Power Management
Meeting the monitoring challenge
Robert Racz & Mathieu Ackermann look at the growing adoption and use of Hall Effect sensing technology in managing and monitoring current consumption in modern PDU systems
P
ower distribution units (PDUs) play a key role in today’s computing and networking sectors. These multiple output items of rack-mounted electronic hardware allow the efficient transfer of power throughout datacenters and other communication hubs. The market for PDUs is growing rapidly fuelled by the need for ever greater levels of computing power, larger data storage capacities and higher levels of bandwidth. Industry analyst firm TechNavio predicts that the global PDU market for datacenters will be worth in the region of $770 million annually by 2014, as existing equipment is upgraded in order to make it more energy efficient and enhance system reliability. With a significant proportion of modern power infrastructure now being provided
through PDUs, the degrees of reliability and efficiency that they are able to offer is critical. Stringent legislation that has been put in place to curb carbon emissions means a great deal of pressure is being directed onto datacenter engineering staff. The ability to accurately monitor and carry out in-depth analysis of on-going power consumption is now therefore of great importance to PDU manufacturers, so that the equipment they produce can keep pace with the power unit effectiveness benchmarks being set by companies such as Google and Yahoo. There are various methodologies being employed for the sensing of the current consumption for each input/output in a PDU system. Many of these have serious technical challenges associated with them however.
Current sensing challenges Sensing systems being utilized for monitoring PDU current consumption need to be able to deal with high voltage transients. Likewise these systems can potentially be left vulnerable to inrush currents. As a result, a high degree of protection needs to be factored into the sensor system’s design. As space within a datacenter environment is at a premium, a small footprint is also desirable. Furthermore system accuracy needs to be maximised.
Hall Effect sensing From basic electromagnetic theory it is well known that the flow of an electrical current through a conductor generates a
magnetic field around it. The field generated can be detected through the principles of the Hall Effect. The sensor output voltage is proportional to the current. Use of Hall Effect sensors offers a non-contact technique for monitoring of PDU electricity consumption which improves system longevity. Conventional Hall Effect sensor solution
implementations will unfortunately take up a considerable amount of board space and are relatively expensive too. The main problem witnessed with these sensing devices is that they only respond to magnetic fields that are perpendicular to the sensor surface. As these sensors rely on use of a looped ferrite core they will not only be bulky and expensive, but
Figure 1: PDU Schematic 22 October 2012 Components in Electronics
Figure 2: Conventional Hall Sensor
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