Hi,
I am working on a project and I was trying to find some information regarding how to power devices inductively off of a power line. The lines will be 100A +- 50A and anywhere between 4kV to 12kV. What I am building will be clamped around the line. I am looking to make a 9VDC power supply to power a device and also to charge a battery.
I was able to find this post regarding a similar idea. http://forum.allaboutcircuits.com/showthread.php?t=2688
My first thoughts were to use some coils placed near the line to induce some voltage a la Faraday's law. However, a lot of turns were required to do that. I am now considering using a CT like device around it.
I am just looking for some insight into this. A CT has a burden or some type of load across it, never open circuited so to prevent huge voltage differences. I guess what I'm wondering is how to get the voltage I want out of the secondary. A 100:5 CT will give me 5A at normal current, is this regardless of the line voltage? If I put the same CT on a line with half as much voltage, will it still deliver 5A on the secondary with a 100A primary?
The reason I ask is because the power transfer doesn't quite make sense to me. 12kV 100A primary put through a 100:5 CT with a 1 ohm load will have 5A and 10V across the secondary. Why is the voltage not 240kV as expected from a 100:5 ratio? This seems to ignore power transfer equation for transformers. Am I to model the secondary as a perfect dependent current source?
In reference to the link I posted, the poster mentioned putting a diode bridge with cap and zener to create his power supply. My only question is how would he determine the voltage input to the bridge? If he needed a 3VDC output, he'd need around 5-6 VAC peak to generate it. If the power supply is to load the secondary windings, I don't see how to set an input voltage.
Sorry about the long post, but thanks in advance to everyone.
I am working on a project and I was trying to find some information regarding how to power devices inductively off of a power line. The lines will be 100A +- 50A and anywhere between 4kV to 12kV. What I am building will be clamped around the line. I am looking to make a 9VDC power supply to power a device and also to charge a battery.
I was able to find this post regarding a similar idea. http://forum.allaboutcircuits.com/showthread.php?t=2688
My first thoughts were to use some coils placed near the line to induce some voltage a la Faraday's law. However, a lot of turns were required to do that. I am now considering using a CT like device around it.
I am just looking for some insight into this. A CT has a burden or some type of load across it, never open circuited so to prevent huge voltage differences. I guess what I'm wondering is how to get the voltage I want out of the secondary. A 100:5 CT will give me 5A at normal current, is this regardless of the line voltage? If I put the same CT on a line with half as much voltage, will it still deliver 5A on the secondary with a 100A primary?
The reason I ask is because the power transfer doesn't quite make sense to me. 12kV 100A primary put through a 100:5 CT with a 1 ohm load will have 5A and 10V across the secondary. Why is the voltage not 240kV as expected from a 100:5 ratio? This seems to ignore power transfer equation for transformers. Am I to model the secondary as a perfect dependent current source?
In reference to the link I posted, the poster mentioned putting a diode bridge with cap and zener to create his power supply. My only question is how would he determine the voltage input to the bridge? If he needed a 3VDC output, he'd need around 5-6 VAC peak to generate it. If the power supply is to load the secondary windings, I don't see how to set an input voltage.
Sorry about the long post, but thanks in advance to everyone.