ST Head Waveform Regulation

[WStayton]

  So, I guess what you guys are telling me is that, in asmuchas  will be using a four cylinder engine runing at 1800 or, maybe, 2560, rpm, and will be ordering my ST-24 with an AVR controller, I shouldn't have a problem!

  I will also, per Bob. make sure that I have a fuse of appropriate rating, in the output of the AVR, so that it won't have a fit trying to maintain voltage on shutdown.  I'm assuming that this will still be neccessary, even if I don't shut the ST down under load so as to avoid needing "field flash" upon restart?  And, does this mean that I will require 1 fuse per shutdown, because the AVR will try to maintain voltage as it is going away?  Or should I rig a switch in the AVR feed and shut that down after shutting down the load on the ST-head, but before stopping the engine, and thus avoid the "1 fuse per shut down issue"?

  It's nice to hear, for a change, that what I'm planning is not completely stupid!  <grin>

  Thanks for all the input, guys!

Regardz,

Wayne Stayton

[sailawayrb]

I don't think you would ever want to have a shutdown with loads still on your ST because of adverse brownout effect.  You might want to build something to ensure that this will never happen.  See "Engine Speed and Voltage Protection System" in below link for what I did:

http://listerenginegallery.com/main.php?g2_itemId=351

I defer to other's expertise regarding AVR issues as I don't use one and I am not really a fan of using one for this application...too much complexity for too little value IMHO.

Bob B.

[Tom Reed]

If you're feeding into the xantrex inverter discussed, it will disconnect from the generator at around 108 volts and/or frequency out of spec. So there should be no need to disconnect before shutdown. It also has a delayed connection to the generator to allow the engine to warm up.

[rcavictim]

Simply locate a 3-pole breaker at the STC head and open it when you shut down the diesel engine.  That way you can start the engine without a load and let it warm/stabilize for a bit before applying load as well.

My selection and purchase of the 24kW/30 kVA STC head was a deliberate ~2X oversize based on the thinking that I would not hurt it by operating under load at much slower shaft RPM than 1800. This was essential in my wind turbine app. I have one in operation on a Changfa 1115 engine and have operated it loaded at as low as 1200 RPM without anything getting warm or failing. So far so good.  I also have shut mine down with as much as 9 kW resistive load from rated 1800 RPM and never needed to flash the field yet.

I think starting up one of these heads or any head is a bad idea under anything approaching a real load and may in itself be the cause of needing a re-flash of the field rather than any loss of magnetism during a loaded shutdown.

[WStayton]

  I don't think i will have a problem on normal shutdown or start-up, since I plan on having a disconnect for the output from the generator-head, along with it own 200 amp circuit breaker across the output, but I won't be using the circuit breaker as a shutdown (except in an emergency!) becuase my uncle, the electrician, told me that shutting off circuit breakers under load causes excessive wear such that they start tripping under lower current.  Not sure if that is true, or not, but it is cheap insurance to operate as though it was/is.

  Where I would wnticipate having a problem is if the engine shut down without supervision such as from a plugged fuel filter or, God forbid, loss of oil pressure!  If that were the case, there would be nothing to shed the load upon shut down, so, I am hoping that this is where the fuse in the AVR feed would come in!

  Also, I'm not sure if the automatic shut down of the inverter occurs before the AVR draws excessive current, since I think that it will continue to increase the voltage until it reached the limit of it's supply voltage.  Anyhow, the fuse on line to the AVR makes that a moot point - I would rather buy a $0.25 fuse than a $100.00 AVR any day of the week!

  Also, I will have 120/240 loads other than the inverter - things that I don't, or can't, run off of the inverter because of lack of capacity will run off of the generator - really, I envision shifting the whole AC distribution panel over to the generatro when that was running, so the only load on the inverter would be its battery charger function - admittedly, a big load, but a singular one, nonetheless.

Thanx for the input!

