Small footprint current sensor for high-power EV traction inverters

Measuring only 29mm x 21mm x 12mm and weighing just 27g, LEM's new HSTDR current sensor is especially more compact than a conventional C-core sensor, making it much simpler to be integrated into space-limited inverter boxes.

The sensor allows traction inverters to function at maximum efficiency by integrating high accuracy with affordability and the ability to operate in tough environments (the sensor has an operating range of -40C to +125C and is robust enough to cope with vibrations up to 10G). The sensor uses open loop Hall effect technology and an innovative magnetic core design to provide excellent immunity against external field and cross talk and consistent behaviour over frequency with little part-to-part phase shift dispersion, ensuring more accurate torque control.

The sensor is unique because it is 42% smaller than its predecessor (the HSNDR), weighs 50% less, offers a 50% greater measuring range, and has best-in-class accuracy and a global error over temperature and lifetime below 3.5%. Supplying EV manufacturers the option of having different current measuring ranges in the same housing – from ±300A up to ±1500A – the sensor provides galvanic separation between the primary circuit (high power) and the secondary circuit (electronic circuit), which is also ideal for 800V battery systems.

The company's designers minimised the device's footprint by making it the only sensor for EV traction inverters, DC link and three-phase current measurement to offer an integrated busbar, starting with the earlier HSNDR, fitting perfectly into the smallest possible core aperture. Now, with access to a completely calibrated package of core, busbar and sensing element, car component designers and EV manufacturers will have the flexibility to gain major reductions in their products' time to market.

Says Sofiane Serbouh, LEM's global product manager, Motor Control: "Based on 50 years' experience in electrical measurement, LEM is continually pushing the boundaries when it comes to developing the solutions that design engineers in the automotive industry are looking for when working with traction inverters. The designers' challenge is to create EV car components that are not just high-performance but are also compact and light. The HSTDR fits the bill perfectly."