The high precision Current Comparators (current transformers) are used to convert high currents to a lower, measurable level. The errors of conventional standard current transformers inevitably depend on their burden. A magnetic flux in the core produces the e.m.f. which sustains the secondary current in the burden. This disadvantage has been eliminated by the
development of the new current comparators. An indicator winding measures the magnetic flux in the core, while an amplifier – by regulating the current in a compensating winding – ensures that the amplitude of the residual flux in the core is approximately zero.
With this technique, the high precision Current Comparators will maintain typical current ratio errors below 20 ppm and current phase errors below 0.15 min on a long term basis over an extremely broad current range. This electronically controlled current transformer is specifically designed for current range extension in capacitance measurements. It has divider measurements of 1:10 and 1:100. The special transformer is accommodated inside a portable casing with all terminals on the top panel.

Advantages

• • • Negligible transformer error eliminates calculation of measured C and tan d correction factors
    • Accuracy at best level – The 4762 units are prepared for accuracy testing of current instrument transformers with most stringent accuracy requirements – 476x units are qualified for use as standard current transformers in metrology institutes.

Applications

• • Accuracy test on current instrument transformers
  • Range extension of capacitance and tan d bridges