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Myths about Capacitors

When discussing power factor correction solutions with people across our industry, someone will often mention something about capacitors being unreliable, prone to catching on fire, or similar.

What follows is a list of the most common misconceptions about capacitors, and kVAr Solutions' response to them.

The capacitors will catch on fire.

Capacitors used to catch on fire, and there have been various brands available that were poorly engineered and under-rated. When the capacitor overheated, they would disintegrate and, yes, sometimes would burn. However, since 2010, MPP (Metalized Polypropylene) dry capacitors are required to be UL rated and will not burn. kVAr Solution’s capacitors actually contain a fail safe, where if the capacitor fails and overheats, the heat causes the resin to expand, breaking the electrical connection to the capacitor, thus isolating it from the electrical system.

MPP capacitors are unreliable.

Well, like anything, that depends on what you buy. kVAr Solutions only uses quality capacitors, either from Turkey or Germany. The EcoVAr range uses ELCO MPP caps, rated at >150,000 hours, and the ProVar and SmartVAr ranges use premium KBR MPP caps, rated at >250,000 hours. By comparison, active systems use capacitors with a maximum life of 100,000 hours – which are more easily affected by heat. Further to this, SVGs use electrolytic capacitors to reduce size and cost, and these are filled with corrosive liquids that can produce corrosive gases throughout operation. The capacitance values in conventional capacitor-based systems are much lower than in active systems, meaning there is an even lower risk to the capacitors.

Capacitor-based PFC systems produce excessive amounts of heat.

This one is simply incorrect. Active electronic systems produce more heat per kVAr delivered than conventional capacitor-based systems, and it is produced in a smaller space, so is much more difficult to dissipate. kVAr Solutions pays special attention to the thermal design of their systems to ensure optimal cooling is achieved – and we believe we have the best design in the business. For more information on this, read our article titled “Thermal Issues in Power Factor Systems.” Power factor systems will always produce heat, but with our systems, and in most conditions, they can be cooled by conventional airflow. If you can’t cool a conventional system, you sure as heck can’t cool an active one!

Capacitor-based PFC systems are physically huge.

While an active system may be shorter and narrower than a conventional capacitor-based system, they are usually deeper. Many of them are 800mm deep, which can cause issues in a lot of plant rooms. Our capacitor based systems are installed as standard in 600mm deep enclosures that will fit beside most industrial switchboard systems. Our most common model is only 2.1m high, by 800mm wide, and 600mm deep, with a maximum of 470kVAr.

Capacitor-based PFC systems can’t correct leading power factor.

Ok, so an SVG system is better equipped for correcting leading power factor. However, in most situations, the leading power factor is caused by a constant load, such as LED lighting, and is only a small part of the total correction required. You can add an SVG module to a capacitor-based system for a fraction of the price of installing a full sized SVG. This allows the capacitor-based system to do the ‘heavy lifting’ and coarse correction, while the SVG looks after the leading power factor and any spikes.

Capacitor-based PFC systems are slow and inaccurate.

This may be true for some capacitor-based systems, but it definitely is false when regarding kVAr Solutions’ systems. For many years, we have used Rapid Capacitor based technology, allowing target power factors of 0.99. We are constantly researching, and new developments are coming on board all the time. We can use Thyristor switches instead of contactors, which switch within 30milliseconds. Thyro switches also switch at the optimum time in the sine wave to reduce capacitor wear.

Hybrid systems are cheap imitations of SVGs.

kVAr Solutions was one of the first to develop a Hybrid system; and it is truly a level of technology and reliability above active electronic systems. As detailed in our article “Active versus Passive Power Factor Correction”, you get a system that offers the best of both worlds, with capacitors for the course correction and SVGs for the fine correction and leading power factor. kVAr Solutions hybrid systems are modular, and parts can be replaced easily by site electricians. With a modular SVG, we can offer 100% redundancy on all steps, meaning if there is a failure, the whole site does not lose its power factor correction. Recently, Hybrid systems have been released by SVG manufacturers – asserting them to be the perfect combination in cost-effective reactive power compensation.

Maintenance is expensive.

Compared with any other PFC, system maintenance is simpler, and components have a longer lifespan. MPP capacitors, contactors, and reactors all have shelf lives of decades – the parts are readily available, affordable, and easily stocked. This goes for kVAr Solution’s modular trays as well. Repairs and maintenance to kVAr Solutions’ capacitor-based systems can be carried out by any registered electrician. Our systems are also designed to operate with steps removed, so if part of the system is removed for servicing or maintenance, the system will continue to operate. Active systems are usually “return-to-base” when there is a problem – meaning the entire system is out of action for days or even weeks while it is repaired or replaced. In addition, most manufacturers state that spare parts older than 1 year cannot be used without first “reforming” the capacitors – a process of progressively applying voltage. kVAr Solutions uses high quality components with a long operational life. It is a general rule of thumb that you should budget between 2% to 5% of an asset’s replacement value in maintenance costs per year. From our service records, it is clear that most systems, if not all, are able to be serviced and maintained for less than that 2% of replacement cost.