Power Electronics

Renewable Energy Sparks Component Development

The rapid growth in renewable energy systems, particularly solar- and wind-power systems, is creating demand for specialized power components. Some of these devices are required for pitch control or braking in wind turbines, while others are needed in the power inverters that connect the energy source to the grid. Among the parts being developed for these applications are several passive power components that are exemplified by recent introductions from three vendors.

Power Resistors for Wind Turbines

As applications in wind-power generating systems evolve, the need increases for power resistors that meet the stringent needs of the various parts of the turbine sub-systems for functions like braking and inrush current protection. Beyond its off-the-shelf power resistors, Tyco Electronics (www.tycoelectronics.com) also offers custom-designed resistors.

Power ratings range from 1 W to greater than 1 kW, with wire-wound, thick and thin film, foil, carbon and ceramic structures. The company offers a variety of packaging options, as well as special cases and configurations. Options on cooling systems, custom lead formations, matched resistance solutions, custom windings and foil technology in stamped or etched solutions are also available. In addition, a variety of product insulations and coatings for a range of ceramic cores in rods, tubes or flat substrates are offered.

The customization and development program includes in-house product testing. The range of tests can be designed in conjunction with customer specifications to include cyclic rated power and overload testing, adiabatic (single shot and frequency) testing, environmental, mechanical and repetitive pulse testing. Qualification testing is carried out to a proven procedure and the product development stages are well-documented and approved by a design approval team. For more information on custom power resistors, contact Tyco Electronics' technical support center at (800) 522-6752 or e-mail [email protected].

The power resistors are part of the company's recently announced portfolio of products developed specifically for wind-power applications. Other products in the portfolio include the HVS Connector System. Developed for energy, industrial and rail applications, this system accommodates fiber, coax and signal contacts, as well as high voltage and high current with ratings up to 5000 V and 250 A.

The portfolio also has custom high-voltage power distribution cable assemblies that provide interconnects for the power generation and control systems, both in the wind turbine nacelle and in the tower. In addition, the company is offering high-current contactors with continuous current ratings of up to 500 A at 320 Vdc, for power-switching applications typically found in the switchgear, pitch and yaw drives, and generators of wind turbines.

The company notes also that its CORCOM brand three-phase filters are well-suited to wind-power applications as the inverter-to-grid interface and the control electronics for the inverter.

Film Capacitor for DC Filtering

From Cornell Dubilier, the Type 947C high-current medium-power film capacitor provides dc filtering up to 1200 Vdc, making it suitable for IGBT power filtering and dc-link inverter applications needing lower bus capacitance and high ripple current (Fig. 1).

DC link capacitors provide both bulk energy storage and ripple-current filtering, and many inverters are designed with excess aluminum capacitors across the bus to handle the ripple-current requirements. The 947C's higher voltage and current handling readily allows it to replace aluminum electrolytic capacitors in dc link applications that can use lower bus capacitance as is typically the case with inverters designed for wind energy, solar and fuel cell applications supplying to the grid.

“The cost per amp of ripple current for film capacitors is about one-third of that of aluminum capacitors.” says Scott Franco, marketing manager at Cornell Dubilier Electronics.

With its segmented metalized polypropylene film technology, Type 947C handles currents up to 72 A at frequencies up to 20 kHz, and it is rated for ripple currents up to 100 kHz and peak voltages up to 1800 V. Capacitance is up to 730 µF at 800 V, 470 µF at 1000 V and 320 µF at 1200 V. The compact case is a 90-mm aluminum cylinder electrically isolated from the capacitor and in lengths of 97, 120, 145 and 170 mm. Capacitors come with a choice of M5 threaded insert terminals or M8 threaded stud terminals on the top and an optional M12 mounting stud on the bottom.

Full specifications are at www.cde.com/catalogs/947C.pdf. Or for more information, contact Brian Padelford at (508) 996-8564. In OEM quantities, Type 947C capacitors are available with pricing from $35.

Compact Chokes for Solar-Power Inverters

SMP Sintermetalle Prometheus (www.smp.de) of Graben-Neudorf has introduced compact chokes for use in solar-power inverters (Fig. 2). The chokes operate quietly, which allows their use in residential areas. The materials used have low magnetostriction and very low eddy current and hysteresis losses, enabling high inverter efficiency.

SMP supplies chokes and filters for frequencies up to 200 kHz and current ratings up to 1000 A, with component sizes ranging from 36 mm to 300 mm diameter and weights from 50 g to 130 kg. All components are manufactured to customer specifications using in-house developed powder composites. Components can be made to all common standards, including protection type IP20 and IP65. All products are RoHS- and WEEE-conformant and the materials used are UL-listed. For more information, contact Westendorf Associates at (262) 641-9730 or visit the company online at www.westendorfassoc.com.

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