High Amperage CTs


CCI have received a couple of high amperage CTs for phase correction testing. As I understand it, these are custom ordered Echun ECS24xxx series CTs, so they have the same form factor as the ECS24200 that I sell for use on US mains. I like these CTs because they are easy to install, are purpose matched at 4000 turns (200A), and because they not only have low phase shift, it is stable within a narrow band.

The objective is to determine the proper phase correction at both 50Hz and 60Hz. Because these are very high current CTs, I have ordered some additional equipment and will soon add a higher turns multiplier to my test rig. For now, I thought I’d publish the preliminary 60Hz results at <60A because I think it is useful.

First, here is the phase shift of the ECS24200 that I make available for US 200A mains:

As you can see, this supports the 0.3° correction in the IoTaWatt device tables. Now here are the ECS24300 and ECS24400:

So based on this sample, I’d be inclined to use 0.40° for the ECS24300 and 0.35° for the ECS24400. At 60Hz. But really, 0.1° difference is almost insignificant, and phase shift this low is typically of solid-core CTs. I can get that much variation from sample to sample with the ECS24200. Compare these with the YHDC SCT019-000 at 60Hz:

We use 2.0° shift for these. The amount of shift isn’t as important as the variance. Here the CT varies between about 2.5° at 1% of range and about 1.8° when it settles in. That’s a variance of about 0.7°. The ECS24xxx vary about 0.2°. So with a single correction factor applied to all current measurements, the ECS24xxx appears to be a bit more stable.

It will be interesting to see what happens at 50Hz, and when I add a larger turns bundle to test at 200+ amps.

The rig: