Windturbine Alternator Vibration in Absorb & Float

[Boondocker]

Hello,

I'm using a Classic 150, with a AC Clipper, on a wind turbine.  The wind turbine is a version of Dairy Land design running on a 24v battery bank.   http://www.fieldlines.com/index.php/topic,147743.0.html

When the control changes from Bulk MPPT to Absorb, the turbine alternator will vibrate continuously.  The vibration will stop when the control returns to back into Bulk MPPT.    The alternator vibration remains in Float state also. Is there a way to make the alternator run as smooth as it does in Bulk MPPT?

This vibration, and resulting tower resonating noise,  has been present from the maiden raising.  All of the fittings are tight on the alternator.

Thank you,

Boondocker

[dgd]

Hi Boondocker,

So it would appear that the turbine is not liking the transition of the Classic from BulkMPPT state.

The Classic will be enabling the CLIPPER CONTROL pwm signaling via AUX2 that is input to the Clipper which in turn is introducing the three resistors (or whatever you have) into the AC lines from the turbine.
My first thoughts on this are that if the resistor values are too low then probably no matter the pwm rate the pulsing of a near short over the AC lines will be causing the turbine to brake/run at a frequency causing the vibration you hear.

If the turbine is making power and the Classic in in BulkMPPT mode and you use the run/stop switch on the Clipper to STOP the turbine then wht happens to the turbine?
Does it halt pretty quickly? or is there is a time, several to tens of minutes for the turbine to slow to a halt? or does the turbine slow but not actually stop?
And during any of this time does the turbine make the vibrating sound?

What value resistors are in the Clipper? How did you calculate what value resistors to specify for the Clipper?
How long are the 3phase AC lines from the turbine to the Clipper? and wire gauge?

re: otherpower - nice turbine construction, its been vibrating for a couple of years now or is this more recent? getting worse? Do the Clipper resistors look as though they have been running hot?

dgd

[Boondocker]

Hi Dgd,

Thank you for responding. 

The vibration has been there from the start.   The Clipper resistors are not running particularly hot.  There is some warmth being vented from the top.  When placing my hand over the vents,  its about the same has a warm mug of coffee; but not hot.  I've never have noticed the internal cooling fans to turn on inside the clipper.

The wire run is approximately 100'  of 10 gauge wire down the tower where it terminated to 6 gauge wire for another 90'  to the clipper. The Clipper was ordered with 1.6 ohms resistors.  At the time, the resistors were recommended based on the turbine capacity produce 1400 watts.  No resistor calculations were performed.

The turbine stops very abruptly  when the alternator AC lines are shorted using the Clipper shutdown switch.   I'm 100% sure if the vibration occurs when alternator is shorted.  The shutdown it occurs very quickly.  I'll report back.

An observation: The vibration will occur before AUX2 signal comes up on the Classic display.     For example, the turbine will producing power between 50 and 300 watts in Bulk MPPT.  The breeze stiffens, output climbs to 350 watts, and the controller goes into Absorb.   As long as the wind stays up (and stronger), the output remains at 350 watts.  Only in a really good puff of wind will I see the AUX2 signal pop-up on the display.  Note: the values provide above will change with the battery SOC and loads being applied.

Thanks for your help.

Boondocker

[dgd]

When the turbine is at one of the 300 watt transitions from bulkMPPT to Absorb and the vibration starts could you try using the Classic configure to turn off the Aux2 and see if the vibration continues or ceases?
This will show if the vibration is actually associated with the aux2 switching in the Clipper's resistors.
It may also be an idea to remove the Clippers door so you can see the activity LED on the Teledyne 3 phase SSR and confirm aux2 is controlling the SSR.

This should be safe enough to do as the Clipper's voltage clamp will still be active and prevent the turbine running away, just make sure you have the clamp voltage set to match your Classic model on the little rotary max voltage pot that's on the Clipper main pcb. There should be 150, 200 and 250 positions marked on the pcb.
In any case be at the Classic and Clipper so that you can stop the turbine if a wind gust makes things exciting.

Dgd

[Boondocker]

Hi dgd,

The LED  SSR in the Clipper does light-up when the Classic switches from BulkMPPT to Absorb.  It appears that the Aux2 PPW output has to be above a certain percentage, before it is shown on the Classic display. 

Turning off Aux2, the vibration ceases when the Classic transitions from BulkMPPT to Absorb.     The vibration does return when rotor rpm climbs to Clipper voltage turnpot setpoint of 125 vdc.   Exciting indeed, there are some good wind today.  The turbine bangs pretty hard when this Clipper voltage limit is reached.

When the turbine is shutdown using the switch on the Clipper, there is one short vibration shutter and spinning halts within two revolutions.  The wind was near 15 mph.

Boondocker

[Halfcrazy]

Boondocker
It sounds like the resistance may be to stiff. What resistance value clipper do you have? And is it the 4KW or the 1.5KW?

Ryan

[Boondocker]

Ryan

The Clipper is 4KW with 1.6 ohm resistors.

Boondocker

[dgd]

Boondocker,

As Ryan says it may be the resistor values that need adjusting.
For 1400 watts what are the voltage and current settings in your wind curve in the Classic?
Maybe just post the wind power curve you are using, shouldn't then be too difficult to calculate a good resistor value

Just one other thought about the cause for the vibration.
If there is a wiring problem, loose connection, shorted or lowish resistance between two phases or one phase to ground
then inserting the Clipper resistors may be unbalancing the turbine or making the unbalance bad enough to chatter the turbine rotor. Although if this went on too long I think you would see mechanical evidence of this at the turbine or worse some stress on the turbine wiring components.

dgd

[Boondocker]

Hello Dgd,

Below is the wind curve table.   1400 watt output,  28dc nominal battery voltage, will occurr at 115 volt input point with the 40 amp setting.

