What?! There is a capacitor in my transformer?
Get a quick tutorial from James Tabbi, our Deputy Vice President of Exxelia's Magnetics Business Units, explaining what's interwinding capacitance
Exxelia recently designed an auxiliary transformer for a spacecraft application, where interwinding capacitance was of concern to the customer. The controller chip they were using in their power supply was noted to be “rather sensitive to excess capacitance.”
Exxelia has also supplied thousands of driver transformers for use in a subsystem of the AN/TPQ-53 Radar System in which interwinding capacitance within the toroidal windings is held to a very demanding tolerance.
But what is interwinding capacitance?
Capacitance in a transformer winding cannot be avoided. The voltage difference between turns, between winding layers and from windings to the core, creates “parasitic” capacitances in the transformer circuit. These capacitances are shown as Cp, Cs, and Cw in this schematic diagram of an electronic transformer “equivalent circuit.”
Interwinding and distributed capacitance occur in transformers due to the physical separation of, and electrostatic coupling between, different turns of wire. In general, the capacitance presents itself between the different layers within a winding and between the outside layer of one winding and the inside layer of the next.
In conventional magnetics, interwinding capacitance is a function of coil configuration – the geometry of adjacent conductors and separating dielectric media. Specifically, it is directly proportional to the shared surface area of the windings (shown in green and red below), the dielectric constant of the insulator between the windings (shown in gray below), and is inversely proportional to the separation distance through the dielectric media.
In high-frequency transformer design, leakage inductance and capacitance are often competing design requirements since the beneficial parameters that provide low leakage inductance also tend to increase the interwinding capacitance.
Excessive capacitance can cause undesirable common-mode noise transmission between transformer windings or between transformer windings and core or another ground connection.
Exxelia can assist with these design challenges when creating products that have to deal with interwinding capacitance, for all types of magnetic components.
Important coil configuration design considerations must be made when capacitive coupling causes unacceptable signal transmission (for example, common-mode noise transmission or undesirable spurious ringing on a high voltage output). Windings may be configured in a way that reduces the dV/dt voltages induced across dielectric media. Conductive screen(s) tied to preferred potential(s) can also be added between adjacent windings to reduce transmission.
If you’d like to learn more about interwinding capacitance or would like to discuss your specific magnetics needs, contact us email@example.com
Exxelia will integrate a cobot into its manufacturing process
Exxelia has just equipped itself with a cobot (in partnership with the company Cognitive Engines) adapted to the production needs related to the manufacture of RF High Q capacitors. The cobot is a collaborative robot designed to work hand-in-hand with operators. This technology coupled with artificial intelligence (I.A) offers a multitude of advantages including: Quality improvement: The cobots are equipped with high performance sensors and integrated quality control systems, which allow 100% thorough visual inspection, and guarantee a high level of quality, while adapting to the movements of the operators (no occupational safety risk). Flexibility: Cobots are lightweight and adaptable. This versatility allows them to occupy different positions depending on the needs of the moment. Safety: Cobots are designed to be used in pairs with Exxelia operators and can therefore protect them from dangerous or arduous tasks, which greatly improves the quality of life at work (reduction of repetitive gestures; positive impact on musculoskeletal disorders ). Optimization of operator time: Cobots take care of low value-added tasks and let the operator focus on high-value tasks, which values the contribution of operators. By collaborating with operators, cobots can improve production quality and accuracy, while ensuring their safety. Industry 4.0 is changing the way businesses operate and the way products are designed, manufactured and delivered. Exxelia is convinced of the importance of Industry 4.0 and is positioning itself to be at the forefront of this transformation. As a company specializing in the design and manufacture of critical electronic components for industrial applications, Exxelia pays particular attention to maintaining its extensive know-how. Exxelia uses state-of-the-art technologies to ensure the high level of quality that the applications the group serves cannot be without. The group pays particular attention to the coexistence of robotization with the mastery of manual processes held by operators to continue to offer customers the highest quality products, while remaining competitive. Adopting this technology will allow Exxelia to maintain its leadership position in its industry, while improving quality, accuracy, operator safety and production efficiency.