Transducers reduce bulk

Designed for insulated nominal voltage measurements in traction applications, the DVM series of transducers spans 600 to 4,200VRMS and incorporates LEM’s patented insulating technology. The transducers achieve high levels of isolation with a safety insulation voltage of 12kV, yet are housed in a compact housing that measures 138 x 63.4 x 69mm.

The series is suitable for base mounting, but with slightly different outline dimensions to earlier versions, to take into consideration primary and secondary connections locations, for example. It is also 30 per cent small in height, occupies 25 per cent less volume and is 56 per cent lighter than earlier versions. Despite their size, the transducers offer high immunity against the external surrounding perturbations or against the high voltage variations. The size is also an advantage for size constraints in modern railway propulsion converters, says the company.

The series is compliant with the International Railway Industry Standards (IRIS), and is equally applicable to measuring network voltages, or the main converter DC link on-board trains. The feature set also makes the transducers suitable for medium to high voltage measurements in industrial markets.

The transducers measure voltages by a direct connection on their primary side, transfer the data across an internal isolation barrier and output a current from their secondary side; that is proportional to the measured voltage thanks to the patented insulating digital technology used. Typical accuracy is ± 0.5 per cent at +25°C with a higher stability in temperature. The technology provides high levels of immunity to external magnetic fields (almost insensitive) and electromagnetic disturbances (unmatched level). Combined with a highly focused internal electronic design applied on the printed circuit as well as for mechanical design performance reached in common mode condition are 0.5 per cent nominal voltage as error generated with a recovery time of less than 50micro seconds against a voltage of 4,200V applied with a step of 6kV/micro seconds.

Measurement frequency bandwidth (-3dB point) is 12kHz and typically just 30mA is consumed at ±24V DC (range is from °±13.5 to ± 26.4V DC). Two kinds of current output ranges are possible either ±50mA, or the standard industrial current-loop range of 4 to 20mA for uni-polar current measurements and one voltage output at 10V for nominal voltage.

Other key features include a high level of partial discharge extinction voltage (5kVRMS at 10pC) and compliance to a range of internationally-recognised safety standards in addition to its adherence to IRIS specifications. The series is CE marked and is supplied with a five-year warranty.

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