1. In the course of use, the universal circuit breaker sometimes has a failure that the main contact does not close or disconnects itself during the closing period, which has serious consequences for production. After inspection, the cause of the failure was as follows:
(1) Since the release coil often passes a large current, the enameled wire is aged, the inter-turn short circuit, and the coil is overheated, causing unstable operation.
(2) Due to long-term use, the shunt spring is deformed and the pulling force is reduced, so that the shunt contact cannot be returned to the original position, causing the next time the universal circuit breaker cannot be sucked.
(3) Since the relay is under high voltage for a long time, the surface of the contact is oxidized, the contact resistance becomes large, and the contact cannot be normally turned on.
(4) Because the stator and rotor in the motor are misaligned and rubbed against each other, a large amount of heat is generated, causing the motor speed to be unstable or even stalled, causing the universal circuit breaker to fail to work normally.
In order to solve the problem of premature aging of the release coil, the following improvements were made: the original 0.31mm enameled wire was replaced by 0.29mm, the number of turns was unchanged, still 2130 rounds, and the resistance of the coil was increased from 81Ω to 86Ω. The current dropped from 4.7A to 4.4A, but after a trial run for a while, the coil was hot. The enameled wire was replaced by 0.19mm, the number of turns was unchanged, it was still 2130 rounds, and the resistance of the coil was increased to 132Ω. The current drops to 2.9A, but the electromagnet does not pick up; if it is 0.25mm, the number of turns is unchanged, it is still 2130 rounds, the resistance of the coil is increased to 100Ω, the current passed drops to 3.8A, the coil is not hot, and It also meets the requirements for attracting electromagnets. After a period of use, no abnormalities occurred.
After the shunt spring was deformed, the tensile tester was tested to have a tensile force of 100 g. After many experiments, the author measured that the tension of 220 grams just satisfies the requirement that the shunt coil can be normally sucked and the shunt contact can be reset. After replacing with a new shunt spring with a pull force of 220 grams, the universal circuit breaker works fine.
After the relay contacts are oxidized, the relay cover can be removed and each contact lit with sandpaper. After the reinstallation, the universal circuit breaker works stably.
If a fault occurs, the motor must be removed and the motor cover opened to check. The rotor bearing is tilted and the rotor and stator are rubbed. Move the bearing positively, fix it, close the cover, test run, everything is normal.
Second, the main measures for the maintenance of universal circuit breakers are:
In order to prevent (prevent, avoid) all measures taken to cause injury to personnel in the vicinity of the switch when a faulty arc is generated in the switchgear, personal measures are taken. A typical example is to install a pressure relief device on the top of the cabinet. The pressure generated when the fault arc ignite forces the pressure relief device to open and discharges harmful hot gases to the top of the cabinet to protect the surrounding personnel.
Limiting the intensity of the fault arc and limiting the fault arc can reduce the degree of disaster. The size of the fault arc is mainly determined by the short-circuit capacity. This can be considered to reduce the strength of the short-circuit current in the design of the power supply system, and the current-limiting circuit breaker is selected.
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