Tonghui TH2829 Series - Unstable TURN; Difference between the First and the Second Lx; Poor Stability of CX and Zx Open Test Data; DCR and PS Open Cannot Reach Infinite Large

TH2829X Series Operation Manual Chapter 7 Transformer Auto Scanning Test
137
7.16.7 Unstable TURN
For the transformer with high magnetic permeability magnetic-core，test winding
will be unstable.
Solution:
1. Use the TURN-v mode to test winding (voltage-turn mode).
2. Use deviation deduction.
7.16.8 Difference between the first and the second Lx
Because the transformer, with high magnetic permeability magnetic-core, is
polarized in the test of DCR or TURN, the test results of the first and the second
Lx test will be quite different.
Solution:
Use the 100Ω internal resistance in the test of TURN or DCR.
7.16.9 Poor stability of Cx and Zx open test data
If the shielding and ground of test system is not good, it will cause the test value
unstable when testing Cx or Zx.
Solution:
Through a thick metal lead, connect ground poles of the instrument and the scan
box as well as the metal frame of the test fixture together and ground it reliably.
7.16.10 DCR and PS open cannot reach infinite large
Due to the existence of circuit distribution parameter, so the infinite large cannot
be displayed when testing DCR or PS open, it is an normal phenomenon, if user
wants to display it, execute the sweep open correction function on the test
fixture.
7.17 User-made test fixture
There are many kinds of transformers, so our company can’t offer a test fixture to
each transformer, which requires user to make a test fixture according to some
principles. The followings are caution items of making test fixture
：
1. Use 4-cable measurement method to extend test cable. Don’t use 5.0mm
test fixture to hold test lead.
2. Use multi-strand lacquer cable with good tenacity to be the test extension
cable. And use the stands as much as possible to reduce the resistance of
cable.
3. Use high frequency test, and reduce the distribution parameter within