Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Measuring leakage current in 3-phase system with current transformer

Status
Not open for further replies.

Gordon01

Newbie level 2
Joined
Dec 1, 2016
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
23
Hi I want to measure precise number of leakage current in 3-phase trace heating system.
The problem I faced is that typical current transformer gives a very high error at small currents. I found some solution either to use larger core or to apply some active compensation to pre-magnetize core.
I think it is easier to pre-magnetize core because I have tight space requirements for the device, so larger core simply will not fit.
But I can't find information about pre-magnetization. The only thing I know is I need to apply the voltage with same or 3 times frequency.
In some industrial device, that does the same function I found two secondary windings, obviously one for pre-magnetization and one for measurement.

Can somebody help me with this questions:

1) What type of waveform do I need to apply to additional secondary winding?
2) What parameters of additional secondary winding
3) Can I use same core?

808ecm13fig4.gif
 

Hi,

a typical current transformer is for some Amperes, but I assume you only need to know about milliamperes.

--> Because the usefull input current range is very low, you should use a couple of primary windings to get higher secondary signal.
Maybe increase the burden resistor value.

Klaus
 

Hi,

a typical current transformer is for some Amperes, but I assume you only need to know about milliamperes.
Yeah, something in range of 10-300 mA

--> Because the usefull input current range is very low, you should use a couple of primary windings to get higher secondary signal.
Maybe increase the burden resistor value.
Due to construction limitations, it is not possible to increase primary windings.
And increasing burden resistor value doesn't help: insufficiently magnetized core has very poor current transfer performance :(
 

Referring to you original question, a possible configuration to reduce errors by non-ideal core is a compensating feedback circuit that zeros the total flux.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top