Current Sense Transformers Information
Current sense transformers are used to detect and measure current. There are two basic types of products: switch-mode transformers for power conversion applications, and precision-measurement transformers for instrumentation applications. Current sense transformers for power conversion applications are used to measure trends, peak values and average values rather than absolute values. These devices are efficient and dense, but do not offer a great amount of accuracy. They are available in a variety of shapes and styles, and are can support most traditional manufacturing processes. Current sense transformers are certified and approved by the American National Standards Institute (ANSI), the Canadian Standards Association (CSA), the International Electrotechnical Commission (IEC), Underwriters Laboratories (UL), TÜV Rheinland/Berlin-Brandenberg (TUV), and Verband Deutscher Elektrotechniker (VDE). Products sold in European Union (EU) nations must comply with the Restriction of Hazardous Substances (RoHS) and Waste Electrical and Electronics Equipment (WEEE) directives.
Performance specifications for current sense transformers include operating frequency range, rated direct current (DC) or root mean square (RMS) current, direct current resistance (DCR), isolation or high potential (hipot), operating temperature, and largest dimension. Rated DC current is the level of continuous direct current that can be passed through the transformer winding without damage. This current level is based on the maximum temperature rise at the maximum, rated ambient temperature. Rated DC is related to the transformer’s ability to minimize the power losses in the winding via a low DC resistance. For low-frequency currents, the RMS current can be substituted for the rated DC current. Direct current resistance (DCR) is the resistance of the transformer winding as measured with DC current. The DCR is usually minimized in transformer’s design and specified as a maximum rating. Isolation or hipot level is the maximum voltage that can be applied to current sense transformers without breaking the winding of the transformer or the dielectric.
There are many package types and packing methods for current sense transformers. Surface mount technology SMT) adds components to a printed circuit board (PCB) by soldering component leads or terminals to the top surface of the board. Through hole technology (THT) mounts components on a printed circuit board (PCB) by inserting component leads through holes in the board and then soldering the leads in place on the opposite side of the board. Connectorized transformers attach with coaxial or other types of connectors. Waveguide assemblies consist of a hollow metallic conductor with a rectangular, elliptical or circular cross-section. Integrated circuit (IC) package types for current sense transformers include flat pack (FPAK), single in-line package (SIP), dual in-line package, and small outline integrated circuit (SOIC). In terms of packing methods, current sense transformers can be packed in trays, tubes, or tape reel assemblies. Bulk-pack products are distributed as individual parts.
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