current transformer taps

[ajengin]

how many taps can the main current transformer feed for example main ct into 4 MDP's.

we have an overhead electrical wire into the building, which feeds into the meter and feeds into a current transformer. From this transformer tapped 3 times into 3 MDP's.

please help.

 

[templdl]

Re: current transformer taps

This post has been sitting here a while so I'll take a shot at it.
CTs are commonly series connected, that is from the CT to the device to the next device to the next device and back to the CT. So the word "tap" appears to imply a parallel connection which is not the way CTs are wired.
CTs essentially must be shorted when wired. They never are to left open circuited.
As you add another device in series that device would add a small amount of resistance to the series circuit and affect the current flow to all devices by reducing it slightly.
I don't have my CT stuff handy but as I can recall there are various CTs that are C100, C200, C400, etc, which may need to be a consideration when which one to selecting a CT for the application. Its been about 10 years since I dealt with the stuff.

 

[Ed MacLaren]

Re: current transformer taps

ajengin,
Were you referring to an instrument CT, similar to the sketch below, or to a power transformer?

Ed

 

[ajengin]

Re: current transformer taps

power transformer

 

[templdl]

Re: current transformer taps

Ah, a power transformer (or CPT?). Then you're looking for control power or power?
120vac? If so you're going to have to determine the va required for each load to determine if the CPT has the capacity.
Your reference to

...and feeds into a current transformer. From this transformer tapped 3 times into 3 MDP's.

is somewhat vague at best. What va is the CT which now appears to be a

power transformer

CPT? And what are the power requirements of the

tapped 3 times into 3 MDP's

?
So, your question of

how many taps can the main current transformer feed

is going to depend upon the VA of the CPT (power transformer) and the load or va required for each.

 

[Ed MacLaren]

Re: current transformer taps

For an EE, ajengin seems to be "a man of few words".

I think he must mean feeders to distribution panels. He referred to 3 MDPs, and also to 4 MDPs.

He may be asking if an additional panel feeder can be added.

Ed

[ February 24, 2005, 06:47 PM: Message edited by: Ed MacLaren ]

 

[templdl]

Re: current transformer taps

He may be a man of few words but it would be nice if would use more we could use less. All too often we it ends up to be a guessing game.