TH2883 Series Operation Manual Chapter 2 General specifications
2-4
Then, a new effective value can be set by adding 20% to the maximum corona discharge value.
In order to ensure the correctness of the new value, user can test these coils once more and
observe the corona PASS or FAIL.
2.2.4 Differential phase comparison
User can specify a zero-crossing point to compare. The instrument will judge the zero-crossing
offset between the tested waveform and standard waveform and then compare the oscillation
period between the two waveforms. The percentage of the two values will be taken as the
judging criterion and the reference is set by percentage. As is shown in figure 2-4, A~B is the
offset and C~D is the oscillation period of standard waveform. The third zero-crossing point of
the compared waveform is to set.
Figure 2-4 Phase Differential Comparison
NOTE:
The tester can only set zero-crossing points from 2 to 10. The first zero-crossing point
cannot reflect the actual performance of coils, so it is not necessary to set the first point. In real
phase differential comparison, there are four results generated: PASS, FAIL, FAIL1 and FAIL2.
PASS is up to standard; FAIL, below standard. While FAIL1 means the zero-crossing point has
not been found, that is to say, it is unable to find the set zero-crossing point on the waveform of
the tested coil; FAIL2 indicates that a complete period cannot be found on the standard
waveform. As shown in figure2-4, the third zero-crossing point must be present in the waveform
so as to ensure the normal operation of phase differential comparison.
