At present, the renewable energy market is entirely dependent on power electronics. As the world gradually shifts to clean energy, the need for this technology is also intensifying. As a result, the building blocks of power electronics such as capacitors are also witnessing a steep increase in demand.
By Shruti Mishra
Power electronics is an umbrella term that comprises systems that are used in controlling and converting the flow of electrical energy. In any power electronics system, it is very important to deliver the precise amount of power needed at a given time. To ensure this happens efficiently, these systems make use of passive components including capacitors that play a crucial role in power electronics based energy conversion. The size of the capacitors matter a lot when determining the performance of power converters. Bulky capacitors increase the size, weight and volume of power converters.
However, in recent times, the capacitor technologies for power electronics have improved considerably, not only resulting in an increased operating temperature range and reduced sizes but also enhanced reliability.
Before taking a look at some of the latest launches, let’s find out what type of capacitors are used in some crucial power electronics applications.
Electric vehicles (EVs)
What is making electric vehicles a more accepted form of public as well as personal transport is the widespread adoption of power electronics. The systems or components that made these environment-friendly vehicles a reality have all undergone a major revolution. Capacitors in EVs perform the task of preventing the ripple currents from reaching back to the power source. They also smooth out DC bus voltage variations. But the most important function capacitors perform in EVs is to protect the semiconductor. Earlier, they used to protect thyristors in the circuit, but now they protect the IGBT.
Type of capacitor used: The ability of metallised film capacitors to overcome internal defects has made them the most preferred choice for electric vehicles.
Motor drives
This is one of the oldest applications of power electronics. Power systems for heating, ventilation and air conditioning (HVAC) need power electronics inverters to vary the speed of the motor drives, thereby making the process more efficient and reducing the amount of energy consumed.
Type of capacitor used: The best suited variants for power electronics inverters are the snubber capacitors. Snubbers dissipate power from the switch to the resistors very efficiently and therefore reduce the total losses during switching.
Power converters
Power electronics converters make it possible to transport electricity over long distances with minimal power losses. These are basically used to transform alternating current (AC) into high-voltage direct current (HVDC) and vice-versa. HVDC transmission lines are becoming more popular these days because they are much smaller and need less space compared to the AC lines for the same power capacity.
Type of capacitor used: These days, DC link capacitors have quite efficiently replaced the electrolytic capacitors used in power conversion techniques due to their high electrical standards. These capacitors provide three times higher dielectric voltage strength and have a very low dissipation factor.
Latest products launched in the market
Model: IGBT snubber capacitor, Manufacturer: Deki Electronics
Snubber capacitors have undergone many changes in construction, which enable increased power handling and short circuit tolerance. Their self-healing property and polypropylene film ensure low self-induction, high rupture resistance and high reliability. The dielectric often used in such capacitors is polypropylene film, because it has a low dissipation factor that permits high AC currents with low self-heating, and it performs well over the temperature range and frequencies in power electronics applications.
Application areas: Deki’s IGBT snubber capacitors are used in high voltage, high current and high pulse applications such as IGBT protection circuits, snubber networks, protection circuits in SMPS, and for energy conversion and control in power electronics.
Key features
- Dielectric: Polypropylene film
- Operating temperature range: -40°C to 85°C
- Capacitance: 0.047µF to 5.6µF
- Rated voltage: 700V DC to 3000V DC and 380V AC to 750V AC
- Dissipation factor at 25°C: ≤0.0005 at 1kHz
- Insulation resistance: 3000 after 1 minute of electrification at 100V DC
Contact: www.dekielectronics.com
Model: GCS series of capacitors, Manufacturer: Globe Capacitors
Capacitors from the GCS series are cylindrical or oval, and have an aluminium case that incorporates a safety mechanism, which offers long life and reliability. The thin metal layer deposited on the surface of the dielectric makes these capacitors self-healing and prevents momentary voltage surges from causing permanent voltage breakdown. Mounting these capacitors at the application end ensures that free air space is provided under a fault condition. The expansion clearance will be 16mm at the minimum.
Application areas: These capacitors are mainly used in air conditioners and gas ovens.
Key features
- Capacitance tolerance (standard): ± 5 per cent
- Climatic category: 40/85/21 in accordance with IEC 60068-1
- Dissipation factor (at 20°C): 0.2 per cent
- Rated frequency: 50Hz to 60Hz
- Safety class: P2
- Insulation voltage (terminal to case): 2000V AC
- Safety standards: UL 810
- Compliance with Canadian Certificate Mark for performance and safety in accordance with CSA
Contact: www.globecapacitors.com
Model: MKP1847H, Manufacturer: Vishay Components India Pvt Ltd
The Vishay Roederstein MKP1847H is the industry’s first, full-range AC filtering film capacitor series to withstand demanding temperature humidity bias (THB) testing — 85°C, 85 per cent RH for 1,000 hours at rated voltage — without altering its electrical characteristics, company sources claim.
The MKP1847H series of capacitors is designed to ensure stable capacitance and ESR values over a long service life while operating under harsh environmental conditions. These devices are ideal for input and output filtering in outdoor renewable energy inverters and critical applications such as UPS systems for sensitive data centres. The MKP1847H series of capacitors feature segmented film and offer a low ESR down to 3mΩ. They also provide high ripple current capabilities up to 24.5A.
