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In electrical control systems, AC contactors are among the commonly used electrical components, and they are also a common source of various electrical faults. After long-term use—especially in harsh environments with high levels of dust—AC contactors may sometimes emit squeaking or rattling noises after being pulled in and held. The causes of this phenomenon are analyzed as follows.Squeaking Noise After Pull-In and HoldingA fully functional AC contactor makes no noise when energized and pulled

1. Fault Phenomena, Cause Analysis and Handling MethodsContactor does not operate or operates abnormally after coil energization Open circuit in coil control circuit; Check if there is wire breakage or loosening at the terminal blocks. If there is a wire breakage, replace the corresponding wire; if there is loosening, fasten the corresponding terminal block. Coil damage; Measure the coil resistance with a multimeter. If the resistance is ∞, replace the coil. Thermal relay not reset after operati

1 Analysis of Key Components of AC ContactorsAn AC contactor is an automated electromagnetic switch used for long-term, high-frequency switching of AC main circuits and control circuits. It features advantages such as automatic operation, under-voltage and no-voltage protection, high-capacity operation, strong stability, and low maintenance requirements. In the electrical control circuits of machine tools, AC contactors are mainly used to control electric motors and other loads.The key component

During operation, AC vacuum contactors are often subjected to various overvoltages such as lightning overvoltage and switching overvoltage. Therefore, AC vacuum contactors must have a certain voltage withstand capacity.An AC vacuum contactor is composed of a vacuum interrupter (its structure is shown in Figure 1), a housing, an electromagnetic system, a secondary circuit, and other components. Among these, the vacuum interrupter is the "heart" of the AC vacuum contactor, and its performance dire

In the high-voltage auxiliary power system of power generation enterprises, high-voltage vacuum contactors are used as control electrical appliances for high-voltage motors, transformers, frequency converters, and other electrical equipment. They enable remote control and frequent operation, thus gaining widespread application. If faults of vacuum contactors are not handled promptly, it will directly affect the safe and economical operation of the generating units in power generation enterprises

1. Applications of Low-Voltage Vacuum ContactorsLow-voltage vacuum contactors are suitable for power systems with an AC frequency of 50Hz and a rated operating voltage of 1140V, 660V, 500V, or 380V in the main circuit. They are used for remotely and frequently connecting and disconnecting circuits, as well as controlling three-phase AC motors or other electrical equipment. They are particularly applicable to locations with heavy loads and frequent operations.2. Structure of Low-Voltage Vacuum Co

I. Introduction to Cable Grounding Loop CurrentCables rated 110 kV and above use a single-core structure. The alternating magnetic field generated by the operating current induces a voltage on the metallic sheath. If the sheath forms a closed circuit through the earth, a grounding loop current will flow on the metallic sheath. Excessive grounding loop current (loop current exceeding 50 A, more than 20% of the load current, or a ratio of maximum-to-minimum phase current greater than 3) not only a

I. Functions of Metallic Sheaths and Necessity of RepairThe metallic sheath of high-voltage cables is a metal shielding structure laid outside the insulation layer, including types such as lead sheaths, aluminum sheaths, and steel wire armor. Its core functions include mechanical protection (resisting external impact and compression), electrochemical corrosion protection (isolating moisture and soil pollutants), electromagnetic shielding (reducing electromagnetic interference to the environment)

The arc extinguishing system of a DC circuit breaker is crucial for the safe operation of equipment, as the arc generated during current interruption can damage contacts and compromise insulation.In AC systems, the current naturally passes through zero twice per cycle, and AC circuit breakers take full advantage of these zero-crossing points to extinguish the arc.However, DC systems lack natural current zero crossings, making arc extinction significantly more difficult for DC circuit breakers. T

With the continuous development of smart grids, smart electricity meters are being increasingly widely applied, and various types of operational faults in smart meters are frequently encountered in energy measurement work. This paper analyzes the causes of smart meter failures and proposes corresponding solutions, using several actual operational fault cases as examples.1. Black ScreenA black screen refers to a powered meter with no display, which is the most commonly occurring fault in field-op