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Ordered SCT-013-000 but received SCT-013-000V


I recently ordered the SCT-013-000 but received SCT-013-000V by mistake. From the product range I see this is the difference:

SCT-013-000 Primary AC current: 100A Secondary current: 50mA
SCT-013-000V Primary AC current: 100A Secondary voltage: 1V

Can I remove the two burden resistors within the SCT-013-000V to make the sensor into an SCT-013-000? I.e. from VT to CT; what about the TVS, is the same TVS inside the CT and VT models?

You can remove the burden within the -100V, but you really need to have the TVS - because there won’t be one in the -100V while it has the internal burden (or if there is, there is no need for one – meaning I don’t wholly believe the YHDC data sheet).

If there is a TVS present, leave it there. If there isn’t, you need a bipolar TVS, or a pair of zener diodes, in series but facing opposite directions (i.e. A-A or K-K). Almost any voltage will do, 5.6 V upwards to say 12 V - the sole purpose is to give the c.t. a load to hold the voltage down if it’s disconnected from the external burden, the one inside the emonTx, emonPi or on your breadboard.

It won’t exactly be a SCT-013-000, because I think the ‘voltage’ versions have a slightly different number of secondary turns (1860 vs 2000 nominally), you’ll need to adjust the calibration to take account of that. I think the ratio will be 100 A : 53.76 mA

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if you can measure the internal burden after you’ve got it out, I’d be interested to know what the value is.

I presume you’ve figured out how to take the c.t. apart – there are two plastic ‘spring clips’ that hang over the edge of the bobbin, push those aside (this needs 4 hands) and the core and bobbin will slide out.

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Many thanks Robert, I’ve taken it apart, will measure and update this thread.

On opening the VT I see 2x resistors plus a diode (?); I want to remove the resistors, I’m not sure on that third - leave in, remove, or replace?

Well, now there’s TWO surprises. :open_mouth:

First, the large component marked “WP” is the TVS, which I don’t think is needed when you have burden resistors, but they seem to think so (or maybe it’s too much trouble to leave it off). You need to keep that, but remove the two resistors (the 22 Ω [labelled 22R0] and the 220 Ω [labelled 2200]).

The second surprise is the value of those resistors. In parallel, they make exactly 20 Ω, which means the c.t. winding is 50 mA, so it’s exactly the same secondary as the SCT-013-000 without the ‘V’.
Those resistors need to go - a soldering iron with a bit big enough to cover both ends of the resistor at the same time works very well, melt the solder and wipe the resistor off with the iron.

Do be careful and whatever else you do, don’t break the secondary winding wire. It is very delicate.

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