. Perhaps I should just concentrate on improving the cooling of the existing MOSFETs with a higher flow fan.

My background is mechanical engineering and I like big factors of safety! So, I would rather error on the side of overkill, rather than have something fail at just the worse time! The most likely time this controller would fail would be during a big wind event and the controller is having to handle 3.5kW surges for an extended period of time. That is not the time for me to find out my controller is inadequate!

mike95490

Re: Classic/Clipper MPPT Wind Turbine Controller

keyturbocars wrote: »

If I were to source 2 more of the identical IXYS MOSFETs, then shouldn't it be OK to just install those rather than replacing all 5?

I think I recall that power MOSFETS need to be in a matched set. Otherwise, the low voltage one hogs all the power till it burns up, then the next lowest one....
This happens in less than a second. When the MOSFETS fry, they usually short all connections together, which also frys the driver. NOT GOOD !

matching is usually within 1 hundreth of a volt, requiring a Curve Tracer. A single FET to handle the power is quite expensive, which is why they use small ones in parallel. Large OEM companies order parts in matched "Bins" so they are all the same, till the next order.

MisterB

Re: Classic/Clipper MPPT Wind Turbine Controller

Matching considerations aside, I wouldn't do this mod without a schematic for the 3kw board because there might be something else changed that isn't so obvious like a different value resistor somewhere on the board.

Moving the dump load is easier and safer. Field testing the controller with the box open under moderately high wind conditions and measuring temperatures with an infrared remote thermometer would be a good idea because you can see if there are overheating issues and pinpoint exactly where they are and how bad they are.

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

I am concerned about adding 2 more MOSFETs without knowing for sure how it will affect the whole circuit. Getting a schematic from China will probably not be possible.

One interesting thing about the MOSFETs on this board, it appears that there is no thermal grease between the MOSFETs and the heat sink. These IXYS MOSFETs have the metal tab electrically connected to the drain pin. The heat sink is actually used as a conductor along with the drain pin on the MOSFETs. The heat sink is physically screwed to the board over copper traces that connect it to the output wire going to the dump load resistors.

I read somewhere that sometimes heat sink grease is not used on MOSFETs for this reason. Sort of concerns me about the ability for the MOSFETs to transfer heat effectively to the heat sink, but adding grease might create other problems if the board was designed with the heat sink considered as a sort of electrical bus.

mike95490

Re: Classic/Clipper MPPT Wind Turbine Controller

There is conductive and non-conductive grease. But if that is an aluminum heat sink, you will have trouble in a year or less, as untreated aluminum oxidizes rapidly to an insulating film. That's part of the trouble with alum wire, which needs No-Ox grease at connections. If the connection from MOSFET tab to alum heatsink is carrying power, you will have trouble - unless the aluminum has been properly plated and solder tinned, which is what we do with spacecraft modules. I doubt this has been done on your controller.
If you really think your heatsink is carrying current (usually the center pin of the 3 pins is connected to the heat tab) you should remove heatsink and use aluminum wire no-ox paste on it and the tabs, bolt tightly, and reflow solder. But I can't belive they use the heatsink as conductor.

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

Yep, it's true. I just double checked and the heat sink bolts down onto a big tinned trace on the circuit board that goes to one of the wires that goes to the dump load resistors. It appears that they are using both the drain pin on the MOSFET and the metal tab which is screwed to the heat sink. I checked continuity between the top of the heat sink and the dump load wire and it's 0.3 Ohms, so it's connected and part of the circuit.

You are right, the IXYS data sheets shows the center pin and the metal tab as both being "drain (collector)".

Does the No-ox also have heat transfer properties?

Is this the right stuff that I should use (they list it as "conductive")?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270664768335

Thanks for your help Mike!

mike95490

Re: Classic/Clipper MPPT Wind Turbine Controller

keyturbocars wrote: »

Does the No-ox also have heat transfer properties?

Is this the right stuff that I should use (they list it as "conductive")?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270664768335

Thanks for your help Mike!

