Re: CT Reference Voltage
Posted: Tue Aug 02, 2016 4:18 pm
Im not sure to be honest. I have not found ohms to be a reliable method of determining if a CT is bad or not.
Here is a little experiment that I just conducted on 3 of the BCT-015-200 and 3 of the BCT-025-200 Current Transformers in ohms. These are new out of the drawer:
BCT-015-200:
580 ohms
564 ohms
582 ohms
BCT-025-200:
580 ohms
564 ohms
582 ohms
I do not know what these results mean they were taken on an old Fluke 8840A for your reference.
I would test your CTs using the Omnimeter, you can connect all 3 CTs to the same Primary Current line and connect all 3 voltage inputs together with jumpers. That way all 3 inputs are seeing the same voltage and all 3 CTs should be measuring the same current. You can then look at the watts on each line. I would do this on a steady 100 watt load, a steady 1000 watt load, and a steady 5000 watt load. Let me know what you get. If there is something that jumps out as being odd you can swap CTs inputs around to see if the anomaly follows the CT.
Just a heads up for you and others that are reading this. One way you can damage a CT is if it is connected to a primary wire and the secondary wires of the CT are either not connected to a meter or they are not shunted together. You should always shunt the CT white wire to the black wire if you are going to leave the CT connected to a primary wire with current in it.
Here is a little experiment that I just conducted on 3 of the BCT-015-200 and 3 of the BCT-025-200 Current Transformers in ohms. These are new out of the drawer:
BCT-015-200:
580 ohms
564 ohms
582 ohms
BCT-025-200:
580 ohms
564 ohms
582 ohms
I do not know what these results mean they were taken on an old Fluke 8840A for your reference.
I would test your CTs using the Omnimeter, you can connect all 3 CTs to the same Primary Current line and connect all 3 voltage inputs together with jumpers. That way all 3 inputs are seeing the same voltage and all 3 CTs should be measuring the same current. You can then look at the watts on each line. I would do this on a steady 100 watt load, a steady 1000 watt load, and a steady 5000 watt load. Let me know what you get. If there is something that jumps out as being odd you can swap CTs inputs around to see if the anomaly follows the CT.
Just a heads up for you and others that are reading this. One way you can damage a CT is if it is connected to a primary wire and the secondary wires of the CT are either not connected to a meter or they are not shunted together. You should always shunt the CT white wire to the black wire if you are going to leave the CT connected to a primary wire with current in it.