Hi everyone,

I am currently designing a Resin Cast Current Transformer and am looking for advice on the best core/winding configuration to achieve a dual output for both metering and protection.

Here are the specifications:

• Type: Resin Cast Current Transformer
• Ratio: 5000/5+5 A (Dual Secondary)
• Accuracy Class: 0.2
• ID (Window Size): 90mm x 250mm (Rectangular)
• Frequency: 50 Hz
• System Voltage: 0.66/3.0 kV
• Rated Burden: 15VA

The Design Challenge: I need a 4-terminal output where one set of terminals provides 5A for metering and the other provides 5A for protection.

My main question regarding the construction is: Should this be designed using a single magnetic core with two separate windings (insulated from each other), or is it strictly necessary to use two separate cores (one for metering, one for protection)?

I am concerned about the potential for magnetic interference or saturation issues if a single core is used for both applications, given the different saturation requirements for metering (low FS) vs. protection (high ALF). Any insights on the best practice for this specific geometry and ratio would be appreciated.

 

I know CT very well. I do not understand "protection". Maybe I have a different vocabulary.
Please post pictures or a link to the core and bobbin.

It looks like you are building a 1000:1 transformer.
Do you want 5 amps on each output? What is the input current? 5000A?

 

Obtaining accuracy at both ends of the range could be a challenge. But I anticipate that the bigger challenge will be with the % amp portion when the current is 5000 amps.

 

you cannot have 2 outputs in the way you describe - you have one output and run it through the protection and the metering - the sensible way - or you have 2 x CT's
Have you chosen a good low loss toroidal core ?