Have someone tried 'Talema AZ Series' CTs?


#1

Hi,

I’ve been using IotaWatt for a month and I’m very happy with it :smile: I started using a couple of SCT-006-000 and SCT-013-000 in a temporary setup just to play around with it.

I was searching for solid core CTs and I came across to these: Talema AZ Series
Have someone tried this type of CTs?

They are available at Mouser/Digikey/RS for a reasonably low price (~3-5€ each), so I bought one of each type (AZ-0500, AZ-0750, AZ-1000) to measure the energy generated by my photovoltaic inverter and compare them with the other CTs that I have.

Right now I’ve configured in IotaWatt three generic input channels selecting the proper number of turns (500, 750, 1000), but I left “Phase lead” parameter to 0.00, how can easily I determine the correct phase shift values for these CTs?


#2

To answer your question:

  1. You can send me a couple and I’ll test them.
  2. You can measure the shift with your IoTaWatt vs. your VT.

For option 2:

Install the CT on a conductor that will carry at least several amps. Loop the conductor through multiple times to multiply it if necessary.

Apply a purely resistive load. Incandescent light bulbs are good. Toasters are good.

Use the browser command: http://iotawatt.local/command?vtphase=INPUT where INPUT is the input channel of your CT.

If you get a large number, reverse the CT or the VT and do it again. I would guess that a CT like that will be less than 1. Add the result algebraically to the configured VT shift to get a reasonable shift value for the CT.

Shift varies with current, so there is no perfect answer, but with solid core CTs it’s usually low and behaves well at the low end. Nevertheless, try to do it at the typical current the CT will be asked to measure.

Couple of other things:

Those CTs don’t appear to have TVS diodes, so be careful not to energize the primary without shorting or connecting to the IoTaWatt.


#3

Thanks for the detailed response @overeasy :blush:

From what I’ve read in this forum, you should live in the US, I live in Italy and a shipment of a small packet would cost way more than the actual values of these CTs. I’d prefer to fund you directly in order to buy those CTs even others to improve the overall IotaWatt product.

That’s a really nice feature, I’ll do some test in the weekend and than post here the results.
Right now I’ve collected some data of the production of my photovoltaic inverted, it generates with a power factor of almost always 1.0, yesterday the energy measured by CT that I’m using was

  • SCT-006-000: 10.661 kWh
  • SCT-013-000: 10.710 kWh
  • AZ-0500: 10.466 kWh
  • AZ-0750: 10.552 kWh
  • AZ-1000: 10.512 kWh

These results are with phase shift configured to 0 for Talema’s CTs.

That’s correct, no TVS diodes built in. Thanks for reminding me about that.


#4

That’s probably close to what it is. Solid core CTs can be .1 to .3. The small variation really doesn’t matter when you are dealing with unity PF (1.0). It only matters with highly reactive loads.

Those results are pretty consistent. 3 significant digits is about as accurate as you should expect (<1%). In several installations I get the same result with HWCT-004 solid core CTs on Solar Inverters. The kWh are consistently within 1% of the energy reported by the (solar edge) inverters.

I would put these CTs in the same category as HWCT004 and DL-CT08CL02. I do think the echun ECOL09 is slightly better, has TVS diodes, can do 50Amps, and comes with a long cord and 3.5mm jack.


#5

Hi Bob,

I also have a question about this: if I do this for an ECS24200, I get the following numbers:

Channel: 12
Refchan: 0
Measured shift: 25.31 degrees
Artificial shift: 28.12 degrees (60) samples
Net shift: -2.81 degrees

Is net shift the size I’m looking for? As voltage reference I use an Ideal 77DE-06-09(EU) with a phase lead of 1.78. If I add the two numbers I get about -1?

I know that the phase lead for the ECS24200 is already available, but I’m trying to find the right number for an ECS24400.


#6

The shift in the tables for the VT was done at 240V 60HZ. That was before I had a 50HZ capability. Also, the shift for the ECS24200 is at 60HZ. So I’ll get you better numbers at 50HZ. The ECS2420p is very low shift anyway, so I don’t think you are that far off, but right, I don’t think it lags.

I can’t do this until middle of next week, but before then, can you tell me what the current was when you tested this? The phase shift of the CT will vary with that.


#7

Thank you Bob, that would be great!
The current was 12.45 A (fan heater and toaster together).


#8

If it is not too difficult, the factors for SCT0013, SCT006, SCT0019 and Ideal 77DE-06-09(EU) at 50 Hertz would also be very interesting.


#9

The SCT006 is a waste of time because phase shift is all over the place. I have also now realized that I don’t have a 77DE-06-09 Euro AC adapter. I have the D8-06-09 UK adapter. I will test that but it may be quite different from the EU adapter. I have SCT013 and SCT019.