In anticipation of these demands, transducer specialist LEM has created a measurement technology that allows for unprecedented levels of accuracy in onboard monitoring of energy consumption in trains.
These adapted and optimized devices consist of current and voltage transducers, as well as a new energy meter. All three units offer unprecedented levels of accuracy in the industry and are supplied with industry-recognized certification for electric rail traction. When used together, they enable designers to meet or exceed existing or future specifications. They also offer the same levels of accuracy to system designers working in other high-power electrical supply segments.
In the high-precision power transducer, current is monitored using new additions to LEM's ITC 4000 or ITC 2000/1000 ranges. The ITC 4000, certified for Class 0.5R, employs an advanced closed-loop (compensated) current measurement design based on the magnetic induction (Fluxgate) principle. Rated at 4000 A, the ITC 4000 will measure +/-6000 A with a current draw of less than 80 mA (with zero primary current) and even below +/-340 mA (for a 4000 A primary current) from a +/-24 V power supply to its measurement (secondary) circuit.
Magnetic induction (Fluxgate) technology is distinguished by its high levels of accuracy and linearity; the linearity error of the ITC 4000 is below 0.05%. The device's offset current is less than +/- 10 mA and it also offers extremely low temperature drift. The ITC 4000 operates between -40 and +85 °C and meets or exceeds all relevant safety and performance standards.
For voltage measurement with the same standards or accuracy, LEM offers a new development of its DV series voltage transducer, covering voltages from 1200-4200V RMS. Initially introduced with Class 1 accuracy, the new development has brought the DV series to Class 0.75 accuracy. The DV series offers (as an active device) a current consumption of 19-23 mA, a measurement frequency bandwidth of 12 kHz, and an insulation voltage of 18.5 kV.
The DV series devices are more compact than any competing transducer, measuring only 134 x 54.22 x 147.25 mm. Like its counterpart for current measurement, it meets all the requirements of the railway industry regarding EMC performance, partial discharge voltage, and safety; it is also characterized by its low weight, flexible mechanical mounting, and electrical output characteristics.
Completing this technological measurement package is LEM's EM4T II single-phase energy meter, also with Class 0.5R accuracy. This accuracy specification conforms to the proposed EN 50463 standard, which will unify measurement practices for cross-border rail movement in Europe. The EM4T II is a four-channel device that records data such as load profile, train data, and location (via GPS) at regular intervals. When used in conjunction with the ITC 4000 current transducer, the EM4T II accurately records bidirectional power flow, enabling precise energy usage monitoring even during regenerative braking.
