Current sensor for EV traction inverters delivers smallest footprint

LEM has introduced a current sensor that it claims is the smallest of its kind on the market.

With distance and speed of charging vital in the competitive EV sector high-power integrated traction inverters – which convert DC into AC and capture energy for the vehicle – need to combine performance with being as small and light as possible.

Measuring 29mm x 21mm x 12mm and weighing 27g, LEM’s new HSTDR current sensor is significantly more compact than a traditional C-core sensor, making it much easier to be integrated into space-limited inverter boxes.

The sensor enables traction inverters to operate at maximum efficiency by combining high accuracy with affordability and the ability to operate in demanding environments (the sensor has an operating range of -40°C to +125°C and is robust enough to cope with vibrations up to 10G).

Using open loop Hall effect technology and a magnetic core design, the HSTDR offers immunity against external field and cross talk as well as consistent behaviour over frequency with little part-to-part phase shift dispersion, ensuring more accurate torque control.

The sensor is not only 42% smaller than its predecessor (LEM’s HSNDR) but also weighs 50% less and offers 50% greater measuring range, as well as best-in-class accuracy and a global error over temperature and lifetime below 3.5%.

Giving EV manufacturers the choice of having different current measuring ranges in the same housing – from ±300 A up to ±1500 A – the sensor ensures galvanic separation between the primary circuit (high power) and the secondary circuit (electronic circuit), which is also suitable for 800V battery systems.

The HSTDR is also the only sensor for EV traction inverters, DC link and 3-phase current measurement to feature an integrated busbar, starting with the earlier HSNDR, fitting perfectly into the smallest possible core aperture.