4 Wire Wye Vs 4 Wire Delta - New Construction

[kwired]

This to support what I said. I swear, DC is the future of power transmission.



http://www.think-grid.org/dc-system-systems

If it is, I don't see it happening during my lifetime - in my region anyways.

 

[cre8er]

OK so the Power company is coming out tomorrow and they gave us the options:
120/208Y
277/480
120/240 Delta

Since most of our motors are calling for 460 volts a 208Y or 240 Delta system will not work will they?
How will I get 120V if I go with a 277/480v 3 phase system?
They are coming out tomorrow to run the lines on the poles.

 

[Smart $]

OK so the Power company is coming out tomorrow and they gave us the options:
120/208Y
277/480
120/240 Delta

Since most of our motors are calling for 460 volts a 208Y or 240 Delta system will not work will they?
How will I get 120V if I go with a 277/480v 3 phase system?
They are coming out tomorrow to run the lines on the poles.

Well if you only get one service (some POCO's will give you two of different configuration), you'll have to use a transformer to get the "other" voltage.

If they offer only one of the three, I'd go with 480/277.

 

[GoldDigger]

OK so the Power company is coming out tomorrow and they gave us the options:
120/208Y
277/480
120/240 Delta

Since most of our motors are calling for 460 volts a 208Y or 240 Delta system will not work will they?
How will I get 120V if I go with a 277/480v 3 phase system?
They are coming out tomorrow to run the lines on the poles.

Given any kind of three phase service and the need for more voltages than one service can provide your, electrical contractor has two choices:
1. Send 480 directly to your motors and install step down transformers for everything else.
2. Send 208Y/120 to your lighting, heating and small motor loads and provide step up transformers for your large motors.
The design decision will depend on the relative amount of the two types of loads among other things.

The 120/240 delta system is slowly going out of favor for various reasons and you may not want to go there for future compatibility.

 

[kwired]

The 120/240 delta system is slowly going out of favor for various reasons and you may not want to go there for future compatibility.

In general that is probably true. There are still areas where there is a lot of 120/240 delta, both new and old services. Outside the open delta systems that have other conveniences for the POCO, a full delta with three equal size transformers is still popular around here when the majority of the load is motors.

If there is a lot of 120 volt load the 208/120 system gets more preference.

 

[cre8er]

Thanks for the replies.
We went with 480/277. Just to make sure this will be a WYE configuration correct? Is there 480 Delta?

Guess we have to look at something like a 100 amp 120/240 transformer for the normal loads as they wouldn't give us both.
Are these usually put in a CT box on the wall next to the load center, or outside?

We had already bought a 208Y load center thinking we were going to go that way. I'm pretty sure it won't work for 480Y.

 

[GoldDigger]

Thanks for the replies.
We went with 480/277. Just to make sure this will be a WYE configuration correct? Is there 480 Delta?

Guess we have to look at something like a 100 amp 120/240 transformer for the normal loads as they wouldn't give us both.
Are these usually put in a CT box on the wall next to the load center, or outside?

We had already bought a 208Y load center thinking we were going to go that way. I'm pretty sure it won't work for 480Y.

If you get a transformer to get 120/240 it will have a single phase secondary and will necessarily not present a balanced load on the service.
This is not necessarily a bad thing as long as the imbalance is not too large or POCO does not care.
Or you can transform to 208Y/120 three phase, often used in commercial settings.

 

[Smart $]

Thanks for the replies.
We went with 480/277. Just to make sure this will be a WYE configuration correct? Is there 480 Delta?

Guess we have to look at something like a 100 amp 120/240 transformer for the normal loads as they wouldn't give us both.
Are these usually put in a CT box on the wall next to the load center, or outside?

We had already bought a 208Y load center thinking we were going to go that way. I'm pretty sure it won't work for 480Y.

How are you going to handle the 480V loads? You mentioned motors. How many? What HP? MCC with a service disconnecting means front end? The reason I ask is because you can get an MCC with a step-down transformer and a 208Y/120V load center built in.

Given you already have a 208/120 load center, you may just want to opt for a floor or housekeeping pad mounted dry-type step-down transformer between 480V and 208V gear.

 

[kwired]

Thanks for the replies.
We went with 480/277. Just to make sure this will be a WYE configuration correct? Is there 480 Delta?

Guess we have to look at something like a 100 amp 120/240 transformer for the normal loads as they wouldn't give us both.
Are these usually put in a CT box on the wall next to the load center, or outside?

We had already bought a 208Y load center thinking we were going to go that way. I'm pretty sure it won't work for 480Y.

480/277 is derived from wye connected source. There is 480 volt delta but is physically impossible to get 277 from it without additional transformation equipment.

You will need additional transformer(s) to get 120, 208, 240 or combinations of those values, both single or three phase.

You will need additional panel/switch gear rated at least 480 volts for the 480/277 distribution portions of your equipment.


Don't take this wrong way, but if you didn't know some of what I just mentioned maybe you are in over your head on this.