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Best DC link capacitor in the world? Power Ring from SBE

Power-ring-capacitor spray-end-diagram

How good is a Power Ring capacitor?

The Power Ring design results in lower losses, lower inductance and a higher ripple current rating than traditional film capacitor technology. The ring shape provides extremely low internal losses (ESR) and dramatically lowers the inductive properties (ESL). SBE’s Power Ring capacitors show ESR values as low as 0.15 mOhm for a 1000µF – 600V DC Link.

The graph of temperature versus ripple current (above) illustrates the huge improvement in thermal performance delivered by the Power Ring design versus a conventional array of film capacitors. This performance improvement translates to a more efficient use of microfarads where high ripple current is an issue. Design can be optimised for current-handling rather than having to “bulk up” on capacitance only for current handling survival and lifetime requirements – a strategy which has the side-effects of increased cost and size.

How do they do it?

The ultra-low ESR is achieved by shortening the current path between the electrodes. SBE’s patent-pending segmented end spray approach divides the metal end spray into “floating” segments (see diagram). Unlike conventional capacitors, the loss between film and end spray metalisation is so low that current in the end spray can be the dominant loss contributor. The capacitor element ESR can be as low as 50μΩ and the ESR of the end spray/braid can be less than 10μΩ.

Power ring v snubber capacitor

A Power Ring DC link capacitor with integrated bus bar offers a loop inductance that can eliminate the need for a snubber circuit. Snubber capacitors get very hot since they are connected to the IGBT pins (often the hottest point other than under the die itself) and are almost never directly cooled due to the difficulty of connecting cooling plates. Their small size and poor cooling mean snubber capacitors are usually the weak link in the reliability chain for an inverter.
As usable operating voltage increases there can be a tendency to add a snubber to get every bit of safe operating voltage out of a system. The integrated Power Ring capacitor is a more effective method of reducing overshoot, and therefore increasing safe operating voltage, without compromising reliability or system lifetime.

In short…

A cooler DC link capacitor means a longer lifetime. A lower ESL means reduced overshoot and undershoot which reduces stress. Removing the requirement for a snubber capacitor means lower costs, a smaller design and a longer lifetime.

Useful links

Power Ring capacitors

GT series – snubber capacitors

KPST series snubber capacitors

Capacitors from PPM Power


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ESP high pulse load resistor


Compact solution for high power pulsed applications

ESP resistors from EBG provide a highly compact solution for high power, pulsed, low frequency applications such as:

  • Inrush current limiting
  • Capacitor pre-charge and discharge
  • Motor control units
  • Power supplies,
  • Battery charging systems
  • Inverter drives.

Right now, these resistors are popular in electric vehicle subsystems as pre-charge resistors and in-rush current limiting devices for industrial power control systems.

ESP resistor

Large energy pulses

The special resistive element provides a highly reliable, non-inductive current path capable of handling large energy pulses up to 3300 joules over one second.

Small footprint

The EBG ESP resistor has a very small footprint when compared with thick film, ceramic and wire wound resistors with equivalent peak power ratings, an essential feature for applications where where space is very limited such as electric vehicles or military systems.

Resistor technology comparison table

Resistor Technology Peak Power Rating Physical Size
Thick film + x
Wire wound ++ xxxx
Ceramic +++ xxxx
EBG ESP +++ x

Superb build quality

The resistor has superb build quality with large end caps and M4 threads for multiple mounting options. Two diameter sizes are available: 14mm and 20mm. Both sizes are 62mm in length with resistance values between 10 ohms and 1K ohms. Tolerances are +/-5% or +/-10%. If you require tighter specifications please contact a member of the PPM Power technical sales team on 01793 784389.

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LeClanché equivalents to obsolete Epcos MKV (B25835) caps

TDK / EPCOS have now withdrawn their MKV (B25835) series of capacitors which are based on polypropylene in oil – now a rather outmoded technology. For customers seeking a replacement, LeClanché supply dry film caps using the latest metallised polypropylene film technology. In most cases these represent a drop-in alternative yet provide all of the advantages of film technology due to LeClanché’s unique design and innovative manufacturing process.

