xiaozhang2267 - 2008-7-14 15:01:00
该仪器用于测量绝缘的介损时，可直接反映出变压器绕组对地的介损。此外，仪器还可用于测量变压器的励磁电流、变比等，在北美及世界许多国家中已广泛应用，Ｄｏｂｌｅ试验简直成了介损试验的代名词了。
期待关于现场使用经验的介绍。
Rick - 2008-7-14 21:41:00
M4000 Measurement Principles
The M4000 generates a 0-12 kV test signal with an internal sine wave generator, a 3 kVA power amplifier and a step-up isolation transformer. The M4000 then measures the voltage and current of the specimen and a reference impedance by periodically sampling instantaneous values with an A/D converter. The M4000 then calculates and reports test results by converting the sampled data into vector (magnitude and phase) quantities and applying
conventional ac circuit theory. All reported results – including power loss, power factor and capacitance – are derived from the vector voltage and current.
The M4000 rejects interference through the judicious application of shielding, line-synchronized reversal, and line frequency modulation (FM). The first two techniques are similar to those employed in the earlier Doble M2H product line. The FM technique involves running tests at sinusoidal frequencies 5% (or even 10%, if necessary) above and below the line frequency and averaging the
results. The choice is user configurable. The inevitable interference current component is removed from the sampled data set before test results are calculated using synchronous detection. This is a mathematical process that separates out a single frequency component in a given signal. It is analogous to a bandpass filter centered at the test frequency. Synchronous detection is also useful for removing harmonic distortion and random noise in the test signal itself.
As for the field test example, more to come!:) :)
xiaozhang2267 - 2008-7-15 10:07:00
感谢