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.
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.
Power supply Technical Center certified to ISO 13485 – the first ever in Japan
Press Release July 20, 2020
TDK Corporation (TSE 6762) is pleased to announce that TDK-Lambda Japan received ISO 13485:2016 Medical Devices – Quality Management System – certification for the TDK-Lambda Nagaoka Technical Center (Nagaoka City, Niigata Prefecture, Japan). This is the first time a standard switching power supply manufacturer in Japan has received ISO 13485 certification and brings the group total to five locations. The scope of this latest registration covers the Design/Development, Manufacturing and Servicing Activities (Analysis, Repair and Overhaul for Field Returns) of Components (Switching Power Supply) for Active Medical Devices. Now, five of TDK-Lambda’s major development, design and production sites in Japan, the United Kingdom, the United States of America, China, and Malaysia have been certified. This enhances the Group’s capability to provide products and services to the global medical device market.
TDK-Lambda has focused on the medical device market, developing a large portfolio of medically certified products to the international IEC 60601-1 standard. Adopting ISO 13485 provides a practical foundation for manufacturers to address the Medical Device Directives, regulations and responsibilities. It demonstrates a commitment to the safety and quality of medical devices.
To read the entire press release, please see this link.
For more information about TDK Lambda – or to discuss your power requirements – please contact Cover 2 Sales.
TDK Lambda has recently released the compact CUS400M series of single-output AC/DC power supplies. The supplies offer either 12V or 24V DC output with 15V, 19V, 28V, 36V and 48V versions to follow. The CUS400M is packaged in the industry standard 3″ x 5″ footprint and can deliver 400W with forced air cooling.
The CUS400M can be used in both Class I and Class II (no earth wire) applications and offers efficiencies of up to 94%.
An option board providing a 5V 2A or 12V 1A standby voltage, remote on/off, remote sense, DC OK signal and AC fail signal is also available.
Mechanical options include metal base plate, U channel, cover and top mounted integral fan.
Safety certifications include IEC/EN/ES 60601-1 and IEC/EN/UL 62368-1 with CE marking for the Low Voltage, EMC and RoHS Directives. The units comply with EN 55011-B and EN 55032-B conducted and radiated emissions and meet the EN 61000-3-2 harmonics, IEC60601-1-2 Edition 4 and IEC 61000-4 immunity standards.
Typical applications include medical (B and BF type), home healthcare, dental, test and measurement, broadcast, professional audio and industrial equipment.
For more information about the CUS400M power supplies, to discuss your power needs, or to request a sample, please contact Cover 2 Sales.