LIGHTNING STRIKES AND SPIKES CONTAINED ON THE OUTSIDE

17th June 2009

The latest range of Metal Oxide Varistor (MOV) planar arrays from Syfer Technology are designed specifically to deliver comprehensive protection against lightning strikes and other transient events in military, aerospace and other safety critical applications. Incorporated into the connectors on the external wall of the subsystem, the devices are key to protecting the increasing volume of sensitive electronic circuitry found in today’s complex systems. “Potentially damaging voltage spikes need to be suppressed or grounded sooner rather than later,” highlighted Chris Noade, Marketing Manager with Syfer Technology. “Relying on PCB-based transient voltage protection means that the spike is already inside the box.

Filtered connectors provide the ideal means of stopping the spike on the outside,” he explained. With multiple, interconnected ‘black boxes’ it is vital that spikes are not allowed to propagate from one unit to the next.

Syfer’s application specific MOV planar arrays are typically built into military style filtered connectors, including circular shell sizes 8 to 24, Arinc 600 and 404 series, as well as rectangular 24308 series and regular, subminiature and micro D types. Planar array technology has the added advantage of weight and volumetric efficiency over other transient protection or capacitor devices.

MOVs are suitable for protecting against several types of transient event. With a material response time of less than 500ps, no leads/tracks, and a low inductance geometry MOVs are more than capable of suppressing lightning induced transients. The devices are also ideal for protection against voltage spikes caused by power supply glitches and noisy switching circuits.

Operating over the full military temperature range from -55°C to +125°C, the devices are specified with leakage current of 5µA at +25°C, 50µA at +125°C, and with maximum working voltages from 10 to 45Vdc, and 7 to 35Vac.

Capacitance, measured at 1Vrms at 1kHz, depends on working voltage, planform, hole size and unit thickness, but typically ranges from 3nF at 10Vdc, 7Vrms to 500pF at 45Vdc 35Vrms. In operation, the MOV acts as a high value resistor, such that once the voltage reaches a certain value, the device becomes highly conductive and provides a fast and efficient short circuit route to ground to limit surges or pulses, and dissipating potentially destructive energy as heat. With the MOV Planar Array’s inherent capacitance, it can be used as a simple C filter or as one half of a Pi or unbalanced Pi filter.

When used together with Syfer’s Capacitor Planar Arrays, the MOV planars can provide a complete over-voltage transient protection and EMI filtering solution to connector manufacturers. Devices are RoHS compliant.

Syfer works closely with OEM customers and connector manufacturers to provide custom products meeting exact requirements. Manufactured at Syfer’s Norfolk, UK facility, raw materials are in stock and a secure supply is readily available. Orders are manufactured to demand, with a typical lead-time of 8 weeks. Prices start from £5, depending on specification and volume of order.