Components help contend with EMI, RFI
A variety of components including capacitors, inductors, active filters, and cables and connectors can help your products meet EMC regulations and ensure your customers experience error-free operation. Our December1 and January2 issues covered test equipment that can help you identify EMC problems and highlighted some components that can help prevent EMC problems or solve problems that tests have identified. Since those issues went to press, several capacitors, filters, transformers, and even a touch-screen controller have emerged to further contend with EMI and RFI issues.
For example, at electronica 2014 in November, Würth Elektronik eiSos rounded out its EMC offerings by adding certified electrolyte, ceramic, and film capacitors (Figure 1) to its portfolio. X2 class (2,500-V peak) foil capacitors released at the show work with the company’s line of filters. MLCC capacitors are available in 0402-1812 sizes. The company highlighted aluminum-polymer capacitors in SMD and THT configurations, offering various advantages including the longest specified working life in their class.
Courtesy of Würth Elektronik eiSos
The company also showcased the WE-MAPI powder iron SMD inductor, which features, according to the company, the “world’s smallest metal alloy power inductor footprint.” The base of the device is 1.6 x 1.6 mm; the height is 1 mm. The magnetically shielded inductor offers high conductivity with rated currents up to 1.9 A, with saturation currents up to 4.9 A. In addition to the WE-MAPI, the company presented numerous additional families of inductors for power applications and switching controller designs.
Also at electronica, KEMET introduced automotive-grade film capacitors. The F862 Metallized Polypropylene Film Class X2 Series is specifically designed for safety applications subject to harsh environmental conditions such as high humidity.
The F862 Series, available in capacitances up to 4.7 μF and rated voltages up to 310 VAC, features fully approved RFI X2 capacitors for noise filtering and peak voltage protection when connected parallel to the mains or in series such as in a smart meter. New design enhancements resist traditional capacitance-loss mechanisms, allowing for long-term high stability. In addition, the F862 Series meets the Automotive Electronics Council’s AEC-Q200 qualification requirements, passing 1,000 hours life testing at 85°C with 85% relative humidity at rated voltage of 240 VAC.
Active filter modules
And in December, TDK introduced the EPCOS LeaXield active filter module for the minimization of earth leakage currents in power drive systems with frequency converters (Figure 2). Leakage current can cause residual current devices (RCDs) to trip. In some applications, this means that RCDs with low thresholds such as 30 mA cannot be used or only used with substantial additional expense. The LeaXield active filter module is connected between the RCD and the EMC input filter of the converter in standard three-phase industrial power grids and does not require an additional power supply.
Courtesy of TDK
LeaXield detects the common-mode currents on the load side via a current-sensing transformer. An amplifier generates an inverse of the leakage currents and feeds them to the power line via a capacitor network, producing almost complete cancellation of the leakage currents. LeaXield now is designed for rated currents up to 150 A for three-phase grids at frequencies of 50 Hz to 60 Hz and a rated voltage of 520 VAC. The new active filter can be used in systems with leakage currents up to 1000 mA.
In addition to minimizing earth leakage currents, LeaXield active filter modules also can improve the EMC performance of power drive systems in the range to approximately 500 kHz. The new active filter module achieves typical common-mode attenuation values of up to 30 dB at 4 kHz, 40 dB at 10 kHz, and 15 dB at 150 kHz.
The EPCOS LeaXield module can be retrofitted into existing converter-based installations to improve the EMC and RCD compatibility of the power drive system. Moreover, LeaXield circuits can be integrated into new EMC filter solutions to downsize the expensive current-compensated filter chokes.
HDBaseT transformers
Also in December, Pulse Electronics introduced its HDBaseT transformers (Figure 3), which provide common-mode noise reduction for improved EMI performance and isolation for power over HDBaseT (PoH) applications. Pulse Electronics’ HD8004FNL and HD8005FNL transformers are qualified for Valens chipsets VS100/010/020/202.
Courtesy of Pulse Electronics
Pulse Electronics is a member of the HDBaseT alliance. HDBaseT technology enables the 5Play feature set, which includes ultrahigh definition 4K video, audio, 100BaseT Ethernet, various control signals, and up to 100 W of power on a single 100-m/328-ft CAT5e/6 Ethernet cable.
“HDBaseT technology is a breakthrough for uncompressed HD video transmission,” explained Muhammad Khan, product manager at Pulse Electronics, in a press release. “Pulse transformers are an integral part for clear signal transmission, especially when teamed with a Valens chipset.”
Pulse Electronics HD8004FNL and HD8005FNL transformers are RoHS compliant and meet IEEE 802.3af stand-ards. They come in a 13.72 x 14.99 x 5.72-mm, 24-pin SMT package and are available in trays or tape and reel.
In related news, L-com Global Connectivity announced that it now is manufacturing panel-mount USB cables with ground wires. These USB 2.0 cables can be used inside a box or enclosure. By adding a ground wire, the user has the option to electrically ground the USB female connector to a panel or enclosure.
The molded panel-mountable construction is rugged—employing 20 AWG power conductors and 28 AWG twisted-pair data conductors all under a double shield for maximum EMI resistance.
The new USB cables are available in lengths from 0.3 to 3 meters. Each assembly includes two 4-40 x 3/8-inch Phillips pan head mounting screws. The #6 spade lug attaches to a screw or similar hardware. Common applications that use panel-mountable USB cables include PC peripheral interconnects, test and measurement and data acquisition instruments, and portable data storage and printer interfaces.
And finally, Zytronic is addressing EMI resistance with its ZXY110 touch controller. The company says this product’s key attribute is industry-leading resilience to EMI. This capability to combat EMI comes from the new touch controller’s smart frequency-scanning function in which the operating frequency moves dynamically between 1.3 MHz and 2.5 MHz to avoid detected environmental noise that otherwise would prevent the detection of touch events.
References
1. Nelson, R., “Test and component makers address ESD, EMI concerns,” EE-Evaluation Engineering, December 2014, p. 22.
2. Nelson, R., “Vendors target conducted, radiated immunity,” EE-Evaluation Engineering, January 2015, p. 27.
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