UNIPOWER modules at the heart of “silent” power shelf from Communications Audit

Not so Communications Audit UK Ltd, widely known as CommsAudit specialises in supplying the surveillance and electronic warfare (EW) communities with turnkey receiver and monitoring systems operating up to UHF levels. CommsAudit’s manufacturing facility provides a clue as to the type of high end-customer the company supports with its industry-leading RF solutions and systems designed to meet a broad spectrum of specialist national security, defence and telecoms applications.

“Many of our systems find themselves at the heart of an aerial farm or as the basis of a communications system pulling in extremely low level signals”. Explains CommsAudit’s Technical Development Manager, Ian Thomson OBE. “As a result, the last thing we or the customer needs is a raised background noise level and the biggest culprit in any modern electronics-based system is usually a switched mode power supply.

“When designing the power shelf currently used in many of our rack mount systems, the obvious choice was to use linear technology at the rectifier stage.” Says Ian Thomson. “Linear power supplies are inherently very quiet, are less complex than switch mode units, but are larger, heavier and generate more heat. These mechanical and environmental factors would not normally influence the choice of unit for a rack mounted system, but we needed to provide the security of redundancy so, on size alone, our designers were forced to consider switch mode rectifiers.”

Switch mode power supplies are more complicated than linear models and their switching currents can cause electrical noise problems if not carefully suppressed, and simple designs may have poor power factor performance.

There were a number of power supply manufacturers capable of meeting CommsAudit’s initial requirements of power output and size, but the field narrowed when redundancy, hot swap capability and Built in Test (BITE) were added to the specification. Utilising features of the Unipower design, CommsAudit have been able to provide full remote monitoring and control via IEEE 802.3 Ethernet connection.

The power modules selected by CommsAudit were UNIPOWER’s Ranger Series of hot-swappable power supplies which are available in several power output versions capable of providing up to 100A for the 12V model. Ranger modules provide output voltages from 12 to 54.4V. With a height of just 3.5in or 2U and a power density of up to 11W/in³, three Ranger modules can be accommodated in a 19in rack mount system with active load sharing and integral ORing diodes. With a power factor reading of 0.99, Ranger units meet all applicable EMI and ESD standards including Bellcore GR-1089-Core and EN61000-4-2. Each module weighs just 4.6kg (10.15lbs).

Although UNIPOWER’s Ranger modules are fairly “silent”, CommsAudit’s power shelf filters out any remaining conducted and emitted noise resulting in a silent power source that provides the basis of its monitoring and receiving systems. CommsAudit’s power shelves have passed rigorous Emissions Standards: EN 61204:3, EN55022, EN55024, EN61000-3-2, EN61000-3-3 and the EN60950-1 safety standard

According to UNIPOWER’s European Sales and Marketing Director Nigel Frey, CommsAudit’s choice of the Ranger modules recognises UNIPOWER’s industry leadership in high density, hot swap power sources for high performance applications.

“UNIPOWER has been producing high power rectifier modules for many years continually increasing the power density and efficiency levels to meet the demands of the communications and datacoms industries.” Says Nigel Frey.
“Our latest units offer power densities as high as 24W/in³ and efficiency levels up to 92% which, when combined with their hot swap capability and auto load sharing, make them ideal for today’s power hungry applications.