Wind turbine brake control

[Islander71]

I have an early Iskra 5Kw wind turbine now about 17 years old. The company was taken over at least twice, and the present company currently appear to have no information or parts for these machines, and all the people who designed it have long retired.. The blades are speed controlled by the blades twisting (rotating ) to spill wind. The spring loading can be adjusted to give the designed rotor speed, which before the invertors kick in loading the generator should give a voltage of 410-470v with the blades feathering. This all works fine with it currently feathering out at 430v. There is an complicated electronic brake control device which shorts the 3-phase generator output into braking coils should it overspeed. This can also be triggered by a switch with 2 x 9v batteries at the base of the 12m tower to manually stop it. The original brake control unit failed at 11 years and a special one-off brake unit was built for it by the original Iskra electronics engineer. It also stores the data as to why the brake operated which can be de-cyphered by a series of sound beeps.
This unit from the start was overly sensitive to sudden gusts of wind shutting it down in gusty but not high wind conditions. I got steadily worse until I replaced the 2 "impulse relay units" with the 2 from the old brake unit, which enabled it to run with de-tensioning the pitching springs to give a reduced output of 3.7Kw. With this it only occasionally shut down for no good reason. At its recent service I increased it to the rated speed so it now gives a max of 4.7Kw, but the brake is coming on frequently at fairly steady wind speeds below its full speed - the turbine is running steadily at maybe about 4 Kw when it will just suddenly brake.
These are the 2 impulse relays - Finders 20.22.9.012 - https://www.digikey.co.uk/en/products/detail/finder-relays-inc/20-22-9-012-0000/10055779?utm_adgroup=&utm_source=google&utm_medium=cpc&utm_campaign=Dynamic Search_EN_Product&
I have no knowledge of electronics, but wonder if I could replace the 2 relays with less sensitive ones, does this sound feasible? If so could anyone suggest suitable relays. Or is there anything else I could do?

The The only other option I can see is to disconnect the brake coils and hope it doesn't overspeed and destroy itself!
f.

 

[Erie Fred]

sounds like you want a time delay ahead of the brake applying relay ?
Set at 5-15 seconds, when the "call comes in" of an overspeed, it starts
timing, and if still at "overspeed" after 5-15 seconds, it then trips the original relay.

 

[Islander71]

sounds like you want a time delay ahead of the brake applying relay ?
Set at 5-15 seconds, when the "call comes in" of an overspeed, it starts
timing, and if still at "overspeed" after 5-15 seconds, it then trips the original relay.

That sounds like it might work, though I think it is applying the brake at any sudden increase in speed rather than at overspeed. I'm not sure how I would I could fit such a device, are they available off the shelf?

 

[Agroshield]

It is a little difficult to see what you mean by 'sensitive relays'. The ones to which you link are nothing special. They have no smartness, no sensitivity, no special spidey senses. Relays are very passive components: they do what they are told. When they receive a control signal (which could come from a timer module), they trigger. In focussing on the relays, I would suggest that you could be looking in the wrong place.

There is some other part of the control circuitry that monitors the speed (?) / output (?) and once it reaches a pre-determined level, sends a signal to trigger the relays. It appears to me that this is the item that is maladjusted, broken or misbehaving.

The timer suggested above is a good idea and might stop the problem occurring but does not address the cause of the problem. In a way it is like putting a bucket under a leaking pipe rather than fixing the pipe itself.

I might be talking through my hat here, but AIUI, capacitors are often used as filters in circuits, to dampen out spikes/variations. If the system is old, some of the capacitors may have gone bad and are allowing false triggering of the relays. Hence, I would check every capacitor for physical distress as a start and then perhaps replace them with new items (caps are difficult to test in circuit).

 

[Erie Fred]

Yup ^^^ I'm wondering if they have a largish capacitor (with bleed resistor) used as a slugging circuit.

