Calculation for 240V/1 or 240V/2 Phase system

Status
Not open for further replies.
E

electricalintern

Member
Location
PA
Occupation
Intern in Highschool
This is my first time seeing a 240V/2 Phase breaker.

The utility company said they can provide the store with 400 amp with (2) 100:5 CT.

Does that mean the store will get (2) 200 AMP 240V/1 Phase or 400 AMP 240V/2 Phase?

I know 1 Phase has 3 wires and 2 Phase has 5 wires, but how would you add all the loads up to make sure the circuit is not overloaded.
 
2 phase is very rare and it is very unlikely you will be getting a new 2 phase service.

A 2 pole 200 amp breaker at 240 volts will support 48kVA of load. You will have to do a load calculation per Article 220 to determine the load.
 
To echo what Don stated forget about 2 phase in any new construction. Since they're providing two CTs you have single phase.
 
infinity said:
To echo what Don stated forget about 2 phase in any new construction. Since they're providing two CTs you have single phase.
Click to expand...
How many CT will they provide if the service is 240V/2 Phase?

Here is an example of the what 1 Phase and 2 Phase is available at the store

My load is around 150kva but the utility company is not providing the store with 3 Phase service.

So I was wondering what my options are with 240V/2 Phase if it will get me more power at 400 AMP.

But I don't know how to calculate the 150kva to 2 Phase.

I know for 3 Phase you do sqrt 3 = 1.73





Screenshot 2024-01-02 134822.png
 
Peco, or whatever they're called now- center city Philadelphia (and hartford CT?) are about the only places that have it.

From Peco's Metering requirements doc (2022)-
8.9.1 Two-Phase (Maintenance Only - Not for New Construction)
Obsolete equipment in Figures 8.09 and 8.10 were removed from this Revision. For
maintenance only applications acceptable equipment is listed in Figure 8.15
Click to expand...
 
electricalintern said:
How many CT will they provide if the service is 240V/2 Phase?

Here is an example of the what 1 Phase and 2 Phase is available at the store

My load is around 150kva but the utility company is not providing the store with 3 Phase service.

So I was wondering what my options are with 240V/2 Phase if it will get me more power at 400 AMP.

But I don't know how to calculate the 150kva to 2 Phase.

I know for 3 Phase you do sqrt 3 = 1.73





View attachment 2569339
Click to expand...

That sure looks like the PECO S&M form. I don't think they will give you a new 2Ø, 5W service - only upgrades like zbang said. If you do get a 2Ø service, it's a good idea to put a scott-connected transformer right after the main and feed everything with conventional 3Ø equipment.

Your 150 kVA will draw 312.5A on the two-phase side. The calculation is I = S/(2 x V) = 150,000 / (2 x 240). Here's a couple of pages from an old Electricians Handbook 9th ed. (c) 1970... (The electrician who gave it to me worked at Philadelphia Navy Yard.)

1704295739864.png

1704295767859.png
 
Note that 120/208 3 phase is checked in the example. I do not think anyone will give you a new 2 phase service

You can measure 3 phase with just two cts iirc, but I think it only works on Delta systems.

I think your choice is going to be 120/240 single phase or 120/208 three phase.

From your description, it sounds to me like they are offering you 120/240 single phase 400 amps. That would be almost 100 kva. Lots of power.

However that does not match up to 100:5 cts.
 
Status
Not open for further replies.
Top