Medium and high voltage transducers for traction drive control

September 21, 2016 // By Graham Prophet
Swiss transducer specialist LEM’s DVM series makes insulated nominal voltage measurements in traction applications. This family of devices spans 600-4200 VRMS and incorporates LEM’s insulating technology. Despite achieving very high levels of isolation with a safety insulation voltage of 12 kV, the DVM transducer measures 138 x 63.4 x 69 mm.

It is fully compatible and out-performs the previous generation of transducers in terms of functions and performance with new improved levels of accuracy and temperature stability, simplifying retrofits. DVM is also suitable for base mounting, but with slightly different outline dimensions. The DVM is 30% smaller in height, occupies 25% less volume and is 56% lighter that its predecessors. The reduction in size does not compromise the DVM’s high immunity against the external surrounding perturbations or against the high voltage variations. The new size is also an advantage when confronted with size constraints in modern railway propulsion converters.


LEM developed the DVM to be fully compliant with the International Railway Industry Standards (IRIS) while the feature set of the DVM voltage transducer also suits it for a broad range of medium to high voltage measurements in industrial markets.


DVM 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, proroportional to the measured voltage. It delivers an improved typical accuracy, compared to existing products, of ±0.5 % at +25°C with a higher stability in temperature. The technology used provides very high levels of immunity to external magnetic fields (almost insensitive) and electromagnetic disturbances. In common mode, parameters are; 0.5% of nominal voltage as error generated with a recovery time of less than 50 µsec against a voltage of 4200 V applied with a step of 6 kV/ µsec.


Its measurement frequency bandwidth (-3 dB point) is 12 kHz and the DVM consumes typically 30 mA from ±24 VDC (power supply range from ±13.5 to ±26.4 VDC). Current output ranges are either ±50 mA, or the standard industrial current-loop range of 4 to 20 mA for unipolar current measurements and one voltage output at 10V for nominal voltage.