Credit to Author: Anne-Sophie Moresco| Date: Thu, 28 Mar 2019 12:00:24 +0000

As countries, organizations, and individuals continue to look for every opportunity to reduce their environmental footprint, it’s more important than ever to have reliable ways to control the energy we use. There’s no better way to reduce energy use than to turn off loads when they’re not needed. In the bigger picture, it’s also important that we find ways to reduce every kind of waste. Continuing to move toward a ‘circular economy’ means getting more life out of the equipment we use and, in turn, reducing replacement.

Electrical contactors are ubiquitous devices, found throughout the power distribution systems of industrial, commercial and residential buildings. They’re in constant service, turning on and off power to all sorts of loads, such as lighting, heating, roller blinds, watering systems, ovens, utility motors (e.g. ventilation or heat pumps), and more. Acting as the remote control interface to electrical circuits, contactors play an important role in managing facility operations, business processes, and occupant comfort. They are also a key part of the coordinated control needed for a successful energy management program.

The perils faced by contactors … and loads

Every day, a typical contactor will open and close a circuit many times, making and breaking all power supply lines running to one or more loads. A contactor must endure this frequent switching over a long period of service.

Contactors have come a long way in terms of robust design. For example, some may include features to help suppress the arc produced when interrupting motor currents. Many also have excellent electrical, opposed to mechanical, endurance. This is typically specified in number of total switching cycles over the product’s lifetime. And, of course, contactors, as part of a safety chain, will need to comply with all relevant safety standards.

However, the conditions that contactors operate in can sometimes be more harsh than manufacturers have designed for. And even under the best conditions, the repeated switching of a contactor will naturally begin to erode the metal contact points of each pole over time, due to arcing and heat. The ability to endure repeated switching, under the specific conditions of the application, will define the lifespan of a contactor.

When a contactor eventually fails, one of two things typically happens:

1. A set of contacts deteriorate to the point that they stay open, causing a constant open circuit. This is usually the result of combination of chemical pollution and harsh temperature.
2. Overheating welds the contact points together, forcing a constant closed circuit.

For a 3-phase system in a buildings, it’s common to choose a contactor with three individual poles, one for each phase, plus a switched neutral pole. If the neutral pole fails by no longer making contact, it will cause an open-neutral condition. This can cause up to 400 Vac to occur between phases, which can be a serious hazard to sensitive loads.

New contactor design protects LED lighting

Many types of loads can be put at risk by overvoltage, especially electronic loads like smartphone chargers, tablets, computers, TVs, and fridges. In addition, LED and compact fluorescent lighting loads are especially sensitive to overvoltage.

What can exacerbate the problem is that LED luminaires require a large start up current, which can put further stress on the contacts of a contactor. Add to this the significant levels of harmonics generated by LEDs that can cause further heating of a neutral pole. These challenges spell a potentially shortened lifespan for contactors in these applications.

With lighting representing 32% of energy consumption (and cost) in an average office building, and LED technology being 75% more efficient, LED lighting will continue to replace other technologies at an increasing rate. So it’s critical that the reliability of lighting circuit switching be addressed.

Meeting this challenge head-on, one of the newest innovations in contactor technology is a reinforced neutral pole. By desynchronizing the neutral pole and giving it a more robust connection, a contactor will be able to endure greater stresses, especially in single-phase, group controlled LED lighting circuits. This will not only help extend the lifespan of the contactor, it will also help avoid a neutral break condition that could put LED loads at risk.

Schneider Electric now offers a contactor with reinforced neutral pole as part of its Acti 9 iCT range. The model 3P+N offers a choice of 40 and 63 A ratings, each with options for NO or NC operation. The contactor is compatible with the Acti 9 comb busbar system and can be combined with a variety of auxiliary control, protection and indication functions, as well as offering simple integration with automation schemes. For more information, download the data sheet for the new 3P+N contactor of the Acti 9 iCT range.

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