 

[minimutly]

Google charge pump circuit - quite simply the pulses are rectified and charge a capacitor, pulse by pulse. The other bit of the circuit is a discharging resistor which continiously bleeds off some of the charge - lots of pulses mean a higher dc voltage at the capacitor. Then all you need is an electronically triggered relay, a resistor, potentiometer and a zener diode to set the switch on point of the relay. Easier than it sounds

 

[Islander71]

Here is a photo of the original brake unit dismantled to get to the relays. There are a couple of quite large capacitors. Would increasing their capacity in the new unit help?

 

[Islander71]

As I said earlier my knowledge of electronics is minimal. The wind generator produces 3-phase AC electric at quite high voltage up to 370V, so I guess each phase about 125V. I am assuming the brake control works by reducing and rectifying the tapped off voltage, so that if the generator exceeds a set limit - maybe 490V - it produces enough voltage through the electronic wizardry to activate the relay which looks to need about 12V 5W to trip. Does this sound right? If so would putting in a relay that say needs 15 or 18V to trip de-sensitise it? If so, are they available?

 

[Agroshield]

Would increasing their capacity in the new unit help?

Yes, no, maybe.

I am not sure why you are keen to change things. It worked before in the past. It was designed and specified by a proper electronics control engineer in the past.

A load of amateurs speculating over it on a forum is not going to improve it.

If you fiddle with it at all, replace like-for-like.

If it were an IC engine, you are not aiming to tune it, but to blueprint it.

Do a BigClive on it and reverse engineer and draw out the circuitry. That would educate you and us on how it actually works and allow some SWAguessing rather than the entrail-consultation or tea leaf patterns we are currently engaged in.

 

[gaz1]

since you have the old one draw a diagram of its wiring

you can also rebuild the old circuit board as well before you even touch the new failing model as you have now

 

[Islander71]

Yes, no, maybe.

I am not sure why you are keen to change things. It worked before in the past. It was designed and specified by a proper electronics control engineer in the past.

A load of amateurs speculating over it on a forum is not going to improve it.

If you fiddle with it at all, replace like-for-like.

If it were an IC engine, you are not aiming to tune it, but to blueprint it.

Do a BigClive on it and reverse engineer and draw out the circuitry. That would educate you and us on how it actually works and allow some SWAguessing rather than the entrail-consultation or tea leaf patterns we are currently engaged in.

The original brake unit did seem to work, although it never switched off even in severe storms. After it stopped working at all, the people at the revamped turbine company had no record of the original design, their new turbine braking system was different, so their electronics engineer who knew the earlier designed turbine designed and built a new one-of unit for me. Unfortunately from the start it was oversensitive and kept cutting out.. I did complain, but it had been built as a personal favour as the original company had gone bankrupt and been taken over, and he insisted it must be the turbine over speeding, even when it wasn't. I could only partly cure it by reducing the speed and output of the turbine, which was hardly ideal. I could limit the speed and output again, but I would prefer to alter the brake so that it worked properly at the designed power output.

 

[Gareth J]

Coincidence, was just servicing ours today/yesterday!

I know ours is a later one, that you've found works differently - the 2x9v battery box at the base of the tower isn't what's photoed there, is it? That must be the box that lives at the top. I've never opened ours but, if it helps, next time I lower it (hopefully next summer) I'll take some details.

One thing, I've never had the brake come on while the pitch bearings were working correctly. Only when they've got tired.

Are there any potentiometers in the box? Maybe whoever designed it built in a bit of adjustment but that information got lost.

On a tangent - have you got any leading edge repair suggestions? Body filler and lacquer doesn't seem to work for a year.

 

[Erie Fred]

On a tangent - have you got any leading edge repair suggestions? Body filler and lacquer doesn't seem to work for a year.

There is a stainless steel tape used on Ivo & other ultralight airplane propellers leading edge.

Steel Leading Edge Prop Tape | Aircraft Spruce

Steel Leading Edge Prop Tape This part replaces the leading edge tape on the Ivoprop.

www.aircraftspruce.com

 

[500e]

3M do a plastic self adhesive tape for helicopter blade's to stop erosion, it is expensive and has limited shelf life.
How much do you need ?
Will see if we have some coming up to date, it still sticks like

 

[minimutly]

Yes, no, maybe.

