480V Split Phase / 400V Threephase (AUS)

T

Thread Starter

Teps

HI there,

First post here. I hope I can get out into the forum and provide some answers to you in the future.

I am an Electrician here In Australia and spent my career so far in Industrial.

Currently I have a job which is putting me to the test so I thought someone might be able to offer some advice to me.

The situation:
A customer who is a Hydroponic farmer currently has "2 Phase" "Split phase" (480V) Whichever you like to call it. Three phase isn't available as it's in a rural area and the power is coming in via a SWER line. (Single wire Earth return)

He has approx 12Kw of pumps on one of the phases + House. The other phase has the processing machinery (only runs 3 Days a week) and refrigeration.

He approached me to install a three phase generator with auto start on the farm.

I can see installing a 2 phase Genny will come up, But they are expensive compared to a three phase here as 2 phase isn't common at all these days.

So My question for the Control forum so I can proceed with how to design this is.

1 - Is having unbalanced Phases on a generator detrimental to the life of it (30-40kVA)

2- If each phase has to be balanced, How close can they be. ~10-15%

3- What is an acceptable startup current ( imagine 10 Pumps firing up at once)

4- If I need to balance the load out, As processing happens only three times per week, + 1 phase won't even be connected. What can I use- IE just go run a few big resistors to "waste" the power?

Please feel free to ask for more information!!

Thanks
 
>A customer who is a Hydroponic farmer currently has "2
>Phase" "Split phase" (480V) Whichever you like to call it.
>Three phase isn't available as it's in a rural area and the
>power is coming in via a SWER line. (Single wire Earth
>return)

SWER so you really only have single phase 480 with a center tap

Why couldn't you spread all the 240 Volt single phase loads over 3 phases of the generator or perhaps consider changing some of the single phase motors to 3 phase?

Are some of the motors 480 single phase, that might make it more difficult since you would now only have 400 between phases.

Interesting problem.
 
The way the place is wired is somewhat limiting to me. I would be a bit of an art to try have certain things change over to the unloaded phase when the Gen set is on etc.

They are all single phase pumps, I don't need the 480V Potential at all.
 
>The way the place is wired is somewhat limiting to me. I
>would be a bit of an art to try have certain things change
>over to the unloaded phase when the Gen set is on etc.
>
>They are all single phase pumps, I don't need the 480V
>Potential at all.

Out of curiosity I googled "large single phase generator", I was surprised to see they are available to 35 kVA, something like that should work but I'm guessing he has already bought a 3 phase 400V unit.

If the generator is star connected I see no reason why it shouldn't run with one phase open provided it's large enough. If delta connected you may need a transformer.

You would have to be extremely careful with the changeover switchgear not to backfeed into the HV line (potential fatal results), I'm guessing that's 11kV, you would need to get the power authority involved from a safety standpoint, need their blessing on the design, it might get expensive very quickly.

If the farmer wants to do it himself, walk away.
Has he considered gasoline powered backup pumps?

I hope someone with more experience in this sort of installation chimes in.
 
Does the generator have 12 output leads? If so, it should be able to be zig zag configured to supply split phase 480V at 67% the 3 phase power rating.

I'm not a generator guru so how reconfiguring and balancing affects life will have to be answered by someone else.
 
Yeah seen the single phase genny. Might just be able to use that and put a big contractor on the bottom on the chassis on the board to make all the buses all at the same potential when running on the genny. then back to 2 when on the split phase, Tho it sends shivers down my spine doing things like that.

Yes definitely going to be making sure it's safe. Using a purpose built 4 pole change over switch.

I need to find out about this zig zag set up it sound like the best option at the minute! Cn anyone spare a thought on it?

Cheers
 
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