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© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 • 864-963-6300 • www.kemet.com

A4031_ALS30_31 • 8/30/2016

Screw Terminal Aluminum Electrolytic Capacitors – ALS30/31 Series, +85°C

Mechanical Data

Polarity and Reversed Voltage

Aluminium Electrolytic capacitors manufactured for use in DC applications contain an anode foil and a cathode foil. As such,

they are polarized devices and must be connected with the +ve to the anode foil and the -ve to the cathode foil. If this were

to be reversed then the electrolytic process that took place in forming the oxide layer on the anode would be recreated in

trying to form an oxide layer on the cathode. In forming the cathode foil in this way, heat would be generated and gas given

off within the capacitor, usually leading to catastrophic failure.

The cathode foil already possesses a thin stabilized oxide layer. This thin oxide layer is equivalent to a forming voltage

of approximately 2 V. As a result, the capacitor can withstand a voltage reversal of up to 2 V for short periods. Above this

voltage, the formation process will commence. Aluminium Electrolytic capacitors can also be manufactured for use in

intermittent AC applications by using two anode foils in place of one anode and one cathode.

Mounting Position

The capacitor can be mounted in any position as long as the safety vent can operate. It is possible for some electrolyte to be

expelled. As this is a conducting liquid, suitable precautions should be initiated by the system designer to avoid secondary

short circuits.

The capacitors are designed to be mounted in free air and are not suitable for submersion in liquid.

Low Inductance Version

A low inductance version of the ALS30/31 capacitors can be designed upon request, typically reducing the inductance by up

to 40% of the standard capacitor's inductance. It is available in 77 & 90 mm diameters.

Insulating Resistance

≥ 100 MΩ at 100 VDC across insulating sleeve. UL recognized sleeving is available for custom parts in this range, upon

request.

(UL No. E358957)

Voltage Proof

≥ 2,500 VDC across insulating sleeve

Safety Vent

A safety vent for overpressure is featured on terminal deck. This is in the form of a rubber plug designed to relieve build-up

of internal pressure due to overstress or catastrophic failure.