Clippers, Resistors & Burned Slip Rings

Started by devo, December 21, 2013, 09:02:35 PM

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devo

Hey everyone!

I'm back to this great forum to look for some insight into our latest issue in off-grid energy generation. For a bit of background we are using Classics and Clippers at our remote telecom sites to power our equipment. The solar has been working great, although we don't have much sun this time of year. The wind systems haven't been going so well. The turbine is a HYEnergy HY-1500 tied to a 4KW AC Clipper at 1.6 ohms per phase, controlled by a Classic 250. The battery bank is 530 Ah @ 48v.

About a month ago we discovered that our new HY-1500 wind turbine wasn't producing any power. After a few discussions with Ryan and boB we came to the conclusion that the turbine was the problem, and not the classic/clipper. We removed the turbine from the tower and replaced it with another new one. Things were going great until a few days ago when we visited the site and realized the same problem had appeared again.

Thinking it was simply a faulty turbine, we didn't take the time to determine the true problem the first time (big mistake). After the second unit showed the same symptoms, we disassembled the first toasted turbine to find the slip ring badly burned.

Here's what we found:





As you can see, two of the phases shorted together and burned the plastic, as well as pitting the shaft and depositing carbon on the copper. While i'm not a fan of the plastic separator between the brushes, it would seem that a substantial amount of current was dissipated on the slip ring.

Now, for the million dollar question: what could possibly cause this to happen?

Our current theory is that there isn't enough load on the system and the classic is telling the clipper to stop the turbine quite often in very high winds due to the battery bank being in float. This constant start-stop of the turbine in high winds is creating some sort of arcing on the slip ring causing it to burn and eventually completely short. To compound the issue, we (and boB) believe the resistance, 1.6 Ohms per phase, is too low. When the classic tells the clipper to slow/stop the turbine there is a huge amount of current going through the slip ring.

Does this sound plausible? Or am I completely out in left field?

Does anyone have a HY-1500 or HY-2000 operating on a clipper, and if so, what resistance per phase are you using?

When the turbine was operating normally we have seen over 2500 watts being pushed through the classic. Winds at this site regularly hit over 100 Km/h or 60Mph and can gust to nearly 180 Km/h multiple times per year, especially now. During normal operation we have never had any heat coming from the clipper and have never seen the fan turn on.

Anyone have any ideas or comments? We're open to any suggestions!

Thanks

boB

Devo, I didn't know you were this person !  This is great that you have brought this to the forum.
There are lots of good heads on here !

So, we ~think~ that part of the problem may be that the clipper is engaging when there is a LOT of
inertial stored up in that HY1500 turbine and sending too much current through the slip-rings.
I know you have VERY high winds up on that mountain.  (120+ MPH I think you said)...

So, you have a 4kW AC Clipper and it is a 1.6 Ohm, meaning that there are 6 resistors, 2 in series
and each one is 0.8 Ohms.   I was going to say to place them in series to increase the resistance
but can't just do that because they're  in series already.

SO, you COULD just remove one wire of each 1.6 Ohm resistor and then add another power resistor
in series with each one of those to reduce the current.  You of course have to be careful not to go TOO
high or else it won't clip... BUT, you can certainly experiment slowly by gradually adding some resistance.

Question is, do you have anything you could try ?

Another idea is to reduce the fail-safe clipping voltage in the clipper to a much lower
value so then there isn't so much power available when it does clip.  RPMs of the Clipper will
be much lower too.  If the wind power curve you are using is the same as the HY2000 curve,
then the highest voltage is 120V DC.  So try bringing the absolute highest clipper voltage down
to around, say, 140 volts or so (a bit of headroom).

Another idea, which we talked briefly about was to add some battery side diversion.  You could
do this with Aux 1 and keep the Aux 2 for the main Clipper drive signal.
The best mode for this Aux 1 might be the Waste-Not mode.  This will, instead of the Classic
raising its input voltage (turbine RPM and voltage) in Absorb or Float to regulate the voltage,
keep the battery voltage down using the external diversion load.  When doing this, you set
the Waste-Not relative voltage  at minus 1 or 2 volts.  Then, raise the Absorb and Float set-
point voltages a volt or so.  When the battery side diversion doesn't work,  the Classic will
then raise its input voltage (the turbine voltage) to reduce the battery voltage and then
the Clipper will come into play.  That's the fail-safe.

