generator for a building fed with a delta "feeder"

Status
Not open for further replies.

mshields

Senior Member
Location
Boston, MA
I've got a university campus building, the campus primary metered, with a utility like feeder, i.e. off a pole line with a delta feeder to the building. The owner wants to add a generator for the entire building (it's pretty small). Do they make generators with delta output and regardless of that, is my best bet to provide a normal generator with a delta/wye 1 to 1 transformer?

Thanks,

Mike
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Or to phrase it more explicitly, is one of the delta windings center tapped to provide both 120 and 240?
Also known as high leg delta?
If so you will typically need to add your own transformer to one line-to-line connection to get you 120 circuits if the generator is three wire delta.

Tapatalk!
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
I've got a university campus building, the campus primary metered, with a utility like feeder, i.e. off a pole line with a delta feeder to the building. The owner wants to add a generator for the entire building (it's pretty small). Do they make generators with delta output and regardless of that, is my best bet to provide a normal generator with a delta/wye 1 to 1 transformer? ...
Shouldn't need a transformer

What's the voltage, out of curiosity? Is it a 3-wire delta or 4-wire?
Yes, this will matter as well as the required power.

For example, 2400V delta will be more difficult. If you don't want to wait for the gen to be wound - you may need a transformer.

480V delta should be available.

And multiple megawatts may take a while.

Or to phrase it more explicitly, is one of the delta windings center tapped to provide both 120 and 240? ...
You will be able to get/order a 12 lead gen that can be connected for 240/120 4W.

ice
 

mshields

Senior Member
Location
Boston, MA
to answer your questions

to answer your questions

It's center tapped so yes it does give them 240V. One of the comments above asserted that a center tap would give one 240 and 120V. How so. From my understanding one of the legs of the triangle would be center tapped (say between A and C) such that one could get from this distribution panel: 480V 3 phase (obviously), 480V single phase (from A to B or B to C), and 240V (either from A to the center tap or from C to the center tap).

Am I missing something. I confess to never having dealt with one of these.

Also, my Cat rep was quick to tell me that a the lead time would be quite long but maybe there are other vendors more flexible. Any suggestions?

Thanks,

Mike
 

__dan

Senior Member
There may be an easy way to do it.

I would look at it to see if the single phase 240v loads are small compared to the 480v 3 phase and 480v single phase loads. If so, it may be easy to separate out the single phase 240v loads, the loads that use the service supplied center tapper neutral, and supply these with their own 480 to 240/120 transformer.

Essentially, it may be easy to convert the service supplied loads to all 480v single and three phase, then the genset would be a standard 480/277 Y output, 3 pole transfer switch, no neutral connected loads at the service or generator, with all 480v delta loads. Only the loads that need 240/120 would have their own transformer, SDS with neutral, downstream of the transfer switch and DP panels.

This also has the advantage that loads downstream of the smaller transformer will have a lot less available fault current instead of coming straight off the service.
 
Status
Not open for further replies.
Top