grounded B phase schematic

[wrasmussen]

I need a good, simple schematic for the grounded B phase configuration for demonstrative purposes. Any help will be appreciated!

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[ April 13, 2005, 10:20 AM: Message edited by: charlie b ]

 

[ronaldrc]

Re: grounded B phase schematic

Here is one of Eds diagrams I had in my library.
Please copy it for future reference. Hope you don't mind Ed.

 

[charlie]

Re: grounded B phase schematic

I never cease to be amazed at how well Ed's drawing are made. They are simple, clear, easy to understand, and easy to read.

 

[scott thompson]

Re: grounded B phase schematic

Check out this information at ECN, under the topic heading of:

Corner Grounded 3 Phase 3 Wire Delta

Direct link is:
http://electrical-contractor.net/ubb/Forum15/HTML/000078.html

Scott

 

[friebel]

Re: grounded B phase schematic

I would like to pass this information on, concerning Delta transformers, with B-Phase grounded.
I worked for a large Chemical Company and at the plant-site that I worked, our Primary voltage to our sub-stations was 11KV. The Secondary voltage was 600 Volts, Delta Connection with B-Phase grounded.
On the secondary of our transformer we fused A and C Phase, and B phase we put a copper bar in place of a fuse.
Let me give you an example of how this stopped the single-phasing of our three-phase motors which were 575 volt.
The primary voltage of a control transformer in the individual starter fed from A and C phase. Now this meant that if a fuse would blow on A or C phase, in the individual motor starter, our control transformer for that starter would de-energize, therefore the motor would shut-down. Hence, we would never had single-phasing of our three-phase motors.

 

[iwire]

Re: grounded B phase schematic

Originally posted by friebel:
On the secondary of our transformer we fused A and C Phase, and B phase we put a copper bar in place of a fuse.

As this system had B phase intentionally grounded 240.22 prohibits installing overcurrent devices on B phase.

There are some exceptions.

 

[friebel]

Re: grounded B phase schematic

Good morning iwire, Bob Bader, I am glad that you informed me of 240.22. I looked it up and yes, you are correct about not installing an overload in B-phase, but as you mentioned, there are some exceptions, and one of them refers you to 430.36 or 430.37.
At our plant site, we always had our three-phase starters supplied with overloads in all three phases.
I can remember, when I was a young apprentice boy, that we always had plenty of three-phase motors that had single-phased, but after we went to the Delta-connected transformer with the secondary of B-Phase grounded, that solved our single-phasing problems with three-phase motors,by the way we connected the primary of the control transformer in the individual motor starter.