So there are more than one way of skinning this cat but you will still need more power
resistors, either for the Clipper or for the battery side diversion load.

More comments welcome and still thinking about this.

There is also another user here that has a HY2000 and AC clipper (Turbokeys) but I highly
doubt he has nearly as much wind as you have.

How about these guys here ???    http://www.wimp.com/antarcticaweather/

boB
K7IQ 🌛  He/She/Me

dgd

#2
When the battery bank is at Float then why bother with the wind turbine? You obviously don't need the current from it.
Turn off the turbine using a Contactor enabled by AUX1 Float High to short out the three phases. Better in shutdown mode rather than trying to use the Clipper to keep the turbine loaded, especially in those high wind conditions you have. ( just IMHO  :))
dgd
Classic 250, 150,  20 140w, 6 250w PVs, 2Kw turbine, MN ac Clipper, Epanel/MNdc, Trace SW3024E (1997), Century 1050Ah 24V FLA (1999). Arduino power monitoring and web server.  Off grid since 4/2000
West Auckland, New Zealand

devo

boB & dgd - Thanks for the replies! boB you actually spoke with John, I'm Devin, one of the other business partners. John has the electronics background and helps with these sorts of issues. I mainly deal with the tower and site construction aspects. When you spoke with him we were in the midst of the office Christmas party!

I think issues like this can certainly help build the community knowledge base and perhaps someone else who may be experiencing a similar problem. Wind turbines are great when the work, but are very difficult to get right.

We do have a couple of other 4Kw clippers at the office, perhaps we can use the resistors from one of those to test out the theory. It might not look pretty, but it would tell us if additional resistance would soften the slowing of the turbine. Before the last failure, when the clipper would engage the turbine would come to a screeching halt. If I had to guess I would say it would spin up to 200 RPM and then when the clipper would turn on the turbine would instantly stop - not slow down. It was almost like the turbine was shorted.

If we take an additional resistor bank and put it in series with the existing one we could double the resistance and see how that works.

For the Aux1 suggestion we were actually on site to add a 250w heater to the system when we discovered the turbine problem. This will be completed when we replace the turbine on the next trip. It should help use some of the excess power we're generating at the moment as you suggested. We have a half dozen other heaters at the office, so if one doesn't work, we can turn the equipment shelter into a tropical resort!

@dgd - Right now we don't have much load on the system at all. I would estimate around 1 amp constant draw. Over the next few months we will be adding the majority of the radio equipment and increasing the load dramatically. We wanted to have the turbine and solar systems operating for a while to look for problems just like the ones we've been experiencing. Once the final radio equipment is installed and the network is running, any interruption in power would result in multiple communities losing internet and data services. That's a lot of phone calls!

boB the condition 1 in Antarctica is pretty similar to the conditions we face - perhaps not quite that bad though! A student at Memorial University here in Newfoundland did a thesis on small wind turbines used for telecommunications sites back in 2009: www.engr.mun.ca/~sbruneau/research/windresearch/jrthesis.pdf‎

It's an interesting read. Aliant, the largest telecom company in the region, could not maintain small wind turbines (Whisper 100's) at their remote sites. The incredible wind speeds and gust forces actually snapped the turbines in two at the mechanical furling mechanism. While the area of study is quite a distance from our operation, conditions are very similar. On the last visit we had over an inch of glaze ice on the tower. In Labrador, towers can accumulate up to a metre or more of rime ice!

For this reason we have tried to find a turbine that has no electronics in the nacelle whatsoever. Just a standard 3 phase pma. We also didn't want mechanical furling due to the problems Aliant faced with them. We settled on the HYEnergy turbines for these reasons, and because they were relatively cheap to test with. I wouldn't want to blow up two or three 1.5Kw Kestrels for the sake of testing!


Westbranch

Devo, that link does not work  404 error?

Got to this page:
www.engr.mun.ca/~sbruneau/research/windresearch/

KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 FW V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

TomW

I have to agree with DGD here.

