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More to cables that meets the eye wire
Cables are widely disregarded as mere bundles of wire. Yet they are the vehicles that transport energy and information and the signals they carry lend them an identity.
However, they are also prime sources of electromagnetic disturbance. It might stem from the way that they interact. Or from the mortal coils inside them.
Cable management systems are one way of attenuating and even eliminating it.
But in all cases, thinking ahead and taking a few elementary precautions can go a long way to controlling the electromagnetic emissions that cause problems ranging from noise to data corruption and process downtime.
Foil tour coils with TVS to protect the integrity of your communications
We might have entered the wireless world, but it’s still crawling with cables. There are bundles and bundles of them in panels. And where there are cables there are transient disturbances. Lots of them – high-frequency disturbances that affect communication links and corrupt information.
Why so many transient disturbances?
Because in 80% of cases communication cables have no protection. “Hey,” says the customer, “this is just an ordinary relay. Why is it wreaking havoc in my installation?”
The answer is almost always “because of your coils”.
In plants and buildings, the noise that affects communications like VOIP mostly happens when a relay opens and closes. That noise is electromagnetic disturbance that originates from the coils. In fact so much trouble stems from coils in the relays, I call them “decisional coils”. They’re the decisive factor.
One transient that can be devastating is arcing. It occurs mainly in DC systems where the voltage doesn’t drop to zero. When the contact opens to disconnect the coil and break the current, the current tries to return to the power source. The result is arcing, which can unleash tremendous energy. And of course it impacts on your communication links and can make the frames worthless. There are protections. A blowout coil affords protection against arcing. It stretches the arc till it breaks. You could also have a dedicated parallel circuit against overvoltage.
So why do many end-users have no overvoltage protection?
They don’t see the bigger picture. They see just clean bright relays and contactors and think “I don’t need protection”. But real life is a dirty business, and electromagnetic disturbance dirties communications. What’s more, designers don’t bear in mind the importance of protecting coils.
Of course, the overriding reason is cost. Yet a coil costs only a few tens of euro cents. Put that against the cost of the losses caused by an information and communication system that fails.
Yet most of the time the source of the problem is the ordinary coil.
Protecting your contacts against arcing doubles and even triples their life expectancy and protects against irritants like noise and disasters like system failures. And in the world of communication where megabytes of information can be lost in microseconds, it simply makes sense to have voltage surge protection.
Does transient voltage surge protection really make a difference?
Yes. The two illustrations below tell the story.
Transient voltage surge suppressors (TVS) which should be fitted in parallel with the coil. They are outside devices, which you can open and remove as you need. And always install them as close to the coil as possible.
TVSs range from resistors to varistors and TVS and freewheeling (or let-through diodes). They dissipate the energy stored inside the coil. All work with DC systems. The fastest are TVS and freewheeling diodes. But the technical ins-and-outs are another story.
What matters here is that when you use a relay or contactor, mainly in DC systems, always protect your communication cables – especially in sensitive applications. For dependability and safety.
I think a lot of users don’t bother with protection because they assume that any system component is plug’n’play. But if they don’t protect their installation, they’d better plug’n’pray.
What to know more about transient protection? Tell us about your mishaps with coils? Or want to know about TVS devices?
