Aluminum electrolytics come in a variety of sizes and terminations, but one thing most of them have in common is their cylindrical shape.  This shape limits the CV possible when low profile electronic components are a requirement without utilizing multiple capacitors.

The ALR81 and ALR91 series are KEMET’s first introduction of “Aluminum Rectangular” products which are Aluminum Electrolytics in the shape of a rectangular prism. The rectangular shape offers big advantages in energy density, low profile, and ease of use in banks.

These series are being released for the EMEA and Asian markets.

How low can you go?

With a maximum height of 13.3mm, these capacitors can often replace 3 or more radials and 6 or more V-chips.  This allows engineers to meet difficult height restrictions without sacrificing CV or relying on multiple capacitors in series or parallel connections.

When using multiple capacitors, the dimensional outline of the bank equates to the total footprint of the solution. In addition to the components themselves, the empty space in-between the capacitors adds to the footprint. Therefore, the energy density of a bank will always be lower than that provided by one capacitor of the same dielectric.  From a reliability standpoint, fewer components reduces risk of a failure.

What’s in it for me?

These capacitors are packed.  Both series are rated to 5,000 hours.

Thotspot Votlage Range Capacitace Range
ALR81 -55ºC to 105ºC 24 – 275 VDC 140 – 17,000 µF
ALR91 -55ºC to 125ºC 20 – 250 VDC 140 – 17,000 µF

I’m pickin’ up good vibrations

Parts in these series are rated as high as 30-80g by size. This level of vibration far exceeds most other aluminum electrolytic capacitors on the market.

  • MIL-STD-202, Meth. 204, Sine Swept, IEC 60068-2-6
  • Vibration applied in three directions 4-hour sessions at 10 – 2,000 Hz
  • Capacitor clamped by body

The clamping requirement is common for all aluminum electrolytics in applications with high vibration. The rating is the ability of the element inside the case to withstand vibration rather than the strength of the terminals themselves. Clamping the capacitor protects the terminals/leads from being broken and losing electrical contact.

As long as the capacitors are sufficiently clamped to protect the leads from breaking, the capacitors can be mounted in any direction.

Benefits Galore – we need more!

Take it up high!

ALR81 and ALR91 are rated for use up to 80,000 feet or 24,400 meters.

Take it down low!

These capacitors have great cold temperature capability. The typical curves show more than 90% of the capacitance is retained at –55°C and the standard test frequency of 120 Hz.

ESR increases from 0.033 Ω at 25°C to only 0.47 Ω at –55°C.  Almost no change between 0ºC and 125ºC.

Weight may be less than the alternative of multiple capacitors – critical for many military and aerospace applications.

Stack Attack!

Because of the shape, using multiple capacitors in a module or bank is simplified.  A cooling system for thermal management can use the prismatic shape to its advantage due to low thermal resistance.  Note that using multiple capacitors stacked together will change the thermal dynamics and therefore the ripple current capability versus a single capacitor.  Contact KEMET sales for assistance in this case.

In Summary

This product meets needs not addressed by other aluminum electrolytic types in terms of vibration, low profile + footprint for a given CV & ripple current, low temperature range performance, and high-altitude use.

So, when you need an aluminum electrolytic capacitor, but a cylindrical shape is just another can, think KEMET’s Aluminum Rectangular or ALR series for your applications with these needs:

  • Reduced size
  • Reduced weight
  • Extremely long life
  • High Altitudes (24,400 meters)
  • Use in extreme low temperature environments
  • Severe vibration requirements (up to 80g)

And stay tuned for the AAR series or Aluminum Automotive Rectangular families from KEMET which will be available globally for all AEC-Q200 automotive applications.