Capacitors define the capabilities of today’s power electronics systems

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In recent years, the role of power electronics has become crucial in industrial automation and high-efficiency energy systems. Power capacitors help to improve the reliability and operating life of these systems. Read on to discover the latest developments in this field.

By Shruti Mishra

The primary function of power electronics devices is to manage, control and transform electric energy accurately in terms of voltage, frequency, current and waveforms. These devices, therefore, depend on passive components such as power capacitors that possess a relatively high specific energy as compared to the standard variants. The good thing is that these power electronics capacitors are capable of withstanding up to one million charge and discharge cycles without significant wear out, thereby helping the power electronics devices to meet the challenging standards that are being set for them today.

In the sections that follow, we will take a look at the technological advances that have happened in this field till now, and also look at the latest launches that are based on these technologies.

Technologies involved
Depending on the dielectric material used, capacitors are broadly divided into fixed and variable types. With miniaturisation being the order of the day, designers of power electronics devices are opting for fixed power capacitors because these are capable of storing a large amount of charge in a small form factor. In fixed power capacitors, the three basic dielectric materials that are used for power electronics devices are aluminium electrolytic, plastic film and ceramic.

Power capacitor applications

  • Electric power sector (in power generation and distribution)
  • Industrial equipment (motors, pumps and drives)
  • UPS systems to back up short power failures and cover high peak demand
  • Power transformation in EVs and automobiles
  • Electronic household products
  • Power conversion (like UPS systems, inverters, converters, etc)
  • Power quality monitoring and improvement (like harmonic filters, power factor correction)
  • Power generation systems like windmills and PV solar plants
  • Capacitive voltage dividers
  • Induction heating equipment

According to industry veterans, the most popular power capacitor among these three is the plastic film capacitor. Anil Bali, vice president, Deki Electronics, says that high voltage film capacitors are swiftly replacing high voltage ceramic capacitors because, first, they offer high insulation resistance (nearly ten times more than their ceramic counterparts) and second, they have a very low loss factor, which is almost 30 times less than that of a ceramic capacitor.

“Ceramic capacitors are somewhat non-linear in their frequency and voltage responses, compared to film capacitors. Another issue with ceramic capacitors is that they tend to behave as microphones do, picking up ambient sound and modulating the voltage across them, accordingly. Film capacitors are quite linear and usually better suited for analogue signal processing,” Bali points out while listing the benefits of high voltage film capacitors.
Poornima Hinduja, CEO, Desai Electronics—a company engaged in manufacturing of plastic film capacitors, says that several technological improvements have happened in this space over the past few decades. “Nowadays, the self-healing designs of film power capacitors are employing metallised polypropylene films in place of all-polypropylene films, and dry construction is swiftly replacing oil impregnation designs,” she says. She adds that as devices are now becoming lighter, the film power capacitor casings are making use of flame retardant, UL approved plastic casings wherever possible, in place of the metallic casings.

Market scenario
According to a new GIR (Global Info Research) study, the worldwide market for fixed power capacitors is expected to grow at a CAGR of roughly 2.8 per cent over the next five years, and will reach US$ 2.2 billion in 2023, up from US$ 1.87 billion in 2017.
Experts believe that the demand for such capacitors will continue to rise in the coming years as power electronics is finding many more applications. And the power levels of these capacitors will also increase sharply through technological innovations.

Products available in the market

Model: High voltage film capacitors, Manufacturer: Deki Electronics
Deki has come out with a range of film capacitors with 1kV and 2kV ratings. These capacitors are designed using film or foil inductive construction, with aluminium foil as the

electrode and plastic film as the dielectric coated with flame-retardant epoxy resin. The main application areas of these capacitors are in oscillators, timing and LC/RC filter circuits, high frequency coupling of fast digital and analogue ICs, etc.

Key features

  • Capacitance value: 100pf to 10nf
  • Maximum temperature rating: 100°C
  • Climatic category: 40/100/56
  • Applicable specifications: IEC 384-13

Contact: www.dekielectronics.com

Model: E66, Manufacturer: Electronicon Kondensatoren GmbH
With a lower temperature limit of up to -50°C and complete hermetical sealing, the new E66 series (design W) from Electronicon is good for harsh operating environments. Filled with neutral insulation gas, these capacitors are environment-friendly, can be mounted in any position and have up to 20 per cent less weight than their equivalents with resin filling, the company claims. The PD-strength of the E66 design outperforms the classical PK16 range by a factor of two.

Key features

  • Highest RMS current rating: 120A per unit
  • Can material: Aluminium filled with solid PU resin
  • Humidity class: C

Contact: www.electronicon.com

Model: DC link capacitor, Manufacturer: Desai Electronics Pvt Ltd
A DC link connects a rectifier and an inverter. These links are found in converter circuits and in VFD circuits. The DC link is the connection between these two circuits, which is usually known as the DC link capacitor. This is connected in parallel between the positive and the negative conductors. This capacitor prevents the transients from the load side going back to the distributor side.

Key features

  • Reference standard: IEC 61071
  • Capacitance: 100μF to 2800μF
  • Capacitance tolerance: ±5 per cent, ±10 per cent
  • Rated voltage: 450V to 2000V DC
  • Operating temperature: -40°C to 85°C / -40°C to 105°C
  • Life expectancy: 100,000 hours at rated voltage and a hotspot of <70°C

Contact: www.deccapacitors.net

Model: TRAFIM, Manufacturer: AVX
The TRAFIM series is specifically designed for DC filtering applications such as DC link or resonant filters for voltages up to 6000V. A high specific energy of up to 390J/l (along with reliable and controlled self-healing technology) makes this series particularly suitable for power converters in the areas of renewable energy and power transmission. The controlled self-healing technology is based on a high temperature grade metallised film impregnated with vegetable oil, allowing an operating temperature of up to 95°C.

Key features

  • Capacitance range: 110μF to 10600μF
  • Tolerance: ±10 per cent
  • Working temperature: -55°C/+95°C (according to the power dissipated)
  • Dielectric film: Polypropylene
  • Rated DC voltage: 1850V to 6000V

Maximum RMS current: Up to 400ARMS

Contact: www.avx.com

 

 

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