Generator Winding Heating with solar panels 2

[dontexplode]

Have a site with four 3.5mw generators that are not accessible for various reasons.
site visits and install are two hours every week.

The intent is to hookup some solar panels and charge controllers to the windings of the generator to keep moisture out.
Utility power is not available.

The solar panels are a 2kW array, an outback FM80 battery charger and want to connect the battery charger FM80 to the windings to heat them up.
There is little to no consequence for losing solar power and this is just to help.

I obviously cannot connect the output + of the FM80 directly to one end of the winding and connect the - to the other winding because the resistance is so low.

Does it make sense to install a resistor before one of the connections to limit the current? 5A's seems reasonable for this application.
FM80, 120V, 5A, 24ohms,

any other thoughts? would like to keep this at dc

does this even make sense?

 

[IRstuff]

So, you want to hook a battery charge to the windings of a 3.5 MW generator? What's going to happen to the charger when the generator starts generating power?

Why are the windings so exposed in the first place?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[MacGyverS2000]

What's going to happen to the charger when the generator starts generating power?

Ooh, ooh, ooh, I know this one... pick me, pick me! I'm not sure the OP's handle is going to fit reality, though ;-)

Seems to me an easier thing might be using that power to run a dehumidifier and/or heater coils in the same area... keeps the electrical side of things MUCH more simple.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[dontexplode]

the generators are not allowed to run for the next few months.

the space to put a humidifier is really tight, we don't have access to utility power.

Thanks so much for your insight.

 

[dontexplode]

So the current design is 1.8-2kW of solar panels, pv combiner box, FM80 charge controller, or Outback Radian if wanted it could be connected to grid at later date, Batteries, DC disconnect or small dc load center. Obviously this won't be permitted and ul listed.

First thought is to put in a resistor rated for 48Vdc, and rated for 1000w, and 10ohms. v=ir, so 48=(4.8 amps) 10 ohms which equates to 230w. and we could connect three of these in parallel to get 690w for each of the phases. Custom connections and etc would be required. that way some current will flow through the windings and keep some moisture out

https://www.digikey.com/product-detail/en/ohmite/TA1K0PH15R0KE/TA1K0PH15R0KE-ND/824263

 

[Compositepro]

If you place a current limiting resistor in series with a low resistance, almost all of your power will be dissipated by the resistor with no heating in your coils. Ohm's law.

 

[dontexplode]

that's what I was afraid of.. just dissipating all the heat via the resistor.




The other option is to install 48vdc rated heater tape and connect that to the dc load center and wrap those around the items you want to heat up

https://www.grainger.com/category/e...hvac-and-refrigeration/ecatalog/N-ra0Z1yza2dz

The link above are 3w/ft, 48vdc, and at 16ft it'll be 48w. The installation could include a dozen or so of these.

 

[Compositepro]

If you want resistive heating of the coil to occur, you need to measure its resistance and then calculate the current required to get the Watts of heat desired. The voltage is then IR. A welding transformer is what you need to use. Or better, just use a space heater and avoid the other dangers that have been mentioned.

 

[dontexplode]

Thanks

the resistance of the winding is not currently know, but it is a 12kV, 3.8MW unit. The resistance would probably be pretty low and would just drain the battery very quickly.

what's an easy way to control the dc current without losing all the heat?

 

[VEBill]

"space....really tight"

If the generator compartment is made of metal, then perhaps the heaters could be attached to the outside of the compartment, to heat by conduction. Possibly held in place by means of magnets (assuming steel), sort of like a block heater used on car engines in very cold climates.

Of course, if there's sunshine, then you could get more heat into the compartment by wrapping it in black plastic film. The old 'kilowatt per square meter' solar radiation and all that.

And, cold humid foggy days might lack sunshine.

 

[dontexplode]

Thanks for your thoughts VE1BLL!

 

[IRstuff]

What is the surface area of the casing? Who came up with the 1 kW power value? You need enough heat to stay above the dewpoint. At 0.5W/in^2, the 1 kW would cover 2000 sq. in.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[itsmoked]

Just stick magnetic-base heaters or heater tape to the actual generator bodies and call it a day. Trying to heat via the winding is a major pain in the butt fraught with lots of little issues poorly dealt with out-in-the-boonies.

The only complex thing you might want to add would be to hook up the heating thru an auxiliary contact to disconnect it whenever the generators are active.

Leaving the systems isolated is win-win. The idea is that the warmest thing is the last thing to feel moisture effects so having the generator cases warm trumps everything else in the room/enclosures. That should accomplish what you're after.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[dontexplode]

Thanks itsmoked

great insight

 

[FreddyNurk]

The alternators don't have their own anti-condensation heaters already fitted? I know most of the units I have dealt with at LV are routinely fitted with such equipment.

I have also seen silicon tape heaters fitted as close to the windings as possible in order to provide similar function after suspicions were raised regarding the reliability of OEM units. I believe that there are also new ceramic PTC elements or similar now available that self regulate their temperature, which would also be better for this application, we used some small ones recently for an anti-condensation application, and they worked well.

Either way, a separate heating system capable of being easily shutdown when the units are in service is best, rather than trying to integrate with the windings of the alternator.
Other thoughts:
1. Can the FM80 run without a battery? I seem to recall that a lot of the solar stuff is designed to have a battery as a dump load, and doesn't like running without one.
2. What happens at night if you don't have a battery? Surely that would be the worst time for condensation issues?

EDMS Australia

 

[waross]

Put the resistors inside the generator housing. That puts more of the heat where you need it.
Cheap strip heaters are effective, and... Cheap.
If you mount the strips inside on stand-off spacers the convection heating of the generator will be more effective.
Actually it is the core that needs to be heated although the core may be heated by heating the windings.
If the dew point rises above the temperature of the core, instant condensation, lots of it until the condensation rises the temperature of the core.
You need batteries to carry you through the night and early morning.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[VEBill]

Seal up the whole thing in plastic film (to keep out the weather, specifically moisture), and with several as large as possible bags of desiccant squirreled away inside. Tag the bags with 'Remove Before Flight' tags so they're not forgotten about during commissioning and start-up.

Ref:

https://www.sorbentsystems.com/largebags.html

 

[waross]

You should have permanent heaters in a generator of that size. Contact the manufacturer for a anti-condensation heater kit for the machines. Install the heaters permanently.
Now the issue to be solved is providing suitable power to the heaters.
Typically anti-condensation heaters are rated for 200% of the supply voltage and develop 25% of rated watts.
This ensures almost unlimited life of the heaters.
I have had more than one failure on very old machines where a wire or a connection had failed due to corrosion. In every case the heater was serviceable and was put back into service after repairs to the wiring.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[OperaHouse]

There are power point converter boxes that will go right into a resistive heating element if it has one from the panels. Another way off the shelf, you could add a battery to the FM80 (I assume you will be running at night) and get an AC inverter. Find one or multiple transformers to drop the voltage lower at higher current suitable to the windings resistance. Add an automatic cutoff for low battery. Inverters will shut down with internal controls, but won't restart automatically.