23 Jul 2024


Tiny current sensors could lead to smaller, more efficient VSDs

Japanese developers have produced a tiny, precision current sensor that, they predict, could lead to lighter, smaller, more efficient inverters. The GCBC sensor uses a proprietary magnetic sensing element that eliminates the need for a core to concentrate magnetic flux, resulting in a board-mounting device that weighs just 3g.

Current sensors usually adopt one of two approaches – measurements based on shunt resistance, or measurement of the magnetic flux generated around a current conductor. The DC current transformer (DCCT) approach, using flux measurement, offers precision at a low cost. It is usually used with low-sensitivity magnetic elements and therefore needs a magnetic core to concentrate flux around the conductor. This can result in large, heavy components.

In addition, conventional current sensors can become hot quickly because of high resistance in the primary conductor, leading to power losses.

The new PCB-mounting current sensor is claimed to be the smallest and lightest available. The device uses a proprietary high-sensitivity magnetic sensor element, based on the GMR (giant magneto-resistive) principle, that eliminates the need for a core to concentrate magnetic flux. The result is a device that measures 13.4 × 15.7 × 7.2mm and weighs just 3g.

Proprietary magnetic control plates positioned around the sensor element ensure high sensitivity and resist external interference.

Resistance in the primary conductor is claimed to be the industry’s lowest at 60µΩ. This is 40% lower than rival current sensors and reduces heat generation, helping to cut power losses, according to the sensor’s developer, Alps Green Devices, which is an alliance between the Japanese component manufacturer Alps Electric and the Innovation Network Corporation of Japan. The alliance develops and manufactures compact, efficient power conversion and control devices for low-carbon applications.

The sensors can measure maximum continuous currents up to ±50A and there are plans to extend their capacity up to 150A.

Alps Green Devices expects the sensors to be used in applications such as variable-speed drives, general-purpose inverters, power conditioners, NC machine tools and air-conditioning systems. Mass production is due to start in October this year and Alps expects to be producing about 100,000 sensors per month by April 2015.