Discussion in 'Connecting to the Grid' started by Southpaw, Aug 26, 2011.
Sorry Ken no answers on that, looks like Tom does though.
Larry, if you have a better relay idea let me know. Otherwise we could use a Fat FET 100A 100V ($22).
Na, on the electronics part. I am not to familar but, i am interested in why the dump load relays are failing.
Is it because they are not right from the factory, or just the wrong loads on them? I would think that if a person was using a 10-30v GTI 300w and using a 12v dump load coil at 300 watts that is 25 amps. Is that relay rated for such amps? 600w at 12v would be 50amps. 10-30v 300w inverter being used with 24v dump coils is 12.5 amps. that sounds more reasonable to me for that relay.
500w GTI 10-30v using 24v 300w dump coil same thing, 600w 24v dump coil at again 25amps.
22-60v 500w GTI using 48v 300 watt dump coils. 6.25a, use a 600w bank of dump coils at 48v you get 12.5amps.
22-60 1000w inverter using a 900w dump coil at 48v is 18.75 amps.
use a 1200w dump load at 48v 25amps
So we need to know what all the relays are rated on the dump controller regarding amps to combat this problem up front. If it is a volatge problem or just a POS relay, we at least have to make this part right to make sure it's not us frying them. I know there are no directions with these inverter's so it's anyone's guess and sometimes also to late.
I will look in my 250 (10-30v)GTI tonight to see what the dump relay is rated on that one.
250w and 500w Sun GTIWDL 10-30v DC input
I believe this is the dump control relay in the 250 which is the same one in the 500 both 10-30v
Regarding amps through the dump relay250w GTI16a rated relay for dump coil control it also has an ATC fuse rated at 30amps.The ATC fuse (looks like car fuse) seems to be fusing the main positive DC input.(I think??)
I would think if you:
Use a 12v 300w dump coil that can fry the relay. (25 amps)
Use a 24v 300w dump coil and the relay you would think would be fine (12.5 amps)
500w Sun G 10-30v
Same relay 16a and it has an ATC fuse of 40 amps
Even using a 350w dump coil could work too at 24v (14.5a)
So to me, it looks like 12v coils are out for these GTI dump loads, and no more then 350w coils to be used on these two units.
Q#Any thoughhts on the above?
ATC fuse ratings in the GTI's
10-30v inverter at 250w would be 250w/30v is 8.3amps
If it was stuck in 12v that would be 20.8 amps
10v would be 25 amps (who runs a 10v turbine?)
Any higher voltage and the amps are lower then 20.
So again why such a high fuse. What can take 30 and 40 amps in these inverters?
Q#2 Why are the ATC fuses so big in amp ratings?
A dump load rating is usually the rating of the turbine and then some. Sometimes plus 5 to-20% more.
Q#3 Are we now to think with these types of inverters that they do not want the inverter/ turbine rating to be exceeded?
I know using 24v and48v dump coils are not going stop the turbine which is what we would not want but to merley slow it down.
Please note i am referring to only the dump coils WN sells. (300w 12, 24, and 48v) If there are others at different voltages and or watts then the calculations do change but the relay remains the same amp rating of 16a in these two units. I would also consider staying about 20% under that relay amp rating to make it last longer.
This is my approach to look at first before i would think about modifying the units. If these calculations have been tried and do not work then i guess the relay system needs an external dump control which would be bad news for these inverters since this is half the selling point of them. I can tell you that the larger turbines (UL inverters) i have installed have an extrenall dump load controller like SMA Windy Boy, and Aurora. I also believe Ginlong needs one too. Ya know all of this trial and error could be avioded if we just knew a China speaking wind dude.
....................................................and we thought we could just plug them in. Ha ha.
If we need an external relay system then you have presented the best idea with that relay you proposed as far as i can see.
Guys that is why I am using a separate controller to dump to dump resistors. My controller had a 16 amp relay and the first big storm melted it closed. It was not battery tied and had two 12v 300 w dump resistors on it.
