Transducer sets new accuracy benchmark in traction current measurements

LEM has announced the ITC series of transducers for galvanically-isolated, high-precision current measurements in rail-traction applications, setting new standards in measurement accuracy for DC, AC and Pulsed currents.
LEM’s new transducer series comprises three models, ITC 1000-S, 2000-S and 4000-S, with corresponding nominal current measurement ratings of 1000, 2000 and 4000 ARMS. LEM designed the ITC series for the rail-traction industry sector, reaching the Class 0.5R measurement accuracy when Class 1R is required by the prEN 50463 standard for on-board energy monitoring. The ITC series features linearity error of under 0.05% with offset currents of less than +/- 20µA.

Picture: LEM

The rail-traction industry requires unprecedented accuracy necessary of course to maintain optimum control of traction motors, but mainly in energy metering to log energy usage for fiscal purposes, for example in billing power costs for trains that cross regional borders. The industry is working to a provisional (“pr”) standard designated prEN 50463.
Precise energy metering depends on accurate current and voltage measurements, and LEM has a complete offering for prEN 50463. Used together with highly-accurate voltage transducers such as the LEM DV series (available in Class 1R or Class 0.75R certified accuracy), and an energy meter such as LEM’s EM4T, ITC-series current transducers bring the necessary class accuracy.
LEM’s measurement specialists determined that Hall-Effect-based measurement techniques could not provide the required accuracy, and instead used its expertise with the closed-loop fluxgate, resulting in a design with excellent accuracy and linearity, low thermal drifts and which also eliminates insertion losses. ITC transducers are insensitive to the position of the primary conductor within their large measurement aperture, offer high insulation test voltage of up to 14 kVRMS/50 Hz/1 min, and have excellent immunity to transient overloads (100kA for 100msec) and to external interferences (such as magnetic fields typical of the rail environment).
Current consumption varies from less than 80 mA to under +/-340 mA across the measurement range, from a +/- 24VDC supply. Bandwidth for the ITC 4000-S is 82 kHz (3 dB) and the transducers’ apertures allow the insertion of large conductors: 102 mm diameter (for the ITC 4000-S) or 63 mm diameter (for the ITC 2000-S). A test winding allows the operation of the ITC transducers to be easily checked with no primary current flowing.
LEM offers the ITC series in either a one-piece housing (ITC 4000-S model), or a split construction (ITC 1000 and 2000-S models) with the measurement head in a case, and the measurement circuitry mounted remotely in a metal enclosure, to facilitate locating the measurement head in confined spaces such as the train roof space.
ITC transducers operate over the range –40 to +85°C, and meet or exceed all relevant standards for safety and for the railway operating environment, such as EN 50124-1 and EN 50155.
Their high accuracy also makes the ITC transducers ideal for use in a broad array of differential current-measurement applications where 0.5% accuracy, over 5 to 150% of nominal current, is required.

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