Why electrical equipment fails in a freeze

Ampthill, UK – Electrical equipment manufacturers often overlook the effects cold weather can have on the operation of products, resulting in widespread failures the moment the mercury falls below zero, according to power supply company PULS UK.  

Power supplies used to run equipment outdoors such as motorway message screens and railway signaling are particularly vulnerable in freezing temperatures. This is because the high voltages generated inside the units, which can reach as much as 400 Volts, create sparks between conducting parts formed by ions present in condensation, resulting in severe damage and premature failure.

Engineers at PULS, which has a range of power supplies designed specifically to operate in temperatures as low as minus 40°C, say many of these failures could easily be avoided by applying conformal* coating to internal components to prevent the formation of condensation.

Low temperatures also cause problems during start up due to a component known as a NTC (Negative Thermal Coefficient thermistor). Put simply this means that the lower the temperature the higher the resistance and most power supplies use this to limit the inrush current when the power is turned on.

However, if the resistance is too high the power supply won’t start, along with the device it supports.  PULS has developed unique inrush prevention technology to overcome this problem and allow start ups in the most extreme conditions.

“Manufacturers need to consider carefully the conditions their products are likely to operate in and make sure the power supply they specify is up to the job,” said PULS UK MD Harry Moore. “A unit that will work perfectly in normal conditions could be totally useless in freezing weather and we’ve all seen the results when someone gets it wrong.”