The no-ox I'm speaking of, is from electrical supply houses, for aluminum wires, it has tiny metal crystals that as you rub it into the aluminum wire/heatsink, it scrapes off the oxide and maintains electrical conductivity. So I'm sure the metal particles will also help thermal transfer too. Has to be better than plain air gaps. You want the heat sink bolts snug, but not so tight they deform the soft aluminum.

The clear grease in the ebay ad is not no-ox for aluminum wire.

Also, these parts are highly static sensitive, and you need to take precaution to not blow them out as you work.

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

I did some more searching and I think this is the no-ox paste for aluminum wire. At least, they make reference to using it for AL wire.

http://www.sanchem.com/aSpecialE.html

If it's something different, then please let me know. Thanks.

mike95490

Re: Classic/Clipper MPPT Wind Turbine Controller

keyturbocars wrote: »

I did some more searching and I think this is the no-ox paste for aluminum wire. At least, they make reference to using it for AL wire.

http://www.sanchem.com/aSpecialE.html

If it's something different, then please let me know. Thanks.

That stuff looks like it works, you have to rub it around a bit to clean the oxides off, then bolt it together.

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

Thanks Mike. I'll plan to buy some of that stuff.

mike95490

Re: Classic/Clipper MPPT Wind Turbine Controller

Thin coat, just enough to fill in the gaps, you don't want goo to get all over the place when it warms up. Less is generaly better than too much, espically if it works with none.

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

I thought I'd post an update on this. I ended up discovering without a doubt that I could add 2 additional MOSFETs to this circuit board. I consulted with some electronics experts and they confirmed that this circuit board is the same as used on 2kW and 3kW controllers. The circuit board in my 2kW controller has 2 empty places on the board for 2 additional MOSFETs. Gate driver circuit is made for 5 MOSFETs and gate resistors are already there. Everything is ready for plug and play. I sourced 5 of the exact same IXYS MOSFETs. I decided to replace all 5 as a set. Anyway, I didn't get that far yet, because wind was calm and I was distracted by other things.

Today, we had some stronger winds that were peaking in the 30mph range, so I was able to do some more testing on this MOSFET controller. This is what I found out. The controller circuit is programmed to limit power output to 40.0A (very precisely). When power hits 40.0A, then the circuit pulses the MOSFET gates and loads down the turbine with the 4kW resistor heating elements. This continues as long as the wind is strong and holds the max power output to 40.0A (2kW). I like this safety feature of the electromagnetic braking, but the limit on this other controller is set too low for my HY-2000 turbine.

With the other controller that came with the HY-2000, I would have been seeing 60A surges during the 30+mph winds. I've seen as high as 65A surges before. Now, too much of a good thing can be bad, which is why I'm looking into using this other controller. I am now investigating if there is a way to change the power limit on this controller when the electromagnetic braking takes effect. If I could change it from 40.0A (2kW) to 60.0A (3kW), then I could take full advantage of the power available, but still have the safety of electromagnetic braking.

I found out that at 40.0A (2kW), the HY-2000 is spinning around 550 RPM. At 60.0A (3kW), the HY-2000 is spinning at 650 RPM. That last 100 RPM makes a big difference in power output. 1000 watts is a lot! The factory said that the HY-2000 is safe to a maximum speed of 800 RPM. So, if I could limit it to 650 RPM and still get 3kW out of it, then that would be great. There would be a good safety margin for wind tubine RPM, and I'd still get some good power at higher winds. Right now, with this MOSFET controller, I am throwing away 1kW by limiting RPM to 550 RPM and 40.0A output. The other turbine that this controller was made for did need to be limited in speed to a lower RPM. My HY-2000 can take much higher RPMs safely.

I still have my eye on the Midnite Solar Classic MPPT controller for wind. Time will tell what happens.

Edward

MisterB

Re: Classic/Clipper MPPT Wind Turbine Controller

keyturbocars wrote: »

Today, we had some stronger winds that were peaking in the 30mph range, so I was able to do some more testing on this MOSFET controller. This is what I found out. The controller circuit is programmed to limit power output to 40.0A (very precisely). When power hits 40.0A, then the circuit pulses the MOSFET gates and loads down the turbine with the 4kW resistor heating elements. This continues as long as the wind is strong and holds the max power output to 40.0A (2kW). I like this safety feature of the electromagnetic braking, but the limit on this other controller is set too low for my HY-2000 turbine.

