Coreless current sensor enables smaller, cheaper, lightweight xEV inverters

Coreless current sensor enables smaller, cheaper, lightweight xEV inverters

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The AC37612 is a coreless Hall-effect current sensor – the industry’s first, says its vendor Allegro MicroSystems. The device measures currents from 200A to >1000A flowing through a PCB or a busbar with a typical accuracy of 1% — and without requiring a magnetic concentrator core or a shield.
By Christoph Hammerschmidt

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The differential Hall-elements used in the AC37612 to measure the magnetic field provide high immunity to stray magnetic fields without the need of a laminated shield required by competing solutions, which reduces the design size and bill of materials (BOM). With these properties, the product is ideal for demanding electric vehicle applications, such as high-voltage traction inverter phase current measurement, 48V starter generators and battery disconnect. This refers to battery-electric vehicles and hybrids of all kinds alike. “It is the first solution that provides a truly coreless method of accurately measuring hundreds of amps in a very small formfactor, solving a key challenge for automotive engineers,” says Georges El Bacha, Product Line Manager at Allegro.

During acceleration, hundreds of amps flow through the traction motor inverter of an electric vehicle. A precise measurement of such high currents is vital for safe performance. Engineers have traditionally relied on a low hysteresis, laminated core for such measurements — using three to six cores, depending on the number of phases in the motor.


Eliminating these cores with the ACS37612 allows manufactures to reduce the space and weight of the inverters, thus increasing the efficiency of the electric vehicle. This non-invasive, contactless current sensor is designed to improve thermal efficiency relative to shunt solutions and is therefore ideal for reducing system energy consumption in 48V e-motor platforms.

The ability of the ACS37612 to be used in either busbar or PCB designs provides engineers with mechanical flexibility and simplifies their system level solution. The system coupling factor is determined by the sensitivity level of the ACS37612, as well as the shape and location of the busbar, making it easy to increase the current sensing range at any phase of the design.

The sensor is available in a very small TSSOP8 package (LU-8) that has a 3mm x 6.4mm total PCB footprint. Together with the coreless design, the ACS37612 enables a very small and light current sensing solution.  

More information: allegromicro.com.

 

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