Kingtronics International Company — Power Protection Expertise
In many high voltage and high frequency designs, the weak point is not the semiconductor, but the pulse capacitor or snubber capacitor sitting across it. Typical field issues include capacitors running hotter than expected, capacitance drift after repeated pulse cycles, unclear dv/dt capability, and difficulty reading derating curves in different operating conditions. When this happens, engineers often end up oversizing parts or adding extra margin “just in case”, which increases cost without necessarily solving the root cause.
Instead of starting from brand names, a more robust approach is to look at the underlying design: what does a high voltage film capacitor actually need to offer to survive in pulse and snubber circuits? Once those requirements are clear, it becomes much easier to check whether a given polypropylene film capacitor series really matches the application.
Typical Pain Points in Pulse and Snubber Capacitor Selection
In practice, engineers selecting a snubber capacitor or pulse capacitor often report similar pain points:
• The datasheet lists nominal voltage and capacitance, but gives limited guidance on how to interpret
temperature derating and frequency behaviour in real power stages.
• It is not always obvious whether the capacitor’s construction is non-inductive and suitable for
fast edges and high dv/dt.
• Dissipation factor and insulation resistance are given at one test frequency and
temperature, while the actual application uses very different conditions.
• For long-life designs, engineers need to understand how high voltage film capacitors behave over
thousands or millions of pulses, not just at a single test point.
These issues affect design choices in PFC stages, inverter legs, SCR commutation circuits, snubber networks, and electronic ballast or lamp driver circuits. The key question is always the same: how to map the datasheet parameters of an axial film capacitor to the actual stress in the application.
What Really Matters in a Pulse and Snubber Film Capacitor
When comparing different polypropylene film capacitor series for pulse or snubber use, engineers usually focus on a few core aspects rather than marketing descriptions:
• Dielectric and metallization: polypropylene is widely used thanks to its low loss and stable
behaviour. Designs using double-sided metallization can support more demanding pulse conditions
when correctly specified in the datasheet.
• Winding and inductance: a non-inductive film capacitor helps to control voltage
overshoot and ringing in fast-switching, high dv/dt environments.
• Rated voltage vs. operating profile: simply matching the DC or AC rated voltage is not enough.
Designers need to confirm how the usable voltage is derated with temperature and how this interacts with the
circuit’s worst-case conditions.
• Dissipation factor and heating: a low dissipation factor at the relevant frequency reduces
internal heating, which is important in high frequency capacitor positions.
• Insulation resistance and standards: parameters such as insulation resistance, climatic category
and reference standards (for example, IEC 61071 capacitors for certain pulse applications)
support a more objective comparison between different series.
Focusing on these points helps to narrow down candidate parts before any hardware build, which is especially useful when prototypes and qualification cycles are time-consuming.
Using Datasheet Curves Instead of Trial-and-Error
A common source of uncertainty is how to interpret graphs in the datasheet of a high voltage film capacitor. Curves of capacitance versus temperature, dissipation factor versus frequency, or insulation resistance versus temperature are often treated as “nice to have” rather than as hard design inputs. In pulse and snubber positions, however, these curves are exactly what show whether the device stays within its intended operating window.
By reading these charts alongside the rated values, a design engineer can estimate whether a given snubber capacitor or pulse capacitor is being used close to its specified limits or with an appropriate margin. This approach reduces dependency on trial-and-error and helps structure technical discussions between engineering, procurement and suppliers.
Example: Pulse and Snubber Film Capacitor in Practice
The short video below shows a practical example of a polypropylene axial film capacitor series used in pulse, snubber and high voltage applications. While every design has its own constraints, it can be helpful to see how a dedicated pulse/snubberseries is positioned and described at a high level.
Using the FKT Series Catalog as a Reference
For engineers who prefer to work directly from tables and curves, a consolidated film capacitor catalog is often more convenient than navigating multiple web pages. The FKT Series catalog groups together ratings, dimensions and ordering information for the family, including pulse-oriented options.
The following PDF provides a structured view of voltage ratings, capacitance ranges and mechanical formats within the FKT family:
How FKT-SA Aligns with These Requirements
Within this context, the Kingtronics FKT-SA Series is specified as a double-sided metallized polypropylene axial film capacitor with non-inductive configuration. According to the datasheet, it is referenced to IEC 61071, with climatic category 40 / 105 / 56 and an operating temperature range from −40 °C to +105 °C. Rated voltages are listed at 250 V, 400 V, 630 V, 1000 V, 1600 V and 2000 V, and the available capacitance range extends from 0.00022 µF up to 3.9 µF.
The datasheet defines a dissipation factor ≤ 0.0010 at 1 kHz and 20 °C, and specifies insulation resistance values at 20 °C and 100 V for different capacitance ranges. It also provides guidance on voltage derating above the nominal temperature points for both DC and AC operation. For engineers comparing pulse capacitors or snubber capacitors, these parameters can be used directly in the usual selection process alongside other high voltage film capacitor options.
If you are currently reviewing pulse or snubber positions and need a documented, IEC-referenced polypropylene film capacitor series to compare against your design targets, you can:
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