DD242302A1 - PROCESS FOR REFORMATING ELECTROLYTE CAPACITORS - Google Patents

Abstract

The invention relates to a method for reformulating bipolar electrolytic capacitors after the manufacturing process. It is an object of the invention to minimize by a suitable Nachformierverfahren the damage of the oxide layer by incorrect polarity, to obtain two uniformly well-formed anode foils. This is achieved by subjecting pre-assembled capacitors whose coils have not yet been reformed to 50 Hz alternating current treatment. Due to the high power loss, the duty cycle is chosen very short and pauses between the switch-on phases so long that the capacitor is not heated up and destroyed by the power loss inadmissible.

Description

'Field of the invention

The invention relates to a method for reforming bipolar electrolytic capacitors after the manufacturing process, before they are subjected to the final test.

Characteristic of the known technical solutions

For the production of electrolytic capacitors, aluminum foils coated with a dielectrically active oxide layer are used, in short called anode foils. The aluminum oxide layer is applied to the aluminum foils in a continuous process by the so-called deformation process. The quality of this oxide layer (dielectric) determines the quality of the capacitor. During the subsequent production process, the formed anode foils are cut to the appropriate bandwidths, resulting in cut edges that have no oxide layer. By rewinding and producing the capacitor winding, the very sensitive, brittle and only max. 0.7 μm thick oxide layer damaged.

For these reasons, it is imperative, after the impregnation of the coil or after completion of the capacitor to subject this to a reforming to heal all defects of the oxide layer and to form the cut edges.

This process only takes place correctly if the anode foil is positively poled, since only in this polarity does the oxide layer in conjunction with the electrolyte act as a barrier layer and new oxide can form. In case of polarity reversal, the oxide layer is practically conductive and is degraded during continuous polarity reversal with higher voltage in their quality.

In polar electrolytic capacitors no problems arise in this regard, since in these a polarity reversal is not required

For bipolar electrolytic capacitors, both anode foils must be reformed. In the ready-mounted capacitor, a temporary polarity reversal of the two anodes is inevitably necessary.

In a known way, one can first transform the one and then the other anode foil, and in each case the total necessary time of z. For example 6 hours each. This method has the disadvantage that the last incorrectly poled anode loses quality very much ah, the residual current has increased significantly. An improvement brings already a different cycle, in which the two anodes are alternately nachformiert and each slide z. B. 3 times 2 hours of voltage and thus the wrong polarity is shorter. It is even better if the cycle times are shorter towards the end of the formation,

z. B. per anode 3.2 and 1 hour in alternation, so that the total time of 6 hours is maintained. But even with the last incorrectly poled anode damage remains, despite the long forming time of 2 times 6 hours.

Object of the invention

The aim of the invention is to minimize by a suitable Nachformierverfahren for bipolar capacitors, the damage of the oxide layer by false polarity to obtain two uniformly well-formed anode foils.

Explanation of the essence of the invention

The invention is based on the object, a bipolar electrolytic capacitor in the already assembled state, in which the access to a possibly lying between the two anode sheets neutral unformed film is not possible to reformate so that by the case inevitable false polarity of an anode whose oxide layer not harmed. Bipolar electrolytic capacitors, e.g. As engine starter capacitors are operated in the application with relatively high AC voltage in the range between 100 and 380V.

Due to the large loss factor of electrolytic capacitors, up to 10% of the AC power is converted into heat. For this reason, starting electrolytic capacitors are allowed only for duty cycle up to 3 seconds with a nominal playing time of 3 minutes. The duty cycle is between 0.55 and 1.7%. Based on this mode of operation, which demonstrably does not result in damage to the oxide layers, the problem of reforming has been solved as follows. Ready assembled capacitors that have not yet been reformed as a coil are subjected to 50 Hz alternating current treatment for reforming purposes. Due to the high power loss, the duty cycle is chosen to be very short and so long pauses between the power-up phases that the capacitor is not inadmissible heated by the power loss and destroyed. However, a certain degree of self-heating has a positive effect on the process. If you want to bypass the strong self-heating, so you choose an AC of low frequency or goes to a DC shaping, which is reversed at short intervals each, the capacitors are only unloaded and need no pause time. It has been found that with this method the post-forming voltages can be made smaller, e.g. only the nominal AC voltage instead of 1.4 times the same.

Another advantage of this method is the recognition that the overall reformation time, including break time in AC forming, can be reduced from 12 to 1-2 hours, the quality of the capacitors being better than the old method. By shortening the total time, it is possible for the first time to automatically reformulate the capacitors in a continuous process.

embodiment

The method according to the invention will be explained with reference to two exemplary embodiments.

Example 1 *

The fully assembled bipolar capacitors are transformed with the following parameters:

Reforming voltage: nominal AC voltage of the capacitor

Duty cycle: 3 s

Break time: 3 min

Total time: 2 h

Example 2

The capacitors are reformed with DC voltage, the polarity being changed as follows:

Next photo voltage: DC voltage equal to 1.2 times the rated AC voltage

Duty cycle: 2 min

Discharge resistance: 0.5 k

Pause time: none, immediately apply voltage of reversed polarity after discharge

Total time: 60 min

For gentler treatment, the stresses at the beginning of the formation may be adjusted to e.g. Reduced 80% and only after the half of the total forming time to the specified height regulated.

In both examples, one arrives at capacitors whose anode foils are uniformly replicated and result in extremely low residual currents. Also the other properties, e.g. Heat balance are positively influenced by the method according to the invention.

Claims (9)

-1- Z4Z3UZ Claim: 1. Method for reforming electrolytic capacitors, e.g. Motoranlaßelektrolytkondensatoren in which both anodes are formed successively, one of which is always exposed to a wrong polarity, characterized in that the reforming with AC voltage in intermittent operation or with DC voltage whose polarity changes in more or less long time intervals, is performed. 2. The method according to item 1, characterized in that the height of the AC voltage between 50 and 140% of the nominal AC voltage of the capacitor is and the frequency is selected in the range of 1 to 120 Hz, preferably the respective available network frequency. 3. The method according to item 1 and 2, characterized in that the formation takes place with AC voltage in intermittent operation, in particular with 0.2 to 3% relative duty cycle. 4. The method according to item 1,2 and 3, characterized in that the Gesamtformierdauer 0.25 to 6 hours, in particular 2 hours. 5. The method according to item 1, characterized in that the height of the DC voltage is between 70 and 150% of the nominal AC voltage, preferably equal to the nominal AC voltage. 6. The method according to item 1 and 5, characterized in that the capacitors are discharged before each polarity reversal. 7. The method according to item 1,5 and 6, characterized in that the turn-on of the DC voltage between 0.1 and 5min, preferably be 1 min. 8. The method according to item 1, 5,6 and 7, characterized in that the Gesamtformierzeit is between 0.25 and 4 hours, preferably only 1 hour. 9. The method according to item 1 to 8, characterized in that to maintain the changing Formierbedingungen the overall process is carried out in a Formierautomaten.