omron k8ab

[Shaun Burgess]

hi people am new to this forum am running a 5kw turbine on grid tie was using a eurora interface that fryed a few months back stuck in dump mode . so thinking of using a 0mron k8a vs3 , this is a idea i have can any 1 help . this sensing relay will work nc or no can i set this to nc and at 350 vdc the contacts will open . the contacts will be taking grid powered and power a nc relay and the contacts on this relay will be wired to the dump on the dc side of rectifer hope this makes sence thanks

[Cor van Houtum]

Hello Shaun,

Welcome to the forum.

The Omron relais can be used to set the maximum DC voltage and take action.
The action should be (go to initial state same as when no grid power supplied to relais)
The omron relais can NOT be used to connect to the dumpload.
You should use 2 big relais to swich the Dumpload on the AC generator site.

So when the omron relais have no grid power then the BIG DUMP RELAIS should
fall off and close.
The dumpload should be ON in this status.

Now how it works,

When the Omron relais is ON the grid it becomes active
it will open up the contact (when there is no overvoltage on the sense input)
This contact activates the big Dump relais
The 2 dumprelais open up and the turbine should be with NO DUMPLOAD
And starts spinning.

The Omron sensing input is connected to the DC site of the rectifier.
when the trigger level (pot meter) is reached the relais falls off.
and the 2 BIG DUMP relais fall off and the dump wil be ON.

The timer will be in charge of the dumpload time.
after this time (and when the voltage drops under trigger level) is goes back to normal state and will the dumpload let free

My advice,
Do not put the dumpload on the DC site this will burn the power relais for the dump
because of sparks when comming in and out.

put the dumpload on the three phase output AC in parallel with the rectifier input.

During testing DO NOT CONNECT THE AURORA INVERTER.

First make sure that the turbine will listen to the relais setting and be in full controll.
so the voltage NEVER exeeds 550 volts

Set the voltage on the omron relais just a little bit above the voltage that you feel the turbine should be making in the real world.
The RPM of the turbine should be within these setting.
So do not start to calculate but just observe the turbine and let it brake/dump on a save rpm level.
then measure the voltage output.
Set your Aurora powercurve on maximum 6200 watts about 20 volts UNDER the dumpload omron voltage.
be carefull with chinese generators , they can easy produce 8 Kw when rated 5 Kw
in this case you need two Inverters and a transformer.
And a big dumpload 3x 3kw 8-10 Ohms


Have fun

Cor


good luck

[Rob Beckers]

We've been using these relays for a long time for this purpose. Here's a wiring diagram showing you two options; with or without dump load.

http://www.solacity.com/Docs/Wind%20Turbine%20Overvoltage%20Protection.pdf

I've recently been told that I may have drawn the wrong output pin, that instead of pin 12 the contactor should go on pin 14 of the Omron. I've not had time to test if this is true or not, so just FYI. Note that these two wiring diagrams are "fail safe". If the grid power fails the inverter gets disconnected (and the dumpload switched on if you use one).

Instead of the single resistor for the dumpload, with a bridge rectifier, you can also use a three-resistor dump load without rectifier. As Cor noted, always switch AC, not DC. Contactors for DC are few and far between, and regular contactors will quickly burn their contacts if used for DC.

-RoB-

[Shaun Burgess]

thanks guys . have a few questions in robs drawing he discounts the inverter why. is there any reason for this can i not just dump connected to inverter. also the main reason for doing this is a travel a lot and never at home much. and this is going to be a back up system am using a controller that at 350vdc dumps and has no grid fail save is there any reason why i can not run the to controllers side by side will give me more peace of mind. what size rectifer would i need to use and relay on ac side the turbine is a fortis montana thanks

[Rob Beckers]

Shaun, I'm not following your question. What do you want to do? Run the dump load together with the inverter? Sure you can, though it would take another Omron relay: One to switch on the dump load at a set voltage, another one to disconnect the inverter at another (higher) voltage. Maybe a single K8AB-VW can do it, it's been a while since I looked at those, they have two relays in a single package.

Keep in mind that the dump load would have to be sized such that it keeps the turbine under control even when there is no grid power (and no load from the inverter on the turbine). Also keep in mind that the primary purpose of this circuit is to protect the inverter, not to switch on a dump load. Most turbines come with a controller that already does that.

The Fortis Web site does not provide much detail about their turbines. The Montana is a 5 to 6kW output power turbine with a 3-phase PM alternator. They don't list the voltage at which it reaches full power. If that's reasonable (200+ Volt AC), then the currents will be such that the contactors listed in my drawing should work fine. If the voltage is much lower, then the currents will be much higher and different contactors should be used.

-RoB-

[Shaun Burgess]

sorry rob . what i want to no is it ok to use the fortis controller which is set at 380vdc to dump and if the grid fails with this controller the inverter turns of. and the turbine speeds up to 380vdc before it dumps into 6kw dump load . and say use the omron relay set at around 350vdc sensing side to operate. big relay on ac side threw a recterifer to the same dump dc 6kw dump , so i would have double protection would there be a issue with back feeding on the dc side threw the to controllers. or any thing am missing i could use two different dumps that what am trying to do . and of course the omron will have to be set up to dump if grid fails goes to dump . thanks

[Ben Colla]

I'd also want a way to shut the turbine down when the dump load is active. The idea being that the dump load is an emergency only thing, to use for a short time while the turbine is being shutdown. The time you'll most need the dump load is when the grid fails during a storm, which is also probably also when the turbine will be making the most power. If you blow the dump load, you'll then blow the turbine.

My thought on how to achieve this is with a mains powered electronic actuautor that holds up a weight. When the grid fails, the actuator lets the weight drop which pulls on the manual brake (You might want a shock absorber in there too, so that the weight settles slowly rather than plunge down). Simple and a fail safe system. You probably also want a 5 minute timer or so on the actuator so it doesn't turn on immediately after grid reconnect just in case it drops again 5 seconds later.

[Rob Beckers]

Shaun, I would have to see how the Fortis controller and dump load are wired up, but assume that it is possible to set it up so it switches to dump load at an earlier voltage and/or when the grid goes away. I'm not sure what this will gain you though; if the controller is made properly it should be reliable enough to take care of switching on the dump load as needed.

-RoB-

[Shaun Burgess]

thanks rob . . i would like to use 2 controllers with the turbine for peace of mind thats the reason am away from home a lot. . i think i will use 2 dump loads . i ordered the nc 40amp relay today am going to use this on the ac side . is it ok to wire the wild ac power from turbine straight to the sensing side of the omron relay k8ab vs3 . thanks agin

[Rob Beckers]

Yes, that's how we have used them. The Omron has a 600V AC input, and will handle more than that. The 600V AC translates to over 800V DC, so it'll rarely (if ever) get that high.

-RoB-