SU1071970A1 - Break-out contact pair quality determination method - Google Patents

Description

(Ls

CO-4

The invention relates to electrical engineering, in particular to methods of testing and testing electromagnetic relays, contactors and other discontinuous switching devices, and can be used to diagnose contact conditions and to detect defects.

A known method for determining the contact resistance of a contact pair is that the contact resistance is determined on the basis of a voltage measurement on the test contacts when an electric current is passed through them of a nominal or close SP value.

However, this method cannot be applied to diagnose the state of contact pairs, as when current passes through the contact pair. breakdown of contact insulation films (fritting) may occur. As a result, the presence of a stable electrical contact is detected while its actual state may be close to destruction.

The closest to the invention in technical essence and the achieved result is a method, which is judged on the quality of contacts, transition resistance, by distorting the front of the top and falling off of a rectangular pulse of nanosecond duration when switching a signal transmitted through a contact pair and formed by a special wideband impulse circuit C L1.

However, the known method cannot be used to determine the quality of discontinuous contacts in the millisecond range, in the contact range of electromagnetic relays, in low-current collector devices with sliding contacts (otherwise the device forming a rectangular pulse must have a cable with a length of 100 - 300 m), Reliability measurements of the contact resistance and their quality are low in view of the fact that the operating conditions of the contact pair in the monitoring process differ from the conditions of normal operation. In the normal mode, nominal currents flow through closed contacts for a long time, generating a certain amount of Joule heat and heating the contact surfaces up to 1200 ° C. Nanosecond pulses transmitted through contacts do not create conditions equivalent to the real case. Therefore, the physicochemical processes that take place on the contacting surfaces and determine the quality of the contact will be significantly different from each other.

If a rectangular pulse of a millisecond duration with a corresponding power is passed through the contact pair, the advantage of the known method will be eliminated, since simultaneously with the expansion of the impulse, the influence of contact quality on the distortion of the front, peak, impulse decay will drop, and will not exist at all due to the fact that the intensity of the high-frequency components of the square-wave signal, which is primarily affected by the contact state, decreases with increasing duration spine impulse. Consequently, a different, fundamentally new way of determining the quality of contacts is needed.

The aim of the invention is to improve the reliability of determining the quality of contacts and the detection of their defect.

The goal is achieved by the method of determining the quality of a contact pair of discontinuous type, consisting in measuring distortions when a signal is switched, using an electromagnetic broadband pulse of a spark gap of contacts when they break, determine the shape of its energy spectrum and fade it with the form of the energy spectrum of the reference contact couples.

Measurements are made under the same conditions for the same type of test and reference switching devices.

In contrast to the known method, the switching device operates in its normal mode and, therefore, the actual quality of the contacts is fixed, including the presence of fritting. There is no need to obtain a rectangular impulse of a potential signal with the help of special equipment. Diagnostics of the contact pair was fully disassembled, disconnected from relays, contactors, etc.

To implement the method, in a controlled contact pair, a broadband amplifier is connected either directly or through an inductive coil, magnetically coupled to a spark gap of contacts. The output of the wideband amplifier is connected to a spectrum analysis, with which the shape of the energy spectrum of the signal is determined.

The result obtained is compared with the shape of the energy spectrum.

Removed from the contact pair of the reference switching device.

The shape of the energy spectrum of a high-frequency signal formed by a spark gap when the contacts are broken; depends on the state of contact surfaces: on the thickness of the insulation film, the presence of fritting, soiling, burning, etc.

Each listed state of the contact pair corresponds to a certain form of the energy spectrum of the signal. I The proposed method therefore makes it possible to reliably, with a high degree of confidence, diagnose the state of the contact and reveal their defects.

The advantage of the proposed method is its economic efficiency, since there is no need for a device to form a rectangular potential impulse.

Claims (1)

METHOD FOR DETERMINING THE QUALITY OF A CONTACT PAIR OF A DISCONNECT TYPE, consisting in measuring distortions during signal switching, characterized in that, in order to increase the reliability of determining the quality of contacts and identifying their defect, they use a broadband pulse of the spark gap when they break, determine the shape of its energy spectrum and compare it with the shape of the energy spectrum of the reference contact pair.