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Conditioning -v- protection

Rob Morris, UK country manager for Powervar UK, explains what a power conditioner can offer that a surge protector doesn’t.

Conditioning -v- protection

What we commonly call a surge is more accurately defined as a high voltage transient or impulse. Since a surge protector merely diverts this impulse away from any sensitive electronic systems, the term ‘surge diverter’ would be more accurate.

Surge diverters commonly use one or more of several electronic components, including metal oxide varistors (MOVs), silicon avalanche diodes (SADs), and gas tubes. All surge diverters have a voltage threshold, or clamping voltage. If the voltage rises above the threshold, impulses are shunted across the diverter to another pathway; once the impulse voltage falls below the threshold, the diverter stops conducting. Surge diverters also vary in the time - the clamping time - taken to respond to an impulse and in the different amounts of energy they can handle without being destroyed.

What happens when a surge diverter operates is the key issue. Where does the surge go and what are the effects of sending it there? The answer to this question, along with the inherent functional limitations of the surge diverters are the key differentiating factors between surge diverters and power conditioners.

Power conditioners defined
In simple terms, a power conditioner is any device that provides all the power protection elements needed by the technology it is protecting. This broad definition focusses attention on the fact that today’s electronic systems require different protection from their predecessors.
The linear power supplies used by older generation computers required voltage regulation.

However, modern microprocessors are powered by switch mode power supplies (SMPS) which are technologically quite different. SMPS are immune to voltage regulation problems but require protection from impulses, power line noise and, most importantly, common mode voltage.
Microprocessors make logic decisions with reference to a clean, stable ground. Common mode (neutral to ground) voltages disturb this reference and result in lockups, lost data, and unexplainable system failures.

Surge diverters function by diverting disturbance energy to ground. In the process, they convert a destructive disturbance into a disruptive one. Meanwhile, since the surge protector allows substantial energy to pass on to the microprocessor, there is still a risk of degradation by the residual surge energy.

This explains why, in so many instances, a user experiencing catastrophic hardware failure will install a surge diverter only to find that failures, while fewer, still occur and that the system now behaves unreliably at times.

A power conditioner for a state-of-the-art system incorporates three elements - a surge diverter, an isolation transformer, and a powerline noise filter. This approach provides several operational benefits. Isolation transformers permit the bonding of neutral to ground on the transformer secondary which means that the surge diverter can now divert surge energy to ground without creating a common mode disturbance in the process.

Since noise filters also function by diverting EMI and RFI to ground in the same manner, their performance is also enhanced by combining them with an isolation transformer.

An elegant tool
Transformers are an elegant power quality tool. Their secret is in their unchanging secondary impedance. Surge diverters can interact with the impedance of the building wiring in a way that makes their performance unpredictable. Noise filters suffer similar fates. However, when combined with the fixed secondary impedance of the isolation transformer, their performance is not only predictable but also controllable and repeatable by design. Surge protectors limit transient impulses to hundreds of volts. Power conditioners limit the same transients to less than half a volt.
In conclusion… Surge diverters are only capable of limiting damage from destructive events. Power conditioners eliminate system destruction, component degradation, and operational disruption. Surge diverters create common mode voltage. Power conditioners eliminate it. The differences between the two technologies are measured in system reliability, dependability, and performance.

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