Application areas: These capacitors are well suited for UPS systems, renewable energy, AC harmonic filters and for welding equipment.
Key features
- Dielectric: Polypropylene film
- Rated capacitance range: 1µF to 35µF
- Capacitance tolerance: ±10 per cent, ±5 per cent
- Maximum continuous AC voltage (50Hz/60Hz) range: 250V AC, 310V AC, 350V AC, and 480V AC
- Climatic testing class: 40/105/56 B
- Rated temperature: 85°C
- Maximum permissible case temperature: 105°C
- Reference standards: IEC 61071, IEC 60068 and UL810
- Electrodes: Metallised dielectric
- Self-inductance: <1nH per mm of lead spacing
Contact: www.vishay.com
Model: DC link capacitors, Manufacturer: Desai Electronics Pvt Ltd
Desai Electronics has launched DC link capacitors that connect a rectifier and an inverter in the converter and variable frequency drive (VFD) circuits. These capacitors help to prevent the transients from the load side going back to the distributor side. They also serve to smoothen the pulses in the rectified DC. These capacitors offer high life expectancy and low self-inductance.
Application areas: The capacitors are used in UPS systems, wind power inverters, solar power inverters, traction and industrial drives and in induction heating equipment.
Key features
- Basic reference standard: IEC 61071
- Capacitance range: 100µF to 2800µF
- Capacitance tolerance: ±5 per cent and 10 per cent
- Rated voltages: 450V DC to 2000V DC
- Operating temperature range: -40°C to 85°C and -40°C to 105°C
- Dissipation factor: ≤ 2 X 10^-4 at 1kHz.
- Test voltage between terminals: 1.5 X rated voltage V DC for 60 seconds
- Life expectancy: 100,000 hours at rated voltage and < 70°C hotspot
- Failure rate: 50 to 100 FIT
- Permissible RMS ripple current: 30A to 100A
- RoHS compliant
Contact: www.deccapacitors.net
Model: Snubber capacitors, Manufacturer: Desai Electronics Pvt Ltd
Desai Electronics’ snubber capacitors eliminate the voltage transient and ringing that occur when the switch opens (off) by providing an alternate low impedance path for the current flowing through the circuit’s intrinsic leakage inductance. Thus, these snubber capacitors are used to protect high frequency switching devices like IGBTs.
Application areas: These capacitors are mainly used in photovoltaic and wind inverters, motor drives, frequency converters, welding power supplies, hybrid vehicle inverters and electric vehicle chargers.
Key features
- Reference standard: IEC 61071
- Rated capacitance: 0.1µF to 33µF
- Capacitance tolerance: ±5 per cent and ± 10 per cent
- Rated voltages: 1000V DC, 1200V DC, 1500V DC and 2000V DC
- Operating temperature range: -40°C to 85°C
- Climatic category: 55/85/56
- Dissipation factor: ≤ 5 x 10^-4 at 1kHz
- Test voltage between terminals: 2.5x rated voltage DC for 10 seconds
Contact: www.deccapacitors.net
Model: E61, Manufacturer: Electronicon Kondensatoren GmbH
The E61 series comprises highly reliable, energy-efficient and low inductance capacitors that are widely used these days. They can even work in low power DC links. With their pin terminals, these capacitors can be integrated directly into printed circuit boards.
The capacitors in the E61 series are optimised for high RMS and surge currents. Along with their high specific ratio of capacitance to volume, they offer long-term stability and storability, as well as self-healing without loss of capacitance.
Key features
- Voltage range: 500V DC to 5000V DC
- Maximum current: 35A to 80A
- Minimum temperature: -50°C
- Maximum continuous temperature: 95°C
- Maximum relative humidity: 95 per cent
- Inductance: <9nH
- Warranty: Two years
- Electrical conductor material: Brass and copper
- Insulation type: Dielectric film, resin and plastic
- Electrical test for qualification: IEC EN 61071/61881
- Applicable regulations and standards: RoHS, UL94-V0, UL810
Contact: www.electronicon.com
Model: DC capacitor MKP type, Manufacturer: Deki Electronics Pvt Ltd
The use of DC link capacitors intensified after inverters became popular in the white goods electronics industry. In inverter based devices, these capacitors function as a short-term current source and sink to limit the transient voltages seen by power conversion semiconductor switches and the input DC bus.
These capacitors are constructed with low inductive wound cell elements of metallised polypropylene film, potted with resin in a flame retardant case.
Application areas: These capacitors are used for high ripple current modules in frequency converters, industrial and high-end power supplies, and solar inverters.
Key features
- Dielectric: Polypropylene film
- Electrodes: Metallised films
- Capacitance range: 0.47µF to 60µF
- Reference specifications: IEC 61071 and IEC 60068
- Climatic category: 40/100/56
- Lifetime expectancy: >100,000 hours at UNDC and 70°C
- Maximum operating temperature (case): 105°C
Contact: www.dekielectronics.com
