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Reverse Capacitor Tester

IP.com Disclosure Number: IPCOM000046369D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 62K

Publishing Venue

IBM

Related People

Roop, DS: AUTHOR [+2]

Abstract

The tester is designed to determine if the large electrolytic capacitors used in ferroresonant-type power supplies are installed with the correct polarity. These capacitors (from 10K to 450K microfarad in value) have no mechanical polarization to prevent assembly errors and, once installed, it is difficult or impossible to visually verify if orientation is correct.

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Reverse Capacitor Tester

The tester is designed to determine if the large electrolytic capacitors used in ferroresonant-type power supplies are installed with the correct polarity. These capacitors (from 10K to 450K microfarad in value) have no mechanical polarization to prevent assembly errors and, once installed, it is difficult or impossible to visually verify if orientation is correct.

Incorrect polarity will eventually cause the capacitor to breakdown. However, full breakdown may take from several minutes to several weeks to occur, and, until then, the power supply may function quite normally.

The tester is designed to allow manufacturing personnel to detect reverse polarity and thus prevent such failures in a customer installation. The detection is performed immediately after the testing of the power supply using the same connection to avoid extra load and unload time.

As shown in the circuit diagram of Fig. 1, voltage is applied to the capacitor under test (UUT) through relay Kl when the start button is pressed. The voltage is full-wave rectified, but not filtered, and has a peak value which is slightly under the maximum rating of the UUT. The power supply, in which the UUT is installed, is not powered on for this test. The duration of this voltage is typically 12 seconds, but can be adjusted for up to 30 seconds if a longer time is required to allow certain capacitor types to charge up and start to break down if installed with reverse polarity.

A voltage comparator monitors the current to the UUT through a one-ohm series resistor. The trip level is set slightly higher than the measured value of a known good capacitor and bleeder resistor. When the capacitor is installed with reversed polarity under the conditions described, the current required to keep the capacitor charged up is considerably greater than if it were installed correc...