During the switching process of on-load tap-changers, abnormal measurement data for transition resistance and transition time is a common feedback encountered by procurement personnel during model selection. On-site issues reported are concentrated in two aspects: first, the instrument's nominal transition resistance measurement range does not match the actual switch resistance values, resulting in some tap positions being unable to be collected; second, the transition time measurement accuracy is insufficient to truly reflect the timing changes of contact switching.
Regarding the resistance coverage issue, procurement personnel should first verify the instrument's transition resistance measurement range at the 1A range. Taking a starting range of 0.4Ω as an example, it can cover switch types with low-resistance transition resistors, avoiding the inability to measure low-resistance tap positions due to an insufficient lower limit of the range. At the same time, it is necessary to confirm whether the instrument supports multiple current outputs, so as to obtain stable measurement signals in different resistance ranges.
For transition time measurement, attention should be paid to the instrument's sampling rate and signal processing method. 10kHz high-speed sampling combined with six independent signal processing channels can capture the timing details of contact action with sufficient time resolution, avoiding distortion of transition time readings caused by insufficient sampling rate. Procurement personnel can request to see the time resolution specifications of the instrument under typical switching waveforms, rather than only focusing on the nominal range.
After confirming the parameters, the instrument's capability to synchronously record transition resistance and transition time should also be verified, ensuring that both correspond on the same time axis, facilitating subsequent analysis of the consistency of the contact switching process. For test scenarios that require distinguishing multiple contact actions, six independent channels can record each contact signal separately, reducing the impact of crosstalk between channels on parameter interpretation.
During the selection stage, it is recommended to compare the nameplate resistance range of the on-site switch with the instrument's range tap by tap, and confirm whether the lower limit of transition time measurement meets the testing requirements of fast-switching switches. After parameter matching is completed, the convenience of daily use can then be evaluated in conjunction with the operation interface and data export methods.