In my experience it is far better to just shut down the turbine in high winds if power is not needed. Might be a hard current surge while activating the braking but most turbines will not get any speed up while shorted so the blades are stalled and unable to produce enough lift to get moving very fast.

Seems much better than intermittently loading it and letting it fly hard?

No expert but been flying turbines a few years.

Good luck with it.

Tom
Do NOT mistake me for any kind of "expert".

( ͡° ͜ʖ ͡°)


24 Trina 310 watt modules, SMA SunnyBoy 7.7 KW Grid Tie inverter.

I thought that they were angels, but much to my surprise, We climbed aboard their starship and headed for the skies

devo

TomW - Thanks for your input. We won't be able to shut down each and every turbine in high wind events. Right now we have 7 sites running with turbines, all in different areas. Most of those sites are on remote mountaintops and hard to reach even in summer. The only way we could possibly do it would be with some sort of control system based on actual wind speed.

While we do not need the power right now, we will in the coming months. We would also like to ensure that the clipper can control the turbine without any manual intervention. Discovering this problem now is much better than having it happen on a live site!

Westbranch - The link doesn't seem to work, but the url was right. You're link works better. Thanks.

Is there some setting on the classic that determines when to allow the turbine to spin up? For example if the battery bank goes into float, let it fall to X Volts before allowing the turbine to start up. Maybe we can prevent cycling the turbine on-off when the battery bank is close to full?

Westbranch

Quote from: devo on December 22, 2013, 01:41:12 PM

For example if the battery bank goes into float, let it fall to X Volts before allowing the turbine to start up. Maybe we can prevent cycling the turbine on-off when the battery bank is close to full?

That sounds like a job for the WhizBang Jr...???
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 FW V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

dgd

#8
Devo,
This slip ring burnout looks like high voltage/high current arcing to the shaft (at earth potential). The reason for this,  I would speculate, is a runaway turbine, in high winds, without any effective braking.
I looked at the HY-1500 specs and I see there is no mechanical, ie tail furling, overspeed protection.
According to their web site -
Over-speed control - Electromagnetic & blade aerodynamic braking
The electromagnetic  would appear to mean that the turbines 3 phases are shorted together. I cannot see any electronics to do this in the turbine body so it would appear to happen in the HY hybrid controller/inverter they want you to use with the HY-1500
The blade aerodynamic braking is interesting, the design does not look complex enough to have some form of proper blade feathering so I guess it must be torsional twisting of the blades that deforms them and hence they become inefficient and slow the turbine - and probably screech to waken the dead too - something like the swwp Air303 used to do  :o

One thing I noticed you said in your original post was that you normally seen over 2500 watts being pushed through the Classic. That, from a rated 1500W turbine with 1800 watt max, certainly seems to show a turbine routinely running way over its design speed.
Although I must admit being surprised that a swept area of about 3.2sqM could extract over 2500 watts but I suppose at 70mph+ winds  :-\

So what has happened to the braking?
The blade braking appears ineffective and if you are not using the HY controller then it appears there is no electromagnetic braking either.
SO the Clipper should be taking over the electrmagnetic braking function. It would appear to be NOT actually doing that otherwise you would be seeing the resistor bank heating up and the input to the Classic dropping back.
I don't undertand how the Clipper is just bringing the turbine to a dead halt. If the AUX2 in the Classic is wired to the Clipper with Clipper control setting and AC type PWM then the Clipper should be gradually introducing the resistor bank and slowing the turbine, NOT just bringing it to a dead halt.

I assume you have check all this is wired up as its supposed to be?

My personal thoughts on this configuration you have are that I would not use a turbine such as the HY-1500 at a remote unattended location.
No failsafe mechanical protection such as some form of furling or feathering would concern me about storm/high wind conditions with a runaway and burning up turbine.
The manufacturers web site specs for the HY-1500 describe it as a 'low wind startup' 5 blade design and goes on to show it in commercial use with a 300w PV to drive an almighty load of four 50W led street lights - which obviously on come on at night!

I agree the Clipper resistance may be too low. In tuning my Clipper with 48v 1.5Kw turbine, also a Chinese model but 3 blade, max 2100watts, nice big tail on heavy boom and furls real smoothe, I reconfigured the resistance with 1.3 ohm 1000W types.

