Inductive sensor provides a compact, lightweight solution for EV motor position measurement

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Developers of motor control systems are moving toward replacing Hall effect position sensors and older magnetic resolver solutions with inductive alternatives that eliminate expensive magnets and other heavy transformer-based structures so they can be integrated onto simple, compact printed circuit boards (PCBs).

Extending its line of inductive position sensors into the EV motor control market, Microchip Technology has released the LX34070 IC, which has been purpose-built for EV motor control applications. It includes differential outputs, fast sample rates and features that make it functional-safety-ready for ISO 26262 compliance in the Automotive Safety Integrity Level–C (ASIL–C) classification.

“The LX34070 inductive position sensor enables lighter, smaller, more reliable motor control solutions that meet stringent safety requirements, reduce overall system costs and can operate seamlessly and precisely in the noisy environment of an automobile’s DC motors, high currents and solenoids,” said Fanie Duvenhage, vice president of Microchip’s mixed-signal and linear analog business unit. “Designers can use the LX34070 to further streamline EV motor control designs by pairing it with other functional-safety-ready Microchip devices including our 8-bit AVR and PIC microcontrollers, our 32-bit microcontrollers and our dsPIC digital signal controllers.”

The company states that the LX34070 inductive position sensor solution offers numerous advantages compared with magnetic resolvers and linear voltage differential transducers (LVDTs), at a fraction of the cost. By using PCB traces rather than transformer-based magnetic windings and coil structures, the LX34070 device has negligible size and mass compared with alternatives that weigh as much as 450g. Accuracy is improved since the LX34070 does not depend on magnet strength, and the device improves robustness by actively rejecting stray magnetic fields. These and other features give designers greater flexibility over where they can place the thin, lightweight PCB-based LX34070 solution in their EV motor control designs.

PCB-based inductive position sensors use a primary coil to generate an AC magnetic field that couples with two secondary coils. A small metal target object disturbs the magnetic field so that each secondary coil receives a different voltage, the ratio of which is used to calculate absolute position. Using these techniques, Microchip introduced its first high-volume inductive sensor for automotive and industrial applications over a decade ago and has many programs in volume production.

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Lawrence has been covering engineering subjects – with a focus on motorsport technology – since 2007 and has edited and contributed to a variety of international titles. Currently he is responsible for content across UKI Media & Events' portfolio of websites while also writing for the company's print titles.

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