installed a 30 hp single to three phase converter today,dummy me did not look at the power co transformer on the pole, it is rated 15kva,converter needs at least 40kva it is a bussiness service,it trips the jack on pole upon start-up,power co wants him to put a 3 phase service in and does not want to up size the transformer,now what any ideas?
30 hp 230 volt phase converter
- Thread starter mdh
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texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
Wouldn't a VFD also be more efficient?
His current converter is 30hp, which is 22.4kW. Compared to 40kVA input, that's not very efficient.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
Don't know which would be more efficient, but I think the issue here is the huge inrush on a single phase supply.
I also just noticed that I said single phase motor in my previous post. Obviously, I meant 3 phase but I think you got that. I should have been more specific and said 3 phase motor fed from a single phase source.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Not really clear enough to be able to help much. Are you running one motor off of that phase converter? Is it a 30HP motor? Or is the phase converter using a 30HP pony motor and the load connected to it is less than that?
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Who decided to buy the converter before finding out what it would take to have three phase service? Sometimes it seems POCO may want a lot to get you the service you need, but conversion equipment is not cheap either, and then you find the existing supply is not enough anyway.
Even if they had a larger existing transformer, you still may have had problems - 40kVA wipes out most of a 200 amp single phase service, and you still have to power whatever is existing. Chances are if larger transformer it probably supplies multiple customers and maybe you still added too much.
Sorry but someone dropped the ball here.
Even if they had a larger existing transformer, you still may have had problems - 40kVA wipes out most of a 200 amp single phase service, and you still have to power whatever is existing. Chances are if larger transformer it probably supplies multiple customers and maybe you still added too much.
Sorry but someone dropped the ball here.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Why doesn't he want to subscribe to three phase service from POCO? Sounds like that should have been something discussed very early in the planning stage here. Phase converters are ok for an occasional small load or out in middle of nowhere where miles of line need run to be able to get three phase. Even an open delta supply is preferred to phase converters especially for motors as large as 15-20 HP or more.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
If his entire facility needs 3 phase and he has a 25HP motor, he needs to get 3 phase power. But he probably found out that with 3 phase power comes a demand meter, which will usually result in additional energy costs to him. So he is attempting to remain on a single phase light commercial service with no demand metering. But utilities only provide that type of service to residential customers and the smallest of commercial users, such as stores and small offices that don't have large machinery, because the overall net effect of those is relatively small enough for them to manage. Once a user goes over a certain threshold of power use, they need to know what the demand is and they want to get reimbursed for the associated cost of providing it. A very common way of detecting that change in use is when a customer requires 3 phase power. Phase converters thwart that to a certain extent, but for the most part, they are small and inconsequential. He is using a 30HP phase converter, they are saying no way.
Utilities have rules, he is trying to circumvent them, they know it, they are not cooperating. He is forgetting though that they have the power, Literally.
Utilities have rules, he is trying to circumvent them, they know it, they are not cooperating. He is forgetting though that they have the power, Literally.
agreed! he did not ask for advise before buying this,meeting with poco tomorrow
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Unless this guy only has limited times when he runs this equipment the proper supply from the utility is what is going to cost the least in the long run. It is one thing to run a few hours every week or month, then a generator may be worth using, but if he is loaded daily POCO is really not that expensive to operate on compared to most alternatives.
Don't muddle power factor with efficiency.
Certainly poorer power factor will increase some losses. But you can't compute one from the other directly.
A VFD might be more efficient but I'm not quite sure what exactly is being proposed - a rotary set maybe?
I might have missed some information and more than a few posts but it seems to me that a 15kVA single phase transformer just ain't gonna hack it.
I'm not. The use of 'efficient' isn't limited to the engineering definition, even in a technical discussion. But if it'll make you feel better, you have my permission to mentally substitute the word 'effective'.
But
does read that way.
Given that this is an electrical forum, I think we should endeavour to use the terms correctly.
And I did use the term correctly. If you read it otherwise, that is your problem, especially now that I have clarified the sense in which it was used. In further support of my position, note I used the term efficient... and made no reference to the term efficiency.
JoeStillman
Senior Member
- Location
- West Chester, PA
The efficient thing to do would have been to hire a consulting engineer before buying any equipment.
Chill!!
Something can have a poor factor and still be quite efficient. For example, I have a 325kW output motor that takes 420kVA. By your reckoning it would not be very efficient but, at 96%, I would consider it to be quite efficient. You simply can't judge from the kW and kVA how efficient something is. But that's what you did.
Anyway, the bottom line for the OP is that the 15kA tranny isn't big enough
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kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
The owner engineered it himself
Now the OP has to make it work, even if using a real engineer would have been more economical in the long haul. Probably all or mostly all used equipment that was a good buy on top of everything - been there before. Some people can't understand why it cost more to connect the used equipment than they spent on it, then it cost a lot to maintain after they get it running, or was just a little too small for their real needs:slaphead:
T
T.M.Haja Sahib
Guest
I do not know why the POCO refuses to enhance the service of the OP to higher capacity, since up to 144 KVA or at least 96 KVA single phase service may be provided by the utility per the link below.
http://www.assocpower.com/index.php?Single-Phase-Power
http://www.assocpower.com/index.php?Single-Phase-Power
Give it a rest. The system is ineffective. Move on!!!
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