Finally I followed ChrisO's advice in why have the turbine/Clipper loaded when you don't need it? When batteries are in float. That was the reason for using AUX1 on a contactor or decent SSR to turn off the turbine by shorting out the 3 phases via the contactor/relay.

One other advantage of this is that if the weather forecast tells you of storm conditions at one of your sites then you simply log into the Classic and set AUX1 to ON which enable the contactor/SSR and effectively turns off the turbine.

dgd


Classic 250, 150,  20 140w, 6 250w PVs, 2Kw turbine, MN ac Clipper, Epanel/MNdc, Trace SW3024E (1997), Century 1050Ah 24V FLA (1999). Arduino power monitoring and web server.  Off grid since 4/2000
West Auckland, New Zealand

TomW

Quote from: devo on December 22, 2013, 01:41:12 PM
TomW - Thanks for your input. We won't be able to shut down each and every turbine in high wind events. Right now we have 7 sites running with turbines, all in different areas. Most of those sites are on remote mountaintops and hard to reach even in summer. The only way we could possibly do it would be with some sort of control system based on actual wind speed.

While we do not need the power right now, we will in the coming months. We would also like to ensure that the clipper can control the turbine without any manual intervention. Discovering this problem now is much better than having it happen on a live site!

Westbranch - The link doesn't seem to work, but the url was right. You're link works better. Thanks.

Is there some setting on the classic that determines when to allow the turbine to spin up? For example if the battery bank goes into float, let it fall to X Volts before allowing the turbine to start up. Maybe we can prevent cycling the turbine on-off when the battery bank is close to full?

Devo;

Pretty sure the Classic can do that automatically by using the AUX 1 per DGD's suggestion:
Quote
Turn off the turbine using a Contactor enabled by AUX1 Float High to short out the three phases.
The Classic can do this shutdown automatically which means you don't have to be there to do it.

Tom
Do NOT mistake me for any kind of "expert".

( ͡° ͜ʖ ͡°)


24 Trina 310 watt modules, SMA SunnyBoy 7.7 KW Grid Tie inverter.

I thought that they were angels, but much to my surprise, We climbed aboard their starship and headed for the skies

devo

dgd

We don't normally see 2500 watts, but in normal operations we have seen 2500 watts. I just looked at the offline data from the controller and it shows over 2.5Kw of peak power on two occasions, with 1.5Kw on two other days and the rest were well under 1Kw. The highest Vin the controller saw was 142.5v when the turbine was producing 1.5Kw. The last day it produced power the turbine's peak was 136w.

I agree that this turbine isn't the right fit for this area. We need a three blade turbine instead of a five. I'm not convinced a mechanical furling mechanism is good though - I'm not sure it would last.

Like you, I think the braking is causing the issue. It's just a pure guess on my part, but it seems like there is just too much amperage being put through the slip ring when the clipper tries to slow it down. This is why we are looking at the resistance value and trying to determine if it is too low. We've checked the wiring and settings a bunch of times. We even replaced the clipper with another one to see if that was the issue.

Is it possible that the 4Kw load is too large, causing the turbine to basically short instead of slow? A higher resistance would reduce the amount of amperage coming through. You're using 1.3 Ohm's per phase or you rewired it higher? How high should we go for testing? I was thinking of going to 4 Ohms per phase to see how the turbine reacts.

The only other option we've looked at is removing the clipper and going to a full diversion load - i.e. keep the turbine completely loaded at all times. All of our other sites run this way and we have not had a single issue in the 18 months or so they have been running. Granted, this is the first time we have tried a turbine this large. The other sites use 600w units.

I think the blade deformation thing is just to prevent the turbine from physically coming apart. It may prevent the blades from coming off, but I don't think its something I want to try!

Thanks for your valuable input. We'd like to come up with some possible solutions and folks like you are a great help!




boB

#11
I do not think you want to unload that turbine in such a windy site, even if you don't need the power at that time.

First, when is it going to slow down enough to reconnect and second, is it going to fly apart when it is free-wheeling
in such wind ?  I don't know if the HY can handle being unloaded in such a case.  Maybe, maybe not.

Also, getting 2500 watts out of a 1500 watt turbine is usually just fine.  That's why MPPT for wind is so
cool.  Let it spin faster but not "too" fast.

