LEM 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.

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.

ITC models are CE marked and, in common with all LEM industrial transducers, carry a five-year
warranty.

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