So after I replaced it I hooked it to the Heavy Duty relay to connect to the dump load. And I have 900 watts of 24 volt resistors on the dump. With two garden tractor batteries for a battery tie.
All has been working fine since.
On the other point of using 350 watts of 24 volt resistors on the dump terminals may or may not work if you have more than one turbine. More than one and it probably will not be able to slow the turbines down.
I have everything setup to do a new video of mine working if we ever get some more wind over 30 mph again this winter or when ever. The relay never is engaged more than a few seconds and by then both GTIs are in full swing to hold the turbines down on mine. And this only happens when the gusts are over a 15 mph increase at least.
Thanks Tom ,
I hope you do get those winds. i have not seen any over 25. I have some new toys in the works to record all the data while i am not home. Wind speeds and AC watts with times and dates.
Above,I am speaking of one turbine and one GTI per set up. I think if you had 2 or three turbines and two or three inverters all of the inverters would need their own dump loads if all the inverters were the same volts and watts. I,as yuo know, have mine ending with 22-60v. I am pretty and i say pretty confident that 900w of coils at 48v will not fry my relay on the 1kw inverter with (1) 1kw 24v turbine. In my case i am expecting to see that rarely and for a very short time, not continuous duty. I know we are looking for the overall answer but i still would like to know what everyone has been hooking up to the dump coils before they failed.
Can you tell us what you had hooked up when they failed?
Leamy, I have 3 - 800 watt - 24 volt turbines. To each turbine I have a 10-30 volt 500 watt Sun GTI and a 22-60 volt 500 watt Sun GTI hooked in parallel. Nothing is hooked to the dump terminals on the 10-30 volt GTI's. The plus and minus dump terminals on the three 22-60 GTI's go to plus and minus buss bars. The plus and minus buss bars are then connected to the dump load. The dump load is two 1000 watt, 24 volt units hooked in parallel. Each unit consists of 6 coils. I lost 2 of my dump load relays on the 22-60 volt GTI's in the last big blow. The GTI's produce watts OK till you hook up the dump terminals. Than it's like you put on the brake. There is now voltage all the time at the dump load terminals. The 10-30 volt GTI's came thru everything OK. At the time of the winds the 10-30 volt GTI's were unplugged. Only the 22-60 volt GTI's were running. Had 55 to 60+ MPH winds for two nights. Saw over 80 volts a couple of times. Now running the GTI's with no over volt protection. Afraid if it gets over 60 volts, the turbines will free wheel. When bigger winds come I have to switch over to my charge controller and battery bank.
OK.......Slept on this one last night.
If we use max current running thru the relay at 13 amps.
Have to remember if you hook the resistors in parallel the resistance goes in half and then as you add more the resistance drops even more.
So for grid ties we are going about this wrong.
Take a 3 ohm resistor.
12v divided by 3 ohms is 4 amps.
30v divided by 3 ohms is 10 amps.
60 volts divided by 3 ohms is 20 amps.
So the only way to keep from blowing grid ties is do the math.
30v divided by 13 amps is 2.31 ohms max that will dump 390 watts.
60v divided by 13 amps is 4.62 ohms max that will dump 780 watts.
You have to series and parallel the resistors to get the desired wattage.
If you are using two 24 volt resistors at 3 ohms on parallel the ohms goes to 1.5 and at 60 volts the current would be 40 amps and watts would be 2400.
That is why we are burning relays up.
Also without a battery tie. If you do not have enough resistor to drag the turbine down and the voltage rises you will still burn up the relay.
OK .......Go ahead and correct me if I am wrong.....................
Also for BlueJay on the tail issue. I have noticed mine furling when it gets hit with a big wind gust. And when it dies down the tail drops fast and turns it out of the wind. I will be tying mine down straight as I do not have sustained winds all the time and never over 25 mph. But for your issue you might want to try a rear hatch shock on your tail. It will allow it to furl but will slow it on the way back down. Should help out with power production as well as cutting down the violent action on it.
