Product reliability is a crucial aspect of its quality attributes. Higher reliability means lower maintenance costs, minimizing user expenses and ensuring the normal operation of equipment. Furthermore, only highly reliable products can truly compete in the market. I. Current Status of Reliability in Contactless Voltage Regulators In the modern power supply field, ensuring precise control and reliable operation of power devices necessitates the use of power electronics technology and power semiconductor devices (thyristors). Power semiconductor devices offer numerous advantages, including high efficiency, excellent control performance, small size, light weight, and high reliability. Therefore, upgrading power voltage regulators using power electronics technology has become a major development direction for high-power power voltage regulators. Since 1999, Shanghai Panden New Power Supply Co., Ltd