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Three common faults of static phase shifters and their solutions. Static phase shifters are primarily used as industrial compensation devices for large and medium-sized high- and low-voltage wound-rotor asynchronous motors in industries such as cement, chemicals, mining, metallurgy, steel, papermaking, and pharmaceuticals. The three most common faults of static phase shifters are as follows: 1. Throttling of the thyristors can lead to the following consequences: when the static phase shifter is activated, the low-voltage air circuit breaker used for protecting the primary winding of the phase-shifting transformer may trip due to overcurrent, or fuses may blow. Alternatively, although the static phase shifter can be activated, the current of the main motor decreases less than normal and there is greater current fluctuation; the analog power factor meter gives unstable readings with large fluctuations in its pointer. Within a short time, the main circuit and reactors of the static phase shifter become severely overheated. The main reasons for this are: a) quality issues with the thyristor itself. A thyristor has a PNPN four-layer semiconductor structure and three terminals: the anode, the cathode, and the gate. Solution: Using high-quality thyristors is key to ensuring proper operation of the static phase-shifter. b Improper use and application details of thyristors: As a type of power semiconductor device, proper heat dissipation during its use is crucial, and it is also an important factor affecting its service life. Treatment: It is recommended to use air-cooled radiators. Additionally, the work surface of the countertop plays an important role in terms of electrical and thermal conductivity; it should be kept clean and flat, and the use of oxidizing agents, thermal conductive greases, vaseline, and similar substances should be avoided. Defects in the circuit design of the static phase-shifter itself, or improper operation of it: Some manufacturers of static phase-shifters, due to a lack of understanding of the actual operating conditions in which such devices are used, simply use the closing signal of the contactor that short-circuits the rotor circuit during the start-up of a wound-rotor motor as a condition for enabling operation of the phase-shifter. This approach is inappropriate and inaccurate. Handling: When an asynchronous motor starts, two types of torque act on the motor shaft. One is the electromagnetic torque generated by the motor itself, while the other is the load torque exerted by the machinery it drives on the shaft, along with counter-torques resulting from wind resistance and friction. The interaction between these two torques reflects the actual starting conditions of the motor. Moreover, both torques change throughout the starting process, which is what contributes to the complexity of asynchronous motor starting. The magnitude and variation of the current during startup are influenced and constrained by various factors. In wound-rotor asynchronous motors in use in industrial settings, when the short-circuit contactors in their starters close in order to short-circuit the rotor circuit, the motor has not yet reached its rated operating speed; it is still in the acceleration phase of starting. At this time, if a static phase shifter is connected or disconnected, the current in the asynchronous motor has not yet dropped to its stable operating level, which can cause excessive stress on the thyristors in the static phase shifter, potentially leading to their breakdown and damage! Therefore, strict quality control is applied to the quality of spare parts; reputable manufacturers are chosen for products such as thyristor devices and cooling fans, and careful attention is paid to details when replacing them, following the instructions provided in the product manuals. 2. Failure of the cooling fans can lead to deteriorated cooling conditions for the thyristors in the static phase shifter as well as for the key components located in the radiator compartment. This results in excessive heating of the thyristors and radiators, accelerating their oxidation and aging process and thus **reducing their normal service life. The main reasons for this are as follows: The cooling fan is an important auxiliary device equipped in static phase shifters to improve the operating conditions of thyristor devices; high quality standards must be applied to it. It cannot be considered merely an auxiliary device, and its temporary failure should not affect the operation of the static phase shifter! In fact, the operating conditions for thyristor devices are quite strict and demanding. If the cooling fan fails to function properly, it will lead to a severe deterioration of the cooling conditions for these devices, which will inevitably **reduce their operational efficiency and service life. Common faults of cooling fans include motor burnout and stopped fan blades; the main causes are manufacturing defects, dust entering the bearings, and inadequate routine maintenance. Treatment: Routine maintenance, improvement of on-site cooling conditions, as well as timely inspection and replacement of cooling fans. 3. Failures in the main control board, trigger board, etc., can lead to the following consequences: it may prevent the static phase shifter from being activated properly, or if it is activated, the current in the main motor will decrease less than normal and there will be greater fluctuations in this current. The analog power factor meter will show unstable readings with large swings in its pointer, and severe circulating current phenomena will occur in the main circuit of the phase shifter. To address this issue, the control circuit of the static phase shifter was modified; instead of using the signal indicating the closing of the contactor that short-circuits the rotor circuit during the start-up of a wound-rotor motor as the condition for activating the phase shifter, a time delay and current monitoring mechanism were added. Only after the motor has actually started up and its current is back to normal is it permissible to activate the phase shifter. Replacing all static phase shifters of the shunt sampler type with those based on Hall sensors and a nine-point intelligent algorithm can improve sampling accuracy and the effectiveness of reactive power compensation. Xiangyang Yuanchuang Industrial Control Co., Ltd. has been engaged in the production of industrial electrical equipment for over a decade. The company manufactures high-voltage switchgear, motor starters, high and low voltage water resistance cabinets, reactive power compensation cabinets, capacitor banks, static phase shifters, and many other types of products. These products are available at competitive prices, and many customers order customized versions of them according to their specific requirements.