High Leg Delta

[Joethemechanic]

You don't replace the service transformer with the DIT, you just mount it next to the VFD, sized only for that drive, just like you would with a Line Reactor. No need to run 4 wires either, you just ground the X0 and leave it that way.

Yes I'm agreeing with you, it's the best solution. Almost zero lead time, and you need a line reactor anyway, so two birds with one stone.

The DIT is never going to waste enough power to mean squat compared to the costs of a serious upgrade like that.

@steve66
Is this a municipal, or a private sewage plant?

 

[jim dungar]

If you are buying a transformer, you could get one with with a 480Y/277 output and then use a 480V drive and motor. You would have to run the dollars though to see if it is cost effective.

 

[tortuga]

The DIT is never going to waste enough power to mean squat compared to the costs of a serious upgrade like that.

yeah it may not be much, but it aint zero, I looked up a Aluminum-wound 75 kVA with a no-load 375 W, full-load total 2829 W.
If Pump 'on' hours per year is 30% = 2628h
I came up with:
On vampire load: ~4,140 kWh/year
Off (idle) vampire load: 0.375 kW * 6132 h = ~2,300 kWh/year
Total vampire load: ~6,440 kWh/year
Per transformer per site * n number of sites.
If there is all three phases at the pole the cost of the utility providing a 240/139 wye bank is not what I would call major expense as your not changing voltage.
Its more just the bureaucratic hassle of seeing if they are willing.

 

[Joethemechanic]

Its more just the bureaucratic hassle of seeing if they are willing.

Yeah if the POCO is willing to foot the bill.

But if it's an open wye primary and it's a mile long, well that might be a hard sell.

I'm picturing this has to be a small plant if they are running it on 240 three. Although those aeration blowers can really use up the KWh. so maybe they use enough that the utility might eat the costs

 

[tortuga]

Yeah if the POCO is willing to foot the bill.

But if it's an open wye primary and it's a mile long, well that might be a hard sell.

I'm picturing this has to be a small plant if they are running it on 240 three. Although those aeration blowers can really use up the KWh. so maybe they use enough that the utility might eat the costs

Well yeah definitely I would not suggest it if the 3ph is not already there, if you have rural open delta, like the OP forget it. and here the wastwater district / water district pays the the utility for any upgrades.
What I was thinking of is suburban / urban setting with these largely un-attended lift stations or pump stations and 3ph right on the pole, here it was actually old 240 corner ground. I did not know if utilities could even provide 240/139 service, last summer I posted the question and @kwired had the solution to use 3X center tapped 277 cans, then parallel the windings, I am not a utility guy but you get the idea. You may not notice the little shacks and buildings but a small sized city here, somewhat flat has 48 pump stations.