  • No hazardous materials
  • No liquids
  • Self-healing film
  • Mount in any position
  • Very long lifetimes
  • “Soft” landing at end-of-life

Examples of LeClanché equivalents for EPCOS B25835 MKV series

TDK / Epcos / Siemens Capacitor Leclanché Capacitor Voltage Capacitance
B25835K1105K7 PAM 150-1.0 cv4 (K) 1.5kVAC 1µF
B25835M0104K007 PAM 140-010 cv4 (K) 1.4kVAC 100nF
B25835M6474K007 PAM 90-047 cv4 (K) 900VAC 470nF
B25835K2104K007 PAM 340-010 cv4 (K) 3.4kVAC 100nF
B25835M0105K007 PAM 140-1.0 cv4 (K) 1.4kVAC 1 µF
B25835M6225K7 PPM 160-2.2 cv4 (K) 1.6kVAC 2.2 µF
B25835M0225K007 PAM 140-2.2 cv4 (K) 1.4kVAC 2.2 µF
B25835-M474-K7 PAM 140-047 cv4 (K) 1.4kVAC 470nF
B25835M2474K7 PAM 340-047 cv4 (K) 3.4kVAC 470nF

This is not an exhaustive list. Please contact PPM for more information.

Capacitors from PPM Power


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New 300W HV DC-DC converter modules

The PH-A280 series of high voltage input DC-DC converters from TDK-Lambda are now available with 300W output. The DC-DC power modules have a range of 200 to 425Vdc, and are suitable for use in applications using a 380V DC bus such as data centres, telecommunications and renewable energy. The four new models are rated at 12V / 25A, 24V / 12.5A, 28V / 10.8A and 48V / 6.3A. These extend the 50 to 150W PH-A280 product range which already includes outputs of 3.3V, 5V, 12V, 24V, 28V and 48V. 

Greater Adjustment Range

The 300W models have a greater adjustment range of -60% to +20% to accommodate non-standard voltages and can provide full load with -40°C to +100°C baseplate temperatures.  The range offers efficiencies of up to 92%,

Hardware Format

The units follow the industry-standard half-brick package (61.0 x 12.7 x 57.9mm).


The converters can also be conduction cooled making them suitable for use in sealed outdoor enclosures or liquid cooled applications.

Five year warranty

All PH-A280 modules include:

  • Five-year warranty,
  • Remote on-off
  • Over-current and over-voltage protection.


The series is fully isolated with an input to output isolation of 3,000Vac.

Environmental certification

Certified to IEC/EN 60950-1, UL/CSA 60950-1 with CE marking for the Low Voltage and RoHS2 Directives.

Useful links

High Voltage DC-DC power supplies

Overview of power supplies available from PPM


PHA-280 Datasheet

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Why use nanocrystalline magnetic material?

Nanocrystalline image

Nanocrystalline is a soft magnetic material composed of 82% iron which has been dubbed the future of magnetic materials in power electronics.  Higher permeability means lower loss transformers, which can translate to large reductions in size and weight.

Lower losses, smaller size and reduced weight

The losses of a Nanocrystalline core can be up to two-thirds less than an equivalent Nickel Supermalloy core and up to 80% less than for toroid geometries. Less power is dissipated by the transformer (or inductor) and means the size of cooling components can be reduced.

Ease of switch over from other materials

Nanocrystalline can be formed into any shape and therefore offers a drop-in replacement for existing cores manufactured from other materials, such as Supermalloy or ferrite.

Nanocrystalline v Supermalloy

Nanocrystalline material is more suitable than Supermalloy in applications such as high frequency/broadband transformers, broadband current sensors, high frequency filter chokes and pulse transformers because nanocrystalline offers:

  • High permeability over a broad frequency range
  • High saturation flux density
  • Low losses

Soft magnetic cores from PPM Power

PPM Power can supply tape-wound soft magnetic cores manufactured by MK Magnetics from a range of materials, including grain-oriented silicon steels, 50% and 80% nickel alloys, amorphous material, cobalt alloys and nanocrystalline. Cores up to 1.8m x 1.8m / 1800Kg and strip widths up to 0.6m are possible.

potential magnetic core weight reductions based on material

Potential magnetic core weight reduction (2000 Gauss, 20kHz)

Comparison of magnetic materials

Material Losses Saturation Permeability
Grain Oriented Silicon Steel x ***** ++
Standard Crystalline Permalloy xxxxx **** ++
Advanced Silicon Steel xxxx *** +++
Fe-Amorphous Steel xxx **** +
High Performance Ferrite xxx * ++
Advanced Crystalline Permalloy xxx ** ++++
Co-Amorphous Alloys xx ** +++
Nanocrystalline Alloys x **** +++++

Feature image in homepage newsreel is by Kapsid_Schema-01.jpg: Gleiberg derivative work: Hic et nunc – derived from  Kapsid Schema-01.jpg: , CC BY-SA 2.0 de, Link

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Single pin HV connectors now prefabricated with 30kV cable assembly

GES high voltage connector S series news image

GES connectors have announced that the S-series of single-pin high voltage connectors is now available prefabricated as a cable assembly. With all electrical connections potted, there is no air in the terminations. This reduces partial discharge (micro-sparks) which means lower noise and longer lifetimes. The S-series is a premium-quality single-pin connector for classic high voltage applications such as HV outputs on high-voltage power supplies.

