Power Electronics Europe Issue 4 - November 2022

www.lem.com AUTOMOTIVE CURRENT SENSORS 25 www.power-mag.com Issue 4 2022 Power Electronics Europe placed anywhere in the traction inverter. Of course, a smaller magnetic core also means that the overall weight of the sensor can be reduced by around 50 %. As a consequence, the sensor can handle vibrations of up to 10 g, which is now a standard requirement in automotive environments. Another benefit of a smaller magnetic core is that it reduces the amount of raw materials required in the sensor build, keeping costs down. Also, there are considerable time-saving and productivity advantages associated with having a fully calibrated sensor that incorporates core, busbar and sensing element in a single package (see Figure 3 and 4). Key design considerations for the new sensor When LEM’s engineers designed the HSTDR single-phase current sensor with the EV traction inverter market firmly in mind, they had three key considerations. Firstly, the restriction mentioned earlier on the integrated busbar should be large enough to ensure mechanical stability while preventing additional power loss and heat dissipation in an already extremely hot environment. As a result, resistance introduced by the restriction on the busbar is negligible at no more than 20 µ Ω (see Figure 5). Secondly, with the magnetic core directly mounted on the busbar, it was important to design an isolation barrier between the electronic and the magnetic core, to ensure enough clearance and creepage distance for 800V battery systems. Finally, it was important that – because the sensor would be operating in harsh and noisy environments – its output would remain immune to high switching speeds (dV/dt) – see Figure 6. One other point of note is that, in terms of accuracy, the HSTDR current sensor delivers a global error over temperature and lifetime of less than 3.5 % over a dynamic range up to 1500 A. Also, because the unit offers consistent performance over a range of frequency levels with minimal part-to-part phase shift dispersion, it is capable of ensuring accurate torque control which is an essential factor in EV motor drive applications. Conclusions Having produced its first current sensor for battery monitoring systems over 20 years ago, LEM is no newcomer to the automotive market and the company is continually developing innovative new products for this demanding sector. LEM has built up an extensive portfolio of such products as sensors for use in traction inverters, DC/DC converters and on-board chargers, with the aim always to go smaller and smarter wherever possible. The company focuses on solving customers’ problems by exploring today’s technologies to take them further as well as developing tomorrow’s solutions by foreseeing future challenges and working to address them. Figure 4: HSTDR 1500 A single-phase current sensor including restrictions LEFT Figure 5: HSTDR busbar restrictions RIGHT Figure 6: HSTDR immunity to high switching speeds (dV/dt)