Hi all, I have some question about this 100A current transformer without burden resistor, what is this smd component? A zener diode?This is new version of CT?
I ask this because in the other versions of 100A we can find inside it two zener, so why I have only one component on the circuit? The connection traces are very strange, i can draw a circuit if necessary.
Thanks for your support. Regards
Your picture is not sharp, so I cannot read the number on the device. But I have no doubt that it is a voltage-limiting component, and should not affect operation in any way. The specification has not changed.
I believe the same circuit board is used for the whole range of CTs, and the versatility is there to allow a choice of either voltage limiter or burden resistors (possibly more than one, in series/parallel as required) etc to be made at final assembly and test, in order to meet the product specification.
[quote=āRobert.Wall, post:2, topic:617, full:trueā]
Your picture is not sharp, so I cannot read the number on the device[/quote]
I think it is your eyes 
image is very sharp here.
Code on the component is
WP
Then underneath a 0 rotated about 45 degrees, with something similar to a tilde through it (almost an s rotated -45)
Really?
Quite a bit sharper than yours it seemsā¦ what are you viewing on? I am in MS edge
The code is āWPā guys. I think it is a zener diode, but the problem is: why i have only one zener?
Itās a special component with two zener in series inside it?
That is what I would expect - it is clearly cheaper to have one component than 2. But I cannot identify the makerās mark, and āWPā isnāt exactly unique. What I would expect is it is something like this.
Itās possible, but I donāt think it is that one, not with a 80 V breakdown voltage, which is unreasonably high. I would expect something in the 5 - 20 V range. The original wire-ended zener diodes were 22 V, therefore clipping at about 22 - 23 V, and later replaced by 2 SMT diodes at (I think) 7.5 V and thus clipping at around 8 V.
The way to find out is to repeat the test I did on the original CT - itās in Resources > Building Blocks.
For what itās worth, the logo looks like General Semiconductor (taken over by Vishay several years ago). According to a helpful marketing lady at Beijing Yaohuadechang Electronic Co., Ltd (the YHDC SCT manufacturer) āYes we changed the component more than 1 years ago, but they are the same function, do not worryā
So there you have it - donāt worryā¦ 
Getting part numbers from most Chinese vendors is for various reasons like pulling teeth - measure it if you are really interested (back to back zeners)
Glyn is sending me one of the new CTs, so Iāll be able to test it and report, when Royal Mail have done their stuff.
Royal Mail has performed on-time, and I can report that clipping takes place at approx 8.5 V (17 V p-p) 9.2 V (18.4 V p-p) and starts at approx 4 A primary current, of course with no burden.
And having looked at the construction, YHDC are improving the build quality of this CT all the time. Particularly impressive is the way the bobbin moulding has been extended to support the PCB, which very much reduces the possibility of snapping the secondary winding wire if the assembly is mis-handled.
Even knowing the voltage, I still havenāt succeeded in identifying the part. Maybe what appears to be the GE logo rotated 45Ā° is a Chinese manufacturer that isnāt listed in the usual sources?
Thanks for testing Robert.
I have head back from YHDC
The value of the diode voltage limiter component is 7.5v and specification of the voltage limiter component is SMAJ7.5CA
Datasheet: http://www.farnell.com/datasheets/1865118.pdf
Farnell: http://uk.farnell.com/multicomp/smaj7-5ca/diode-tvs-7-5v-400w/dp/1579020
See attached for factory test report:
SCT013ļ¼100Aļ¼50mAļ¼Test report.pdf (263.0 KB)