The S series is available in four variants for operating voltages from 10 to 40 kVDC (testing voltage 15-60 kVDC) at a rated current of up to 30A*. A shielded 30 kV quality cable is used to a cable length specified by the customer.

GES Electronic & Service have supplied connectors for a multitude of high voltage applications worldwide.  GES HV connectors are exceptionally reliable, long-lasting and well-engineered.

High voltage connectors

S-series single-pin HV connectors

*max. continuous current 40 A, surge current 3000 A.

GES 10kV high voltage connector HSB10

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New 350W ultra-high power resistor

EBG have expanded the UXP series of ultra-high power resistors to include the UXP350. Using thick-film technology, the UXP series has an operating temperature range of -55°C to +150°C and a maximum working voltage of 5kV DC. Higher voltages and other temperature coefficients are available on request. Resistance tolerance is+/- 5% to +/-10%.

Often used as a snubber resistor to compensate for C-R peaks in traction power supplies, the UXP series is also intended for use in speed drives, power supplies, control devices and robotics. The UXP portfolio covers power ratings from 300W to 2000W.


UXP350 datasheet

UXP2000 ultra high power resistor from EBG

About EBG resistors

EBG has been a leading manufacturer of non-inductive thick film resistors since 1977. The manufacturing process is state-of-the-art, producing precision resistors for high voltage, high power, and pulse loading applications.

The EBG product range consists of over 350 standard and custom models of high voltage resistors, power resistors, pulse resistors, current sense resistors, load resistors, high power resistors, and matched divider resistor sets. Form factors available include cylindrical, flat, TO220, TO247, SOT227  and many custom power footprints. Normal lead time for standard or custom products is 8 weeks or less.

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New 3.2kW three-phase AC-DC power supply

TDK-L-TPS3000 AC-DC industrial power supply newsreel image

PPM Power can now supply a series of 3-phase AC-DC power supplies delivering up to 3200W in a 2U package. The TPS3000 series from TDK Lambda operates from a wide range Delta or Wye 350 – 528Vac 3-phase input, avoiding the requirement for step-down transformers and assisting phase load current-balancing. Models are available with a nominal voltage of either 24 or 48v.  The 24V model can deliver up to 3200W at 133.3A. The power supply isolation is 3kVac input to output, 2kVac input to ground and 500Vac output to ground.



  • Isolated AC fail,
  • DC-good and dropped-phase signals,
  • Remote on/off,
  • Remote sense
  • 12V 0.3A standby supply.

Ideal applications

  • Test and measurement
  • Lasers
  • RF power amplifiers
  • Semiconductor fabrication.

Other information

  • Parallel Operation – up to eight units can be connected in parallel for higher power and internal ORing FETs allow redundant operation.
  • High efficiency over a wide temperature range – the 92.5% efficient unit can operate at full load in ambient temperatures of up to 50°C and deliver up to 55% load at 70°C.
  • Cooling – internal temperature-controlled fan to reduce noise.
  • Case dimensions – 107 x 84.4 x 324mm (W x H x D) – suitable for 2U high racking systems
  • Standards compliance – All models certified to UL/CSA 60950-1, IEC/EN 60950-1 and carry the CE mark for Low Voltage and RoHS2.
  • Radiated emissions – complies with EN55022-A and meets the IEC 61000-3-2 harmonics, IEC 61000-4 immunity and SEMI F47-0706.
  • PMBus™ communications interface – allows remote monitoring of output voltage, output current, internal temperature, status signals and fan speed. In addition, output voltage, overcurrent limit and remote on/off can be programmed via the PMBus™. Output voltage can also be adjusted between 19.2 – 29V and the current limit point by 70-105% using front panel potentiometers or an analogue 0-5Vdc voltage.

Useful links

TPS3000 product page

Low voltage AC-DC industrial power supplies

PPM power supplies page.

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PPM awarded Investors in People – GOLD

Investors in people feature image

Investors in people gold logo

PPM is awarded Investors in People – GOLD

Pulse Power and Measurement Ltd (PPM) has been awarded the Investors in People Gold standard, joining the top 14% of accredited organisations across the UK who believe in realising the potential of their people. PPM was established in 1994 and employs 35 people. In 2014, PPM were awarded the investors in people silver award after the first assessment.