With the other controller that came with the HY-2000, I would have been seeing 60A surges during the 30+mph winds. I've seen as high as 65A surges before. Now, too much of a good thing can be bad, which is why I'm looking into using this other controller. I am now investigating if there is a way to change the power limit on this controller when the electromagnetic braking takes effect. If I could change it from 40.0A (2kW) to 60.0A (3kW), then I could take full advantage of the power available, but still have the safety of electromagnetic braking.


Edward

If it is sensing and measuring current, there should be some sort of shunt in the controller. I don't see any obvious shunts in the pictures but if there is a current meter on it, it you should be able to find the shunt by tracing the wires from the meter and the voltage accross the shunt will be more than likely what the controller is using to know that the current has reached 40 amps. It looks like there is something like a Pic microcontroller on the circuit board which is what my controller has, and the current trip point and curent limit could well be set in firmware which makes changing them difficult but if there is a shunt circuit used in measuring current, it would be possible to fool the sensor circuit by puting an isolated voltage divider circuit between the shunt and sensor which would feed the sensor a lower voltage for a given current which would mean the controller wouldn't start dumping until a higher current was reached.

See what happens when you add more mosfets which will raise the capacity of the controller to 3kw. If the firmware is really well written, it might adjust automatically to a 3kw configuration. If not, the first step is to figure out where and how it is reading current.

I just looked at the picture again and noticed what could well be a shunt on one side of the rectifier. I see the 3 phase input on the right side with positive and negative outputs in the middle and what looks like a shunt on the left side connected to the positve contact in the middle. Check the continuity between the point where the short red wire is connected on one side and the middle contact with the long red cable running off of it. The more I look at the rectifier block the more the left side of it looks like a shunt to me. There are 2 small cables running from the top and middle contact point to the controller board which is what I would expect if the controller is measuring current.

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

MisterB, you are right that it looks very much like a shunt. That is actually a diode for the solar input into the controller. This controller allows solar and wind input. I agree that it seems that there has to be a shunt somewhere in order for it to be able to monitor current, but there is no traditional shunt in this controller. It appears that the IC chip calculates the current based on voltage drop across a current sense resistor. I am not 100% sure on this though.

The digital display on the controller shows current ouput, and I checked it's accuracy with an external analog ammeter that I wired in for testing. The analog ammeter I used has an internal shunt. So, the circuit is accurately calculating the current somehow as verified by the analog ammeter.

MisterB

Re: Classic/Clipper MPPT Wind Turbine Controller

The only other way to measure DC current that I know of is the Hall effect which is what my clamp on DC ammeter uses. Here is what Wikipedia has to say about it:

http://en.wikipedia.org/wiki/Hall_effect

In DC mode, my ammeter has to be constantly re zeroed and the readings are accurate only for a couple of minutes. In AC mode, it self calibrates to zero. This doesn't look like a good way to put a stable current meter in a controller and I don't see anything around any of the cables that looks like a magnetic current sensor so I'm baffled on how this controller is measuring current.

keyturbocars

Re: Classic/Clipper MPPT Wind Turbine Controller

MisterB, I didn't even know this until recently, but apparently a circuit can calculate the current by simply measuring the voltage drop across a known resistor. The "resistor" can be an actual current sense resistor, or a trace on the board with a known resistance, or a wire.

niel

Re: Classic/Clipper MPPT Wind Turbine Controller

keyturbocars wrote: »

MisterB, I didn't even know this until recently, but apparently a circuit can calculate the current by simply measuring the voltage drop across a known resistor. The "resistor" can be an actual current sense resistor, or a trace on the board with a known resistance, or a wire.

the shunts you see available for meters are those resistances. very low in resistance and high power capability with nearly no heat noticeable due to it being large areas of metal.