Technology Blog

A scaled prototype high-voltage pulsed modulator was built for an Inertial Electrostatic confinement (IEC) neutron source. Using a pulsed voltage modulator to power the neutron source offered many benefits including compact size, efficiency, reliability, and variable output control. The neutron source required a pulsed electrical potential of 120 kV and a current of 10 A. The pulse width was required to be variable between 50µs and 1ms at a duty factor of 5%, resulting in a pulse repetition frequency ranging from 1 kHz to 50 Hz, respectively. The modulator design was based on a diode-detected solid-state Marx modulator architecture developed at Los Alamos National Laboratory. This scaled prototyped had an output voltage of 13kV (1/10th scale) and an output current of 10A. A unique feature of the project was the implementation of snubberless design. All tests on the prototype were performed without traditional R-C-D snubbers for switch protection. Switch protection was provided solely by the self-snubbering architecture of the solid state modulator. Tests were performed with an additional 22µh inductance added to the load and no switch failures occurred. (1)
The modulator was built using 10 individually tuned stages. Each stage of 1300V utilized a single SBE Power Ring charging capacitor with symmetrically aligned tabs for low inductance and SBE’s patented Pulse Technology for extreme current pulse survivability. The additional feature of dry film construction simplified the construction and greatly increased the power density.
One of the capacitors used in the project will be displayed at the SBE Booth, at the upcoming 18th International IEEE Pulsed Power Conference, in Chicago, June 19-24, 2011. SBE senior application engineers will be available to answer questions and give more specific details of the design methodology and how these features can be put to work in making your most challenging design successful.
(1) Taken form a report titled “Pulsed Modulator for an IEC Neutron Source” – G E Dale, PPS 2007.

This unique module will be on display later this month and for the first time at the upcoming PCIM Europe conference in Nuremberg, Germany at all three booths of Danfoss, Methode and SBE Inc.
Indeed, SBE, Inc. has teamed with Methode Electronics and Danfoss Semiconductor to develop an integrated 67.5 kW capacitor/bus/switch power module concept. The design incorporates an SBE 700D349 (600V 500 µF) capacitor with a Danfoss E+ module with a bus and cooling structure from Methode. This concept illustrates vertical integration to reduce the volume of the inverter and provides a basic building block for scalability to higher power levels.
The SBE Annular Form Factor Power Ring Film Capacitor^TM provides a very low ESR and ESL along with the highest possible ripple current rating for a given capacitance value. The capacitor shares a cooling plate with the semiconductor module, which can utilize the Danfoss Shower Power^TM cooling technology to achieve higher ratings. The Methode hermetic laminar bus structure provides a reliable interconnection with much lower inductance than traditional layouts.
Come and visit us at the PCIM Europe conference, Nuremberg, May 17-19, at the following booths:
Methode Electronics – booth 766, hall 12
Danfoss – booth 325, hall 12
SBE – booth 247, hall 12

For any DC link application, knowing what the capacitor safe operating condition is for the desired reliability is critical. After months of engineering development, SBE has now developed a “state of the art” system, which used with the SBE advanced capacitor simulation tool and life test data will provide customers with invaluable data.

 In a typical DC link application, the film capacitor rating is defined by the internal winding hotspot temperature.  The sophisticated temperature rise testing system SBE develops helps characterize capacitor performance subject to realistic ripple current and cooling scenarios.  A power amplifier is used to drive a coil which is air-coupled to a secondary coil in the capacitor test loop.  The resonant frequency of the test loop is defined by the coil inductance and a series capacitor of much lower value than the test specimen.  Typically, a resonant frequency of approximately 20 kHz is selected, which is higher than the typical value of an automotive DC link. 

The capacitor under test is instrumented with thermocouples and connected to a laminar bus structure which interfaces to the test loop.  The capacitor/bus assembly is installed between two temperature controlled plates such that single or double sided cooling can be evaluated for steady state ripple currents up to 300 A rms.   The thermocouple data is then correlated with the SBE advanced capacitor simulation tool and life test data to define a safe operating condition for the desired reliability.

If you have a DC link application and are looking to understand the capacitor safe operating condition, whether it is for a Power Ring or a competitive product, talk to our engineering team!