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DC-Link Capacitors for Flat Designs

KEMET offers improved volume efficiency with its rectangular aluminum electrolytic capacitors.

Rectangular Aluminum Electrolytic Capacitors From KEMET

KEMET offers improved volume efficiency with its rectangular aluminum electrolytic capacitors. This shape means that there is no "lost" area around the capacitors compared to the conventional radial versions, which has a positive impact on the size of a design, especially when several capacitors are connected in series or parallel. Furthermore, the realisation of a flat design is made possible.

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An Alternative to Snap-In Electrolytic Capacitors

The internal structure is basically the same as a conventional Al electrolytic capacitor, except that the winding is flattened to obtain the rectangular shape. The AAR70/AAR80 series can be seen as an alternative to snap-in electrolytic capacitors, differing in the recommended mounting on the PCB. The capacitors can be mounted in any horizontal position or in an upright position. Depending on the number and arrangement of the required capacitors, horizontal mounting can either save footprint or implement a flat design. It is also possible to stack the capacitors. Here are some recommendations.

Increase of Lifetime and/or Ripple Current Capability due to Cooling

The capacitor is designed for mounting with or without cooling by a heat sink (the flat surface allows easy use of a heat sink). When mounting the capacitor on a metallic chassis, the ripple current capability is significantly improved, and the use of thermally conductive adhesive, paste or foil further improves the cooling conditions.

Depending on the load profile and cooling conditions, efficient cooling can increase the lifetime by a factor of 2-6. For an exact evaluation we will calculate the expected lifetime based on your mission profile.

The ripple current capability can also be significantly improved when the capacitor is mounted on the metal housing, using thermal paste due to the low thermal resistance.

Example:

AAR80-series (105°C/450V/270µF/1.89A rms at 100Hz, 105°C)
Capability at 85°C: 1.89A rms x1.6

AAR80-series (105°C/450V/270µF/3.93 A rms at 10kHz, 105°C)
Capability at 85°C: 3.93A rms x1.6

When cooled by heat sinks, the ripple current capability doubles. Thus the capacitor is capable for 6A rms at 100Hz and 12.5A rms at 10kHz.

The use of multiple capacitors stacked or in a bank configuration can change the thermal dynamics and thus the ripple current capability compared to a single capacitor. In such cases, please contact us for assistance.

The capacitor should not be mounted with the safety vent facing downwards. However, if the PCB is mounted vertically on the application, so that the capacitor is in a horizontal position, this position may be allowed.

The AAR80 and AAR70 series can withstand vibrations of up to 20g and 40g respectively. This vibration resistance is only achieved when the capacitor is stiff mounted to the PCB and/or metal case by gluing it to the PCB or case. The use of thermally conductive adhesive ensures efficient heat dissipation of the capacitor. If the capacitor case is allowed to move during vibration (with respect to the PCB), this can easily cause the wire terminals to break due to fatigue. A capacitor rigidly mounted on the PCB is crucial.

Furthermore, a rigidly mounted PCB with short distances between the mounting points is also required so that vibrations are not further amplified.

Typical application for this is the DC link in AC/DC power supplies or inverters for different ranges.

Specifications AAR70 series:

  • Operating Temperature: -40°C to +85°C
  • Rated voltage: 400 ~ 450VDC
  • Capacitance: 160µF ~ 360µF
  • Lifetime: 10.000h at 85°C, rated voltage and ripple current
  • Dimensions: 12x44.5x38.1mm ~ 12x44.5x57.2mm
  • Vibration proof up to 40g
  • AEC-Q200 qualified

Specifications AAR80 series:

  • Operating Temperature: -40°C to +105°C
  • Rated voltage: 450VDC
  • Capacitance: 150µF ~ 270µF
  • Lifetime: 2.000h at 105°C, rated voltage and ripple current
  • Dimension: 13,5x46x38,1mm ~ 13,5x46x57,2mm
  • Vibration proof up to 20g
  • AEC-Q200 qualified

Your Contact Person

For more information, please contact Roland Trimmel.

Roland Trimmel Product Manager +43 186 305-144 E-MAIL