Regardz,

Wayne Stayton

[rcavictim]

  I don't think i will have a problem on normal shutdown or start-up, since I plan on having a disconnect for the output from the generator-head, along with it own 200 amp circuit breaker across the output, but I won't be using the circuit breaker as a shutdown (except in an emergency!) Regardz,

Wayne Stayton

I do hope you don't intend to place a 200 amp breaker across the output of the gen head as a shorting switch to bring the thing to a screeching halt.     It might be cheaper to jam a crowbar into the engine crankshaft to effect the same result since crowbars are cheaper than 3-phase 200 amp breakers.

[WStayton]

rcavictim:

  Bad choice of words on my part!!!  <grin>

  You're supposed to read what I mean, not what I say!!! <smile>

  Actually what I meant was that the 24 kW ST generator-head will have its own 200 amp, total, 100 amps per leg, in line with the output so that there is no way that I can try to draw more than 24 kW out of it.  I THINK that I need this because the generator-head will feed the charge function of the inverter and the main 200 amp panel for the whole place, this way I could be drawing 50 amp for the charger function of the inverter and still have a rogue(sp?) load of everything trying to start at once and drawing more than the  150 amps still available.

  BTW, I am assuming that the 100 amps that is available form the inverter for battery charging is as 48V DC, yes?  Which means that I need, in round numbers, with charger losses and everything, 50 amps of 120 V AC, yes?

  About the 200 amp breaker across the generator for a dead short:  I may be dumb, but I don't think I am stupid!  <grin>

  Though, I guess, it is better to say something and make SURE that I'm not stupid, so thanx for keeping me honest! <smile>

Regardz,

Wayne Stayton

[Ronmar]

Your plan sounds OK, 100A per leg = 12KW per leg @ 120V...  I have circuit breakers on my generator output.  They are open for startup, and again open for shutdown to remove the load from the generator/engine... 

In the case of a non AVR ST head, a simple shutdown could be rigged from a simple voltage sensing circuit.  Since voltage output is RPM dependent in the plain ST head, a droop in RPM caused by a missfire or runing out of fuel, would cause a voltage droop, and the sense circuit could open a large electrical contactor on the output once a low voltage was detected.  Clean electrical break, no brownout.  the same circuit could then also shutoff the fuel and secure the engine.  It then becomes a simple matter to add thermal sensors to provide the sam function in an overtemp/cooling malfunction...

The AVR makes this a little more difficult, as it maintains the voltage till it absolutely cannot do it anymore, and a lot of current may trade places while it is blindly trying to do it's job during a spooldown.  The one thing that is predictable about an AVR is that it will maintain voltage by increasing field current.  as you increase load, line voltage wants to drop. The AVR senses this and increses field current to maintain line volatge output.  So for a given electrical load on the generator, the AVR will be providing a fairly predictable field current.  This is where that fuse comes in.  if you measure how much field current you are providing at your maximum load and add a fuse to the field circuit just slightly higher than that max normal field current, you will protect the AVR from feeding any perceived load greater than that, such as during a brownout spooldown... 

If you are putting together your own generator, don't be afraid of the reflash process, it is really quite simple...  In fact, I would say add labeled field reflash terminals to your generator doghouse, and write up a procedure to reflash the field using a car/starting battery...  Be a shame to run the engine out of fuel, then be dead in the water because you do not know how to reflash the field... 

[WStayton]

I suppose this should be a new question, but its getting late and I'm getting tired so . . . I'll just stick it here!  <grin>

I've heard/read that the "doghouses" on ST generator-heads are really just a problem looking for a place to happen in that they break and fall off due to fatigue from vibration.

My intention is to relocate everthing in the doghouse in a new/different/bigger electrical box at/in the control position for the generator which will be about 3 feet from the generator.  It is my intention to run everything to and from the generator in conduit and I plan on a separate run of 3/4 inch conduit to carry the wires from the generator to the stuff that was previously mounted on top of the generator. I guess this would also include the AVR box.

Is this acceptable?  I realize that the shorter the wires between the control "stuff" and the generator-head proper, the better, but is three feet within what is acceptable?

