Transformer Sizing
- Thread starter 3hots
- Start date
- Status
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
112.5KVA is the standard size for a three phase. Otherwise you will have to drop down to a 75kVA.
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
augie47 said:
Well, technically your not wrong because you could have a custom built transformer made. It's just that schedule impact and $$$ would probably force you into using one off the shelf. :smile:
- Location
- Illinois
- Occupation
- retired electrician
That would appear to require a 3 phase 4 wire wild leg delta transformer. As I recall you are very limited as the the amount of single phase 120 volt load you can place on these transformers. I think that this only applies to three phase delta/delta transformers.
Don
Don
BAHTAH
Senior Member
- Location
- United States
heating loads
heating loads
Don is correct. You state that the heating loads are 240V and 120V so I assume you are using a Mid-Tap transformer. Here is the note GE shows under the application of a Mid-Tap transformer and I have found other manufactures to have the same stated limitations. " When utilizing the 120V midtap for single-phase applications, the single-phase load should not exceed 5 percent of the three-phase kva rating. The three-phase kva load must be redduced by the same percentage as that added by the single-phase load. Additional loading beyond the 5% may cause the transformer to over heat and fail. If single-phase load is in excess of 5%, it is recommended that a separate single-phase unit be used to handle the load". Something to consider as long as your loading falls withing the 5% and the three-phase loading falls within its adjustment you should be ok. On your 112.5kva you would have about 107kva of three-phase if you used the full 5% on single-phase of 5.625kva.
heating loads
Don is correct. You state that the heating loads are 240V and 120V so I assume you are using a Mid-Tap transformer. Here is the note GE shows under the application of a Mid-Tap transformer and I have found other manufactures to have the same stated limitations. " When utilizing the 120V midtap for single-phase applications, the single-phase load should not exceed 5 percent of the three-phase kva rating. The three-phase kva load must be redduced by the same percentage as that added by the single-phase load. Additional loading beyond the 5% may cause the transformer to over heat and fail. If single-phase load is in excess of 5%, it is recommended that a separate single-phase unit be used to handle the load". Something to consider as long as your loading falls withing the 5% and the three-phase loading falls within its adjustment you should be ok. On your 112.5kva you would have about 107kva of three-phase if you used the full 5% on single-phase of 5.625kva.
- Status