Effects on a 480 V 3 ph Dropping 2 Legs for Single Phase

https://www.carroll-meynell.com/three-phase-to-single-phase/#:~:text=THREE%20PHASE%20TO%20SINGLE%20PHASE%20TRANSFORMER%20OPTIONS,current%20in%20the%20third%20line.

You need to flesh this out a little more...What is the size and type of load you'll be supplying..? You need to figure out what the newly configured output will be to see if it meets your load requirements reliably...and take into consideration any future changes that might occur...

thanks, that link helps a lot.

If you drop 2 legs that will lower the load on the generator quite a bit, most generators like at least a 50% load, and 75% even better...not to mention the output would drop by 2/3 and even more with another transformer to raise the voltage...your efficiency would be in the toilet...for a temporary emergency application this might be ok...but long term I see problems...

Its a continuous, gen plate posted.

Thanks,

480V is the highest system voltage for a system with 460V nominal voltage, I think. Please check the name plate.

Rating of 500kVA / 500kW suggests that the load to be connected is completely resistive. If the load power factor happens to be other than unity, the machine will not be able to deliver 500kW.

240V Single phase load is not much I suppose. The idea of connecting between two phases through a step-down transformer is a good idea and will help reduce load unbalance on the machine. You may be selecting a 460V / 250V single phase transformer, I suppose!

At my computer now... Attached is the name plate...

Here is more information on this. Gets drawn out into a story.

Last year, I bought a 3PH wood planer that had a 10HP (7.4 kW). with the intent of getting a 20-25 kW 3PH generator. pretty common on the market.

My brother took over the dairy family farm, and he has a 30 kW PTO (Tractor driven Power Take Off) driven single phase generator when the power goes out due to weather, etc..

The county where the farm is located, the county municipality is selling their excess equipment has a 500 kw genset. Now the my brother that has the farm, 20 kW PTO.

Now the farm is on a single phase grid, so all the electrical motors there are single phase. The problem my brother is. 25 kW generator doesn't cover the the minimum essentials for taking care of the herd and milking cows.

to power

• Well Pump
• Power the robotic milkers,
• Manure Pumps
• Silo unloaders
• Mixers
• Material handling equipment
• etc...

with a number of 10HP, 20HP, 30HP, motors, he needs to really watch out from over loading the generator. He wants me to go in with him and bring my wood working equipment there, which isn't bad.

But that Genset is huge, ie over kill, but the price is great. the other item. its powered by a 760HP Cummings???

For me starting it to run a 10 HP planer is ridicules. But for my brother, if the power would go out, It'll still be over sized, but the farm could still work on schedule without having to parse out what to run.

The genset itself is going more than reasonable which is the only reason its being considered.

Now with the responses, which I appreciate, I don't think it'll be an issue with the exception of a stable power to the robotic milkers.

I'll have to reach out to DeLaval representative where he purchased the robots from see what they have to say.

Thanks for all the comments... I'll let you know what we'll do.

Thank you, also nice tip about added loads selected different phases.

as far as transformers, there was a large regional box store that shut down. (ShopKo). I saw that the entity??? that bought some of the locations had a lot of transformers…

Maybe just check with Cummings then. If you're planning to run a 760 hp (567kW) engine with a 500kVA generator whilst only pulling 50-100kW, the electricals may be fine, but the engine itself may not be so happy. The older gensets apparently didn't really enjoy running at low percentages of output for extended periods. We had some issues on a 500kVA standby genset that usually ran at 75-120 kVA, but I cannot remember the exact details - this was long ago (carbon & soot buildup, and something else?). And yes, the engine is cheap, but you're going to pay for the diesel - a lot. I'm sure Cummings will be willing to chat to you.

Also, depending on how you connect, make sure that the neutral can handle the Amps coming its way.

Yes, what does cost, if the electricity goes out for 1-2 days and it did happen in the past, the loss of milk from the cost, and the insuring losses from the cows going, off feed, pays for it. Not to mention the herd health as well as any veterinarian bills because the cows weren’t milked on time.

that is the criteria, sure the cost is initially cheap, but even if it wasn’t, if we use it once, the savings more then paid for itself. If it wasn’t for that, we’d take a pass on it.

Quite correct - both the engine issues and the fuel & maintenance costs relates directly to usage: If it is used once a year for a day or two, then those issues are pretty much non-issues, whereas if you're using it daily or weekly it adds up quickly. In your brother's case it does not seem to be a major consideration. (I think I've been conditioned by our extensive daily outages - thankfully none for the past 4 months - and the fuel & maintenance costs of those!)

If the generator is delta wired, then any live to neutral will be 230-250v. The 460v is phase to phase.

No transformers needed.

Just split the load between phases so it is as close to balanced you can.

As someone previously stated, the load on the neutral can be higher if out of balance, so the main neutral wiring needs to be heavy enough to cope.

Line to neutral voltage is 277 volts, regardless of connection.

Might be worth remembering that 220 'single phase' actually floats; unconnected to neutral. I'd take a careful look at the load, to be sure that nothing undesired is going to end up 'hot' due to neutral exposure, and to be sure that the neutral in the load hasn't gotten tied to the chassis by someone during a past mod.

Far lower risk to just use a transformer.