PPM’s Business Divisions

PPM Power – High voltage, pulse power and power electronics – www.ppmpower.co.uk

ViaLite Communications – RF over fibre equipment for communications – www.vialite.com

PPM Test – Electromagnetic compatibility (EMC) test equipment – www.ppmtest.com

PPM Systems – Antennas and RF systems for defence – www.ppmsystems.co.uk

Business improvement through people management

Investors in People is the UK’s leading accreditation for business improvement through people management. “We’d like to congratulate PPM on their Gold standard”, said Paul Devoy, head of Investors in People. “Such a high level of accreditation is the sign of great people management practice and shows an organisation committed to being the very best it can be. ”

stuart-at-work qi-at-work

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Intelligent gate drivers for silicon carbide MOSFETs


One of the few disadvantages of SiC MOSFETs is that the technology requires careful consideration of the gate driver circuit. But, an intelligent gate driver can provide a lot more than just optimised switching performance…agile-switch-silicon-carbide-mosfet-gate-driver

Silicon carbide – better than silicon

Silicon Carbide (SiC) MOSFETs have a number of key benefits over Silicon IGBT’s for high power applications such as battery charging, traction drives, induction heating, renewable energy inverters and welding. Switching and static losses are lower.  Reverse recovery losses are almost nil. Also, there is relatively little change in loss as switching frequency is increased, resulting in efficient operation at hundreds of kHz.  Moreover, SiC does not exhibit deterioration of these parameters with temperature unlike IGBT’s, avoiding the need to derate the current specification for operation at higher temperatures. System level efficiency gains are therefore available for lower cooling needs, higher power density and reduced size and weight.

Gate driver circuit needs consideration

Careful consideration must be given to the gate driver circuit to optimise the performance of the device. However, an intelligent gate driver can provide more than just optimised switching performance:

  • Active clamping (augmented turn-off) means lower switching losses, better protection and reduced ringing.
  • Advanced fault detection means enhanced reliability and better diagnostics
  • Configurability enables design flexibility, voltage protection and master/slave paralleling

Active clamping (augmented turn-off)

Inserting one or more intermediate levels in the gate voltage between on and off reduces ringing, switching losses and inductance-induced overshoot voltages. In a short circuit condition, this also helps reduces stress on the component.


Augmented turn-off uses one or more intermediate voltage steps to reduce ringing, losses and overshoots.


The two plots above contrast a conventional gate drive solution with augmented turn off. The result is a reduction in Vce overshoot from 700v to 500v.

Advanced fault detection

Temperature and high voltage monitoring – An intelligent gate driver provides the isolation and functionality to support monitoring of temperature and the DC link voltage. Sophisticated monitoring means effective diagnostics and ultimately translates to improved reliability. For example, both under-voltage and over-voltage protection can shield a SiC MOSFET from voltages that would impact its long-term reliability by pulling the gate to Vgs.

Overcurrent protection – Silicon carbide MOSFETs have only a limited capability to withstand short circuits. Therefore, response time is critical. Augmented turn-off also plays an important role in controlling the aftermath of a short circuit because the MOSFET is being shut down in a high current condition.


Software settings – Every inverter design is unique. An intelligent gate driver enables configuration of settings for :

  • Augmented turn-off
  • Undervoltage and overvoltage lockout
  • Desaturation detection
  • Dead time
  • Fault lockout
  • Automatic reset

Drivers are also configurable for parameters such as overcurrent, blanking time and response time.

Intelligent master/slave paralleling – High frequency switching requires precise synchronisation of input triggers to avoid current imbalances. Master/slave technology allows the drive signal to be split locally at the power module, resulting in better performance and reliability due to reduced propagation delay. Plug and play connectivity to slave drivers enables easy use and significant cost savings.


One of the few downsides of silicon carbide is that the gate driver circuit needs careful consideration. However, using an intelligent gate driver brings significant additional benefits such as lower switching losses, longer lifetime and reduced ringing, as well as configurability advantages such as design flexibility, voltage protection and master/slave paralleling.

View AgileSwitch intelligent gate drivers

agile-switch-fuji-product-catalog-3-638 agile-switch-fuji-product-catalog-9-638agileswitch-logo__v_PPM Power square logo

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More Information?

Telephone +44 (0)1793 784389 or email: sales@ppm.co.uk