Bosch- and Siemens-branded washing machine technology leads to clothespin energy analyzer
By Anthony Capkun
May 15, 2012 – Until recently, large-scale industrial energy users in Germany have benefited from reduced tax rates on the electricity and gas they consume. Now the German government has decided that companies will only be eligible for such tax breaks when they take steps to reduce their energy consumption. From 2013 onward, tax rebates will only be granted to companies equipped with an energy management system that provides details of their power consumption.
This won’t be an easy task for the companies concerned, because it means they will have to install individual auxiliary meters to monitor the power consumption of individual loads such as presses and welding machines, bakers’ ovens or electric motors. In some cases, the metering instruments currently available on the market are too large to fit into existing power distribution cabinets.
To remedy this situation, researchers at the Fraunhofer Institute for Integrated Circuits IIS in Erlangen have developed a space-saving metering unit that can be simply clipped onto a power cable like a clothespin without having to disconnect the load. The ‘energy analyzer’ was developed in collaboration with Rauschert GmbH, a manufacturer of ceramic products that require energy-intensive production processes.
The device is based on the HallinOne 3-D magnetic field sensor originally developed by IIS for use in Bosch- and Siemens-branded washing machines, where it monitors the position and orientation of the rotating drum.
“This new device is the first application in which we have used our 3-D magnetic field sensor technology to measure the magnetic field generated by an electric current as a means of determining the energy consumed by the connected load. As such, it is an entirely novel approach,” said IIS research scientist Michael Hackner.
To build the device, he and his team of engineers mounted eight sensors in the form of application-specific integrated circuits (ASICs) on a flexible, flat circuit board. What sets these sensors apart from more conventional designs is they measure the magnetic field—not only perpendicular to the surface of the chip but also in tangential directions, which improves measurement accuracy. The recorded data is transmitted to a microcontroller, which forwards them to a central processor via a gateway switch.
“Our power sensor is quick to install and can be integrated online,” said Hackner, citing one of the advantages of the new product. He goes on to emphasize another unique design feature: the fact that it functions in the same way as a Rogowski coil. “But the Rogowski coil only measures alternating current, whereas the IIS sensor can also measure direct current—an important consideration when measuring the power consumption of photovoltaic systems that include solar inverters for converting DC output into AC power.”