theoldwizard1
Well-known member
So buildings wired for 480/277 "Y", where do the get their 120 from ? Big *** transformer ?
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Not a Sparky, just a dumb engineer
- Thread starter theoldwizard1
- Start date
MBfreak
MEMBER EMERITUS
Many 1980ish CNC machines from Japan ran on Dyn connected 3 phase 200 V on the secondary with the n point earthed.
Used adaption XF, which often had several tappings on the D. Rating 3-7 kVA. Now available for scrap price ( at least in Sweden).
Most of these machines are ruminating in "second hand " CNC places.
Go to a good place for used machinetools, and you may find the transformer that you need.
Ola
Used adaption XF, which often had several tappings on the D. Rating 3-7 kVA. Now available for scrap price ( at least in Sweden).
Most of these machines are ruminating in "second hand " CNC places.
Go to a good place for used machinetools, and you may find the transformer that you need.
Ola
sparky 1971
Well-known member
Yes. Many times if the place is big enough, there are several transformers.So buildings wired for 480/277 "Y", where do the get their 120 from ? Big *** transformer ?
dave*99
Well-known member
Warehouse at work has a 3 phase 480 panel, a transformer about the size of a dishwasher on the floor and a 3 phase 120/208 panel next to the 480 panel. Very typical arrangement.
wyliesdiesels
Well-known member
To get split phase 120/240v a dry type step down transformer served from the 480v service is neededSo buildings wired for 480/277 "Y", where do the get their 120 from ? Big *** transformer ?
For Spec Suites, we typically have either a 200 or 400A 277/480V 3-Phase 4W transformer for lighting and HVAC, plus other warehouse equipment.
We use a 75kVA step-down transformer to a 225A 120/208V 3-Phase 4W panel.
Anything other than that is a special request.
We use a 75kVA step-down transformer to a 225A 120/208V 3-Phase 4W panel.
Anything other than that is a special request.
BreeStephany
ALLIANCE MEMBER
Yes, in a building with 480/277 3ph incoming power from the utility, a breaker rated for the load of the 480V 3ph primary / 120/208V 3ph "wye" secondary transformer (transformer rated for combined 120/208V loads) is generally run from the MDP (main distribution panel) to a transformer in an electrical room and then a secondary 120/208V 3ph panel with its own main disconnect to supply all 120/208V loads.So buildings wired for 480/277 "Y", where do the get their 120 from ? Big *** transformer ?
We generally ALWAYS go with 120/208V 3ph "wye" secondary transformers to ensure that all phases are 120V to ground. The reason being is that 120/240V 3ph "delta" secondarys have a "high leg" which has a higher voltage to ground than 120V, so you have to skip that phase on the panel for 120V single pole breakers, leading to needing larger spaced panels or additional sub panels from the main panel fed from the secondary of the transformer.
It's generally good practice to keep the transformer near the MDP / main grounding point of the service and to ensure that the transformers ground it run back to the main 277/480V MDP / main disconnect to ensure that potential for noise created from the transformer is reduced as much as possible on the system, since the neutral of the secondary side of transformer is bonded to ground within the transformer.
This is the reason many buildings have a centralized electrical room near the main point of entry/main disconnect/MDP. Helps keep the cost of larger feeders to a minimum.
On buildings with 480/277V power, it's good practice to have all of the lighting loads at 277V and as many of the motor loads, inductive heat loads, etc. rated for 480V to keep 'unnecessary' loads off of the 120/208 load so that you can minimize the required size of the transformer, size of the secondary panel and size of the secondary feeders.
I know my explanation is probably a little above and beyond the scope of your question, but hope it helps.
Just my two cents.
wyliesdiesels
Well-known member
excellent explanationYes, in a building with 480/277 3ph incoming power from the utility, a breaker rated for the load of the 480V 3ph primary / 120/208V 3ph "wye" secondary transformer (transformer rated for combined 120/208V loads) is generally run from the MDP (main distribution panel) to a transformer in an electrical room and then a secondary 120/208V 3ph panel with its own main disconnect to supply all 120/208V loads.
We generally ALWAYS go with 120/208V 3ph "wye" secondary transformers to ensure that all phases are 120V to ground. The reason being is that 120/240V 3ph "delta" secondarys have a "high leg" which has a higher voltage to ground than 120V, so you have to skip that phase on the panel for 120V single pole breakers, leading to needing larger spaced panels or additional sub panels from the main panel fed from the secondary of the transformer.
It's generally good practice to keep the transformer near the MDP / main grounding point of the service and to ensure that the transformers ground it run back to the main 277/480V MDP / main disconnect to ensure that potential for noise created from the transformer is reduced as much as possible on the system, since the neutral of the secondary side of transformer is bonded to ground within the transformer.
This is the reason many buildings have a centralized electrical room near the main point of entry/main disconnect/MDP. Helps keep the cost of larger feeders to a minimum.
On buildings with 480/277V power, it's good practice to have all of the lighting loads at 277V and as many of the motor loads, inductive heat loads, etc. rated for 480V to keep 'unnecessary' loads off of the 120/208 load so that you can minimize the required size of the transformer, size of the secondary panel and size of the secondary feeders.
I know my explanation is probably a little above and beyond the scope of your question, but hope it helps.
Just my two cents.