Just a thought.
View attachment 694
TomT is on the right track. I agree that the wrong combinations of resistors can lead to excessive current and frozen relays.
Here are some calcs to help going forward. Select the "watts" column below that is 20% more than your turbine will ever produce. This is for margin. So if your turbine can produce 800w, choose the 1000w column. Below that is the equivalent ohms and amps for a range of dump voltages. Remember, even if you have the dump set for a given voltage, the voltage can still rise because it is a function of the turbine RPM.
I then show the 30V and 60V GTI dump cases, and the combination of WN dump resistors that will work. There are 3 resistor types, which I refer to as Type A, B, and C. They are nothing more than resistors with a different ohm levels. I'd rather not refer to them as 12/24/48V resistors as resistors could care less about the voltage applied to them. Their values are at the bottom of the table.
This table took a good bit of number crunching and puzzle solving but it should be good. The idea was to get the ohms close based on the top chart while providing enough power dissipation capacity based on the power being dumped. As you can see in the yellow, that capacity can be exceeded, but since the "300w" resistor rating is meant as a sustained rating it should be OK since dump is suppose to be intermittent. You can always do the math and add watt capacity if you are concerned about it in your case.
The amp table tells the story on the GTI relay in question. If indeed the relay is rated at 16A then on a 30V GTI it is likely to fail if the load is set to 500W or greater. A 60V GTI can pass up to 1000w then its relay is likely to fail/freeze.
In general, it's a good practice to derate by at least 25%, so I would tend to not run a 16A relay above 12A. That means 300w at 30V and/or 700w at 60V.
Hi Ken, I had a 500, 10.8-30 Sun G go the same way. For a long time I did just keep running it with the dump disconnected and let it go to over volt,,, it kept on working.. I later was in contact with a real nice person who sells them on Ebay,, Ronnie Freeman " Using Gods Free Energy" He repaired five (5) Sun G 500's I had that I thought had fried... Seems Sun G instructed him that the mosfets they used where too weak so just upgraded to a better ones. If you are interested in speaking with him I can give you his email address.
Hi Murray. That would be great if I could get his E-mail. Was the cost to fix reasonable? Thanks Murray.
Hi Ken, firstname.lastname@example.org
Cost for me was very reasonable, but you will have to work out a price with him.
He is a real nice person and very helpful.
Been looking around and finding that relay contacts should be derated as voltage increases. So if the relay is 30a at 12v that at 30 volts it should be more like 12 amps max ?
Also might add the rating from the maker of my controller board says it will handle 30 amps. But from looking at the spec sheet it is rated at 20 amps at 12 volts. But they are using a beginning voltage at 10 volts. What is up with that?
Wow great info. So now that we have the calculations maybe they will survive better?
I'm not an expert on relays, but the contact material and thickness makes a huge difference. Unless a person knows what the relay is made of, I'm not sure one can confidently derate its current vs. voltage. It seems there are mainly automotive types (12Vdc) and 115/208Vac types out there; very little in between.
Here is an industrial 40A DC Solid State Relay that uses MOSFETs. It can be used with the circuit I posted earlier, tweaking the zener as needed to set the trip voltage point. It's a bit pricey (~$70) but it would make all your relay concerns go away. At 40A and 60V you are covered up to a 2400w dump. Nice.
That I would agree with. With the mechanical relays if you have too much current it will weld the contacts together because there is not enough surface area. So the solid state ones would be alot better.
Here's a $36 one providing 20A up to 100Vdc. Good for 600w for the 30V case or 1200w for the 60V case:
Another 40A one; same product line. $56
Another SSR line:
Since we are on relays, do they make an SSR NC? I could use on for my switching system. i know they make another part to make it NC to go with it but i just wanted the SSR NC i it exist. I looked around but could not find them.
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