As I emailed John today, it may be that the fail-safe on the Clipper is turning on at a lower voltage
than the Classic's Aux 2 is commanding it to be on.  The Clipper's fail-safe clipping function is
not PWM and may very well seem like a brake being slammed on.  PWMing from AUX 2 is better
when it can be used.  Aux 1, which is not as high of frequency PWM is good to use for battery
side diversion control in addition to the AUX 2 PWM SSR/Clipping control.

For completeness here, I will copy and paste some of the email I sent to John a few minutes ago...

boB

****************************************************************************

The Clipper is not supposed to jam on the brakes, but maybe the setting is not right ?
Are you using AUX 2 ?  Aux 2 should be more of a higher frequency PWM control.

Now, if your Clipper is doing all off the clipping because maybe its trim-pot is set
for a lower voltage than the Classic is trying to keep it down to, then maybe that
is the problem ?   This would be because the Clipper fail-safe voltage trigger is
not a PWM control, but it leaves the triac SSR on longer.  I wonder if this might
be the problem ?  Next time you are up there, turn up that trim-pot on the Clipper
itself while the Classic is connected and Aux 2 is controlling the Clipper.
Remember that the Clipper AND the Classic can make it clip but the Classic
Aux 2 output actually drives the SSR itself with the internal fail-safe control
of the Clipper "OR'd" with it so if for some reason the Classic doesn't catch it,
the Clipper will.  The Clipper should be adjusted to the highest voltage you need.
It can even be set for around 300 volts for a Classic 250 or 250 volts for a Classic
200 but the Classic will not turn on (make power) until the wind dies down to below
250V or 200V.

You can try the Classic's Aux 2 clipper mode or the Aux 2's PV ON HIGH mode.

The Classic Clipper Aux 2 mode also has a high voltage maximum adjustment in
addition to the Clipper mode itself which tries to keep the turbine clipped to just
above what is necessary to keep the Classic in Absorb or Float (voltage regulation)
or even EQ mode.

OK, so if this is NOT the problem (Clipper fail-safe) then it must be that the
clipper resistance is WAY WAY too LOW and needs to be raised.  I would first
question the Clipper's fail-safe operation and its adjustment because that sounds
more like what is happening to me.  Shorter, PWM pulsing will be a lot more
graceful, but if it is just turned ON for a few seconds, will seem like slamming
of the brakes.  That might be OK once in a while, but if it can be PWM'd, then
should be much smoother.

boB
K7IQ 🌛  He/She/Me

boB

OK, John and Devo have their Classic adjusted correctly I would say.

Let's see if we can keep it from clipping so much.  Here's a couple more ideas.

I will say that since the input voltage can be less than even 150 volts that
the Classic might actually want to be a 200 or a 150 which will allow more
output current (power) and then battery side diversion can be added to
help keep the system from clipping so much, or maybe at all.

The output current is set at 50 amps and 2500 watts at at 50 volts is
55 amps.  I have a feeling that if the output current is set to more like
80 amps, the battery side diversion will help a lot.

Another thing that will need to be done if battery side diversion is
used, (or maybe not ?), is to adjust the power curve.

In fact, something that we did recently on a 250 connected to a hydro
turbine (24V battery) that was putting out too much power and clipping too
much, was to actually bring the power curve voltages down for a given
output current.

This power curve "de-tuning" can actually be used to help stall the
wind turbine at these higher powers since there you are getting more
power than you need anyway.   Sort of a compromise between
direct connected and full MPPT....

It may be a simple matter that it is working too well.

Captain !  She can't take much more !

boB
K7IQ 🌛  He/She/Me

boB

To "de-tune" the curve, try keeping the cut-in voltage the same as it is.

Turn up the highest curve output current and turn the voltages down.

Not sure where to start exactly, but maybe somewhere around 1/2 way up
the curve and continu all the way  up to the very top.

boB
K7IQ 🌛  He/She/Me

RossW

Quote from: boB on December 22, 2013, 07:51:41 PM
OK, so if this is NOT the problem (Clipper fail-safe) then it must be that the
clipper resistance is WAY WAY too high and needs to be raised.

Guessing that was meant to be WAY WAY too low and needs to be raised.
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