I am not sure why you are keen to change things. It worked before in the past. It was designed and specified by a proper electronics control engineer in the past.

A load of amateurs speculating over it on a forum is not going to improve it.

If you fiddle with it at all, replace like-for-like.

If it were an IC engine, you are not aiming to tune it, but to blueprint it.

Do a BigClive on it and reverse engineer and draw out the circuitry. That would educate you and us on how it actually works and allow some SWAguessing rather than the entrail-consultation or tea leaf patterns we are currently engaged in.

No, it never worked I think is how I read it. I suspect it probably was a simple diode pump that needs setting up

 

[Gareth J]

If the current box does what it's supposed to, but just at too low an input voltage, and there's no adjustment built in, maybe you can fudge adjustment yourself without touching the setup they have or knowing exactly how it works.

If you could solder in something with an amount of adjustment that would reduce the input voltage by a bit, the current box should operate properly?

A potentiometer? (I also don't know enough about electrics to be confident here)

Risk of your added componentry failing open circuit should be considered too

3M do a plastic self adhesive tape for helicopter blade's to stop erosion, it is expensive and has limited shelf life.
How much do you need ?
Will see if we have some coming up to date, it still sticks like

Some kind of tape sounds great in terms of installation but I don't know if it would be any good around the tips, which have a pretty compound profile....? Blades are about 3m long but the last 0.5m gets all the hammering. X3blades so even 1-2m total would be enough I'm sure.

That said, I'll need to take the blades off next year anyway to do another repair, so could attempt something more appropriate then.

 

[500e]

The tape will not go round compound curves.
Never tried cutting as all our use is strait runs and wrap round leading edge
The 500 blades are running at high fps

 

[Brad93]

As said relays are just relays.

There must be a board or control circuit which monitors rotor speed and tells the braking circuit to act

 

[Neilj]

There are two small preset potentiometers on that board (circled in red) that are sealed with white paint. One of them is likely to be your trigger point adjustment. However, just adjusting them blindly isn't going to help, an understanding of the circuit and some testing would be needed to determine the setting.

 

[Islander71]

Here is a better photo of the original brake box, I dont have one of the new brake box which is different and its a major operation to get the turbine lowered and raised to photo it. The turbine head is about 1/2 ton on the end of a 12m steel pole and lowered and raised painfully slowly with a 2.6t Tirfor type hand winch via a gin-pole to get a bit of an angle on the pull. At 75, its now about the limit of my strength to initially raise it. Could do with a powered Tirfor winch!
At the top left are the 3 generator wires then the 3 wires to the brake shorting coils. The 2 wires at the bottom are from the brake setting switch at the bottom of the tower.
The brake setting switch is 3 position. It can be held against an inbuilt spring to change the brake to run or stop, which after a short while you can hear the buzz of the relay activating, it is then pushed back to set that, or pushed to the mid position to test the auto braking, which then activates at low speed. Within the brake switch are 2 x 9v PP3 batteries.

Thinking about it last night, I thought maybe there could be dampness in the switch box causing some voltage to track over the switch, setting off the brake, so this morning I restarted the turbine with the switch, then disconnected the 2 wires from it, so there could be nothing going up from the switch box to the brake box. I was mighty surprised by the result! Within a couple of seconds the brake operated - it had been activating anything from a few minutes to a couple of hours after a re-set. Thinking perhaps I'd paused a moment in the mid position before dis-connecting, I did it again with exactly the same effect. So it appears the switch does not just send some current to trigger the relay when its pushed, but must supply voltage up to the brake unit constantly and if this gets too low the brake activates. Must be a safety feature I guess so that you can always turn it off or it will do it itself if the batteries get low!
I was going to replace the 2 batteries in case they are getting low - they have been in there for a couple of years I think, but after reconnecting the 2 plugs and switching on, its been running constantly for the last few hours. Maybe a poor connection in one of the plugs? If it stops again I'll replace the batteries and see what the output is in each of the 3 positions.