KEMET Says its New Three-phase EMI-RFI Filters Feature Industry-best Efficiency
The company’s fresh GTX series, measuring 250 x 120 mm, marks a 50% improvement in volumetric efficiency over competing devices, KEMET says.
Looking to better aid engineers in the suppression of electromagnetic conductive noise in both general purpose inverters and medical power supplies, KEMET last Tuesday introduced its GTX series of metal box, three-phase EMI-RFI filters, whose nanocrystalline cores enable excellent attenuation characteristics despite the filters’ compact size, the company said.
Sporting a broader frequency range, the series’ members are also light weight and offer a limited footprint thanks to their high mechanical density, the company noted in a press release.
The GTX series. Image used courtesy of KEMET
The fresh devices can handle three-phase voltages of up to 500 VAC, and come with current ratings of either 30, 40, 50 or 60 A. To support a variety of equipment topologies, customers can choose from six different Y capacitor setups at each of the four current ratings; there are 10, 47, 68, 100, and 470-nanofarad (nF) models available, with a capacitor-less option rounding out the selection.
Leakage currents range from 0.03 milliamps with no Y capacitor up to 92 mA with 470 nF Y capacitors. For those interested, full specifications for all 24 filters are available in the series datasheet.
In three-phase systems, there are three separate legs of AC sine wave inputs. The inputs are of equal magnitude, but are 120° out of phase with each other.
All three inputs are referenced to the same ground.
Inside the Filters
The GTX series is designed to control both common mode and differential EMI and RFI for three-phase power systems. The series datasheet provides performance graphs, illustrating the noise elimination achieved for all 24 possible Y capacitor/current rating combinations.
A GTX series circuit diagram. Image used courtesy of KEMET
In the diagram above, the three separate inputs, one for each phase, attach at input 1, 2, or 3. The ground attaches at point E. Cy represents one of the aforementioned Y capacitors.
What are Y Capacitors and X Capacitors?
Working for our sister site, All About Circuits, Nick Davis described X and Y capacitors in detail in a technical article, "Safety Capacitors First: Class-X and Class-Y Capacitors." These specially constructed units are aimed largely at devices like the GTX series, purposed to AC line filtering.
Image used courtesy of KEMET, via All About Circuits
As illustrated, the failure of an X capacitor will cause a short circuit, and if the circuit is not fuse-protected, a fire could be sparked. If a Y capacitor fails, ground protection is compromised and there is danger of electrical shock.
Davis's article also delves into considerations OEMs such as KEMET must face when selecting Y capacitors.
Applications include machine tools, industrial robots, inverters, power storage, process automation, medical devices, and diagnostic instruments.
GTX series filters are RoHS and Reach–compliant.
All series members are UL, c-UL, and TÜV–approved.
These filters operate over a temperature range of -25 to +55 ℃. Beyond 55 ℃, current handling capacity begins to derate, reaching zero at 105 ℃.