The following article was originally written by James Tabbi, Deputy Vice President for Exxelia’s Magnetics Business Unit
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 with Exxelia, please contact Cover 2 Sales to arrange a call with an Exxelia engineer.
Recently, Boyd Corporation published a technical article in Electronics Cooling Magazine. This article covered innovative Ultra-Thin Vapor Chambers (UTVC’s) and how they enable new generations of Mobile, Portable, and Wearable devices and with a competitive advantage in the marketplace. As mobile devices advance it is vital to understand how new, thinner, more powerful cooling technologies are essential to continued industry growth and better performance.
The trend of improved thermal management in thinner and lighter form factors is not a trend relegated to just mobile devices, It is pervasive across all major industries. As part of Boyd’s dedication to forward-thinking and keeping our customers well-informed, this article gives a good foundation on these emerging thermal technologies that are solving challenges in new industries
In addition to this white paper, Boyd has publizhed technical details on TiVC’s in this datasheet.
If you have any questions on UTVC’s or other thermal technologies, please contact Cover 2 Sales. We can set up a a technical discussion with one Boyd’s engineers to discuss how to best address your thermal challenges.
EMC Live On-Line Seminar
Including a Presentation from XGR Technologies
“Space-Saving Board Level EMI Shielding”
Announcing “EMC Live” – an exciting online event scheduled to take place on September 1, 2020. This is a one-day webinar event focused on IoT, Wireless and 5G EMC. Lean more about EMC Live here.
XGR Technologies will be one of the presenters, delivering a 20-minute webinar on an innovating EMI shielding solution that delivers reduced board space, lighter weight and lower in profile.
XGR Technologies’ presentation will begin at 1:45PM EDT. You can register for their seminar with the following link:
XGR’s presentation will demonstrate how a unique board level EMI shield can enable the board designer to save up to 75% in board space in the trace width around the shielded cavity perimeter. In addition to space savings around the perimeter, you will learn how non-traditional choices in material selection can result in the lowest profile, lightest weight board level shield technology in the market.
XGR Teechnologies is the manfuacturer of the Snapshot® EMI Shielding technology. Originally developed by W.L. Gore & Associates, the SnapShot products are manufactured by XGR using the same materials on the same equipment by the same people that have been making SnapShot parts for the past 15 years.
For more information about XGR Technologies, the SnapShot solution or solving EMI problems, please contact Cover 2 Sales.
This blog article discusses the solutions from American ZETTLER that are capable of switching or isolating high voltage circuits operating at 480VAC. This ranges from bulky definite-purpose contactors, which handle the higher power loads more commonly associated with 480VAC circuits, down to miniature power (latching) relays popular in lighting.
These robust switches offer safety approvals and certified ratings well suited for a number of applications including refrigeration, air conditioning, heating, elevators, food service equipment, cranes, hoists, welding machines, power supplies, vending machines, lighting, pumps and compressors.
Perspective: A smaller XMC0 contactor next to AZSR1200, AZSR190, AZ2800, and AZ576 power relays.
25-90 FLA up to 600VAC
125-450 LRA at 480VAC
Make/break 40A, carry up to 200A, 920VAC (85°C)
50 make/break cycles up to 200A, 920VAC (85°)
For more information about American ZETTLER’s switching products, please contact Cover 2 Sales.
When an AC-DC power supply’s input voltage is interrupted the DC output will only remain within regulation for a short period of time. This is specified on the power supply datasheet as the hold-up time. During this hold-up time the power supply relies on energy stored in its capacitors to maintain operation.
Hold-up time is important in certain vertical markets. The medical industry’s concern regarding hold-up time has increased since the release of the EN 60601-1-2; 2015 (Ed4) immunity standard. Primarily created to address the growing number of products used in home healthcare, this standard specifies multiple AC voltage dips ranging from 20 msec to 5 seconds. The longer outages are addressed by batteries or by designs that ensure no harm will occur to the patient or operator if the power supply output voltage drops out of the regulation band.
Airborne equipment is covered by the DO-160 standard. Section 16 of the standard refers to power input, simulating conditions of aircraft power from before engine start (using auxiliary ground based power) to after landing, including emergencies. The requirement is for a hold-up time of at least 200 msec.
In a recent article on their Power Supply Blog, TDK Lambda explores power supply hold-up time: What it is, where it’s important and, most importantly, several technical approaches for extending hold-up time. You can read that article here.
If you would like to discuss extending hold-up time in your system, contact Cover 2 Sales so that we can arrange a conversation with a TDK Lambda applications engineer.