My plan is for the control bench to contain everything to operate the engine and the generator-head, with switches/selectors to turn on the engine operating circuit(s) and to operate the starter and shutdown.  There will also be a 200 amp breaker and a disconnect for the output from the generator.  For instrumentation I plan on having a tachometer, an oil pressure gauge, a coolant temperature gauge, a pyrometer with selector to read fuel pre-injector-pump temperature and fuel post-injector-pump temperature, a 12 V DC amp-meter, a 12 V DC voltmeter, two 120 V AC voltmeters to read each leg voltage, and two 120 V ampmeters to read the current on each leg.  I guess I should also have a DC voltage gauge to read the AVR output voltage.  There will also have to be a selector that has two positions 1) engine-generator and 2) inverter, to switch the whole load to one or the other.  I think that the inverter functions are fixed on/in the inverter and there is no provision for manual remote actuation but if there are remote actuators for the inverter they would be mounted on/in the panel also. I guess the inverter itself could be mounted on/near the control panel, also, to keep all the lines as short as possible.  The battery bank will be immediately at the end of the bench.  I envision a space just wide enough to walk down between the control-bench/battery-bank and the engine-generator.  The four water tanks to hold the cooling/heating water will be another aisle width down the space and yet another aisle space away will be the wood burning boiler.  This whole assembly of pieces/parts takes a space about 22 feet long and 12 feet wide, maximum, which will have to fit in a space 20 ft x 30 ft, so there should be enough room for a tier of fire-wood on the furnace end of everything and still have a reasonable aisle way on the other side, where the space connects with the house.

  Anybody see anything I have left out?

  Input is hereby solicited! <grin>

Regardz,

Wayne Stayton

[Ronmar]

Put your batteries in a separate enclosure, preferably built outside...  Charging batteries and open flame/sources of spark(genset brushes) are a bad combination.  Batteries also containe an incredible ammount of instant energy.  Something going wrong in the charging scheme, or wiring, and you have a potential home/structure wrecking installation.  Plan your safety disconnect fuses VERY carefully, as they may save your life or your home!

[Tom Reed]

You know, I have a hard time believing that an AVR doesn't have frequency sensing in it. 

[rcavictim]

You know, I have a hard time believing that an AVR doesn't have frequency sensing in it.  

I need to do some testing and find out because if it does that is gonna screw up how I was hoping the STC head would operate in my wind turbine.

Anyone have or seen a schematic of these AVR's from China?  Since mine are potted that would be enormously helpful.

[cujet]

My 20/2 Listeroid powered ST-15 setup provides (at times) near useless power. Truth be told, it will run the basic electric motors such as window AC units, well pump and the fridge. However, so many things have trouble with the power that I'm not sure what to do, other than to run down the list of "fixes".  Running "off grid" is an exercise in beeping UPS', grumbling electrical components, flickering lights and unsteady power.

Things that won't run, no matter what I do:

1) microwave
2) air conditioner (central)
3) TV
4) Direct TV sat receiver
5) half of my UPS'

My Robin/Subaru/Homelite generator runs everything without problems.

Part of the problem is the unsteady power of the listeroid, along with very poor governing, allowing the frequency to vary. The other part of the problem is the poor waveform. The combo is unsatisfactory electrical power.

[gregger2k]

I put a SX460 clone AVR on my ST10. Works great, stable voltage, under speed roll off, and no Z winding. I have not had a chance to scope it but no problems yet. The SX460 is designed for brush-lesses generators though. I do not know if it will be harder on the brushes being a SCR regulator. With the higher impeadance of the ST field the inrush current will be reduced somewhat. I believe you must power it from both legs (220v) to get enough voltage for the field, I am.

The only anomaly that I have noticed is that the stability control has little or no effect. Even at maximum gain the generator output is stable. Probably has something to do with the high impedance of the ST head. The clone 4609s are available on Epay for around $70 bucks. Worth a try, worked for me!

Greg

[rl71459]

I have a 1ph 12KW ST direct driven by a ISUZU C-201 (4 Cylinder). It runs everything I have....  I have never had any problems with any electrical equipment ever. Mine has no AVR. I have never had a scope on it to see the sine wave (or lack there of!)

I do have a similar list of equipment (and more)
1) microwave
2) air conditioner (central)
3) TV
4) cable box
5) half of my UPS'
6) cable modem
7) WiFi router
Vonage phone router

Just reference info for everyones consideration.

Rob