Hi, I want to measure a precise number of leakage current in the 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?