Maximum inefficiency

[fuelfarmer]

The power we have available is 240 volt single phase. The transformer is at my house. The end tower drive motor would be around 2000 feet from the 240 volt transformer. That would take some BIG wire even to run small motors. We are going to hook into my breaker panel and run wire to the edge on my yard where the 10 hp single phase motor will turn a 3 phase high voltage generator. The single phase motor will be less than 250 feet from the grid transformer. The rest of the run to the pivot control panel will be high voltage 3 phase. And from the control panel to the drive motors will high voltage.

Going from single phase 240 V to three phase 240 V can be done more than one way. Going from 240 V single phase to 460/480 V 3 phase opens another can of worms because now you need a step-up transformer after you have converted to three phase. It was cheaper for us to just run a generator with single phase power.

[dieselgman]

I thought you had a single phase motor turning a 3-phase genhead... that eliminates the voltage change issue altogether.

dieselgman

[LowGear]

I'm still confused.  I'm pretty sure that single phase systems have 120 volts per leg.  What is the voltage on each leg of three phase?

Casey

[BioHazard]

I'm still confused.  I'm pretty sure that single phase systems have 120 volts per leg.  What is the voltage on each leg of three phase?

Casey

Depends on what flavor of 3 phase you have. I think 480v systems are 277 volts leg to neutral.

At my shop the 3 phase is 120v per leg, or 208v combined.

[dieselgman]

There is more than one 3-phase wiring config. and considerably different voltages can be obtained - Delta vs. Star. 2-transformer vs 3-transformer drop from transmission lines.

I think we can do a more thorough answer, but give me a bit to get it all presented clearly.

dieselgman

[fabricator]

FF, how many gpm does it take to feed that run? Is it gonna be hanging sprinklers or big impact heads?

[fuelfarmer]

I think 5 or 600 gpm. My nephew knows all the numbers.  The end gun is a good sized. The rest are sprinklers. The closer to the pivot point the lower the flow through the sprinklers.

[fabricator]

What about a good old fashioned rotary phase converter? I have several nurseries around here that run large pumps on rotary phase converters, are you gonna run a PTO pump for water supply?

[fuelfarmer]

We need high voltage in addition to the extra leg. Cheapest way to get the extra leg and voltage is to run a small generator. The pump is a direct drive diesel / biodiesel powered unit.

[buickanddeere]

Use a VFD to convert single phase to three phase. Also able to vary the speed too.0

[fabricator]

A VFD that size would be pretty pricey.