Yes but that would probably involve changing a lot more than just the transformer. Without knowing more about the supply you don't know how far back upstream kit would need to be beefed up or what other knock on consequences there could be. And maybe that's what's behind the POCO's decision.
30 hp 230 volt phase converter
- Thread starter mdh
- Start date
- Status
I don't know about that either.
I'm assuming that it is a rotary frequency converter set with a single phase 30hp drive motor in which case the 40kVA transformer rating might be the minimum required to start the drive motor and may run significantly below that under steady state conditions. I don't have much experience of single phase motors and none at all at that rating so thus can't judge what the starting current might be nor what available methods there are for mitigating starting currents.
And, if it is a rotary converter, then I do agree with your point that a solid state inverter would be more efficient, considerably so, even if you had to use a transformer to get the right voltage. A variable frequency drive might fit the bill quite well depending what kit is hanging on the end of the three phase supply. If there are any controls associated with the motors the customer wants to run the controls might not take kindly to a variable voltage variable frequency supply.
But there would still be the supply capacity limitation. The15kVA simply isn't anything like enough. Even with solid state conversion.
I'm not sure about the capacity of a 30hp converter either. I think that could be a bit marginal considering that the customer has a 25hp motor according to the OP.
As it is now, it does not function at all. So let me assure you... IT IS ineffective!!!
Quite.
I was going to add "Assuming a supply of sufficient capacity, in what way would it be ineffective?" in relation to your 40kVA/22.5kW point.
But, it seemed inappropriately confrontational, so I removed it.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
In addition, most PoCos here have a requirement to keep on hand a ready supply of every size transformer they use in service drops. It could very well be that this PoCo has decided that no single phase service will be more than 15kVA, so they are not going to go out and buy 2 x 50kVA transformers (one for him, one for back up stock) just to serve and support this one user. It's their perogative.
Yes, I can see that from the POCO's POV.
I'm inclined to the opinion that the customer should stop faffing around trying to work off single phase and accept that a three-phase service is the practical way to go.
Energy charges might be more but would be offset, or would have been, by the capital cost of a the converter and its energy losses.
I don't where the break even point would be even if the supply had the capacity to support his requirements.
What does seem clear is that the customer did not take that, or the practicalities into account, before splashing the cash on a bit of kit totally unsuited to his operations.
kwired
Electron manager
- Location
- NE Nebraska
Nobody said they refuse to provide an enhanced service, it was mentioned they refuse to supply the type of load involved here from a single phase service. Most POCO will not upgrade the equipment for free - which apparently is what the owner in this case is trying to avoid by providing the phase converter, but he still has too much load for the existing source to be able to supply:slaphead:
I find it a little hard to believe many POCO's have a max of 15kVA for single phase services. I could understand 37.5 or 50 maybe, but there are many around bigger than that also - especially out in rural areas. You don't see too many larger than 50 mounted on a pole, but there are occasional exceptions.
T
T.M.Haja Sahib
Guest
It is hard to believe that the POCO would refuse to supply on the basis of type of load involved anywhere. Sloppy wiring, continued failure on the part of the user to rectify wiring defects etc., are some of the valid reasons for the POCO to refuse supply.
kwired
Electron manager
- Location
- NE Nebraska
Although in the OP's case this is not really that large of a service, but is getting close to the point where POCO would rather have supplied by three phase just because it balances the draw on the phases. Again it is not that they will not supply this customer, they just would rather see the customer utilize all three phases with this load, and customer is too cheap to upgrade equipment to do so, even though what he has done may cost more in the end.
T
T.M.Haja Sahib
Guest
I dare say your statement is not in line with the spirit of your National Electrical power distribution.
.Single phase power distribution is predominant power distribution compared to Europe. Single phase high voltage lines are extended into many areas so that single phase low voltage service connections can be readily availed. As for the limit for the size of low voltage single phase service, it is at least 96 KVA.
Last edited:
kwired
Electron manager
- Location
- NE Nebraska
I dare say your statement is not in line with the spirit of your National Electrical power distribution.
Single phase power distribution is predominant power distribution compared to Europe. Single phase high voltage lines are extended into many areas so that single phase service connections can be readily availed.
I am very well aware of this, as I live in area where there are many services that are somewhat isolated and may have miles of single phase line supplying them. There is also reality of once you go beyond a certain KVA you and POCO are probably better off with three phase supply instead of single phase supply, even to be supplied with open delta has some advantage compared to just single phase.
It is no different if a large facility decides to build in an area where sufficient power is not available, some infrastructure must be built to be able to supply them. A facility that uses a large amount of power - will have a better return on the investment as they use a lot of power. A small facility that needs to be able to be supplied with a peak demand but only for limited times will have a much lower return on investment, POCO is going to make them pay for more of the infrastructure necessary to support them, that is simply business decisions, and not what can be done or what is deemed right by any particular individual.
- Status