The turbine is set-up to docile at winds above 15 mph.  It begins to furl in 15mph wind and is completely furled at 22 mph.     My desire is produce 100 to 300 watts in  9  to 12 mph wind.     The current blade diameter is 13.5'  and accompishes this power levels. 

I'll take a look at the connection, and resistance between stator phases.    There are not too many hours on the turbine,  only run it seasonally.



     amp   dcv
1   0   40
2   1   54
3   4   66
4   8   73
5   13   76
6   18   79
7   22   82
8   25   87
9   29   96
10   35   105
11   40   110
12   50   115   
13   70   116
14   80   117
15   85   118
16   91   119

[dgd]

Boondocker,

Looks like for the 4Kw Clipper the resistor pack options are the MNCRP unit that comes in resistor values of
0.4, 1.0, 1.6 and 4.0 ohms.
Maybe try a lower resistance and let the turbine fly a little easier when clipping, over to Ryan....

dgd

[Boondocker]

Dgd,

Thanks for your advice.

Yesterday I went searching for possible shorts in the wiring.  Disconnected the lightening arrestor  on the 3 phase wiring and also the arrestor on the DC buss, checked the termination connections (wires are snug and lugs tight).   Today, I'll look the resistance across the phases of the wires where they terminate at the Clipper.  Getting a better quality multimeter, with fresh batteries, to compare the resistance between phases.

When hunting season is over, I can take the stator off and have it meggered for a short.  Just to make sure.

The winds were light yesterday, so it a much better day to do an evaluation with AUX2 off.  The turbine ran smooth in all the variations of wind speed (4 to 9 mph),  while the controller pumped out 50 watts nearly continuously to the batteries in FLOAT.  The turbine speed would just flucuate with the wind and the volatage would rise close to 100dcv.

Allow the turbine "free wheel" upto the higher rpm's and it continue smooth turning; indicates the rotor and blades are balanced and tracking well. I'll spent considerable amount of time balancing the blades while on the alternator and fine turning blade tracking earlier.

When returning the AUX2 setting back to clipper mode, the vibration returned when the  Teledyne SSR active LED is on.  I would not describe the vibration as server, a tower is great amplifier.  However, over the long run will increase wear and tear.
 
Overall, it is pretty amazing watching the Classic and Clipper combination controlling the turbine.

Boondocker

[dgd]

Boondocker,

Take a look into the Clippers resistor box, perhaps removing the unit from the Clipper.
Just confirm the resistors are all connected correctly and the wiring and connectors all look good and tight.
I see from the MN docs I got with my Clipper there are several ways the actual resistors can be configured to arrive at the per-phase resistance. Each may be using two 0.8 ohm resistors in series to give 1.6 ohms, if so then you may be able to simply rewire to use only one resistor and see if this improves the vibration when clipping.

Dgd

[Boondocker]

Hi Dgd,

Took a close look at the resistors in the Clipper.  There are configured 1.6 ohms in series and all of the connections are tight.

Also spent some time playing with the AUX2 setting, voltage and width.  The voltage original setting was 5.0 and the width 1.0.  Increasing the voltage to 20.0 and width to 5.0 seemed work best to soften the vibration some.  The turbine spins noticeable faster before the Clipper is activated with higher voltage settings.

Concerning  the resistance, with the Clipper acting too aggressive , wouldn't lowering the resistance increase the braking action?  The PWM signal to the SSR creates a short across the resistors.       I'm thinking a more "direct short" (lower resistance) makes for harder breaking of the turbine.

Boondocker

[boB]

If all 3 phases are not working the same, this will also cause some unbalance and vibration.

You might check phase to phase AC voltage when either in MPPT just to make sure they
are are fairly close.  Not exactly, just all in the ball park kind of close in voltage.

[dgd]

Concerning  the resistance, with the Clipper acting too aggressive , wouldn't lowering the resistance increase the braking action?  The PWM signal to the SSR creates a short across the resistors.       I'm thinking a more "direct short" (lower resistance) makes for harder breaking of the turbine.

I was thinking that the PWM action of the Classic is to vary the  resistance on each phase from infinite high resistance (ie no shorting) when no/low duty cycle PWM down to the resistance of the Clipper's resistors when at high, 100% duty cycle.
When your Classic starts the PWM process and the Clipper starts shorting the phases  then you notice vibration. I would guess that the Classic is getting to maximum duty cycle pretty quickly and your turbine phases are shorted via the actual 1.6ohms on each phase.
If this resistance is too high then the turbine may not be braking sufficiently, the resistors not absorbing enough power from the turbine so the turbine tries to produce more power than the Classic can take plus the resistors can dissipate.
The excess power then generates noise and vibration, ie the turbine is not happy..
Hence my suggestion that lowering the Clipper's resistance values may allow the resistors to dissipate more power and the turbine run easier.
Normal power generation should not be reduces as the PWM may find a more suitable resistance value above the 0.8 ohms and the 1.6 you currently use.

Just my logic which may of course be incorrect, boB or Ryan may know better 

dgd