A/H1 N NHF/CAR 1n/X2 V 1a/X1 FSC C1 Lcomp C2 A/H1 N NHF/CAR 1n/X2 V 1a/X1 FSC C1 Lcomp C2 accuracy measurement from VOTANO 100, more in-depth diagnoses of the equipment can now be made, as the state of the capacitive stack can also be determined. Determining the C1 and C2 values is essential, as capacitance C1 is significantly smaller than C2. In other words, sometimes, a decline in the C1 capacitance state may remain undetectable with conventional measurement methods. The new measurement method allows any change to capacitances C1 and C2 to be detected by comparing the measured capacitance values with the values of earlier measurements or with the manufacturer data for these values, regardless of the CVT design. Therefore, these types of comparison measurements and the resulting trend curves represent another vital indicator for CVT conditions. The model for CVTs has been improved continuously. Research has been carried out, measurements performed, and some scientific work has also been published. The studies showed, for example, that the capacitive ratio could also be determined using frequency measurements. This also inspired us to think of other measurement methods for determining the individual capacitance values and led us focus on short-circuit impedance measurements. Short-circuit impedance can be calculated from the current and voltage if you short circuit the primary side and feed current into the secondary side. Therefore, we determined that it would be possible to create an equation system using two separate short-circuit impedance measurements, which could then be solved mathematically. In this measurement you can short circuit two points – the “Neutral High Frequency” terminal (NHF) and the high voltage. During the first measurement, NHF is grounded to determine the short-circuit impedance of C2 for different frequencies (Graphic 2). Then, a second measurement is performed in which the high-voltage part is also grounded so that C1 is parallel to C2 to determine the short-circuit impedance via the frequency (Graphic 3). The frequency measurement also provides a resonance frequency, which can be used to produce an equation system. «While the overall transfer ratio of a CVT can be determined when it comes to its capacitive voltage dividers; only the ratio of the two capacitances can be determined, not their values.» Graphic 2: Measurement setup for first short-circuit impedance. Graphic 3: Measurement setup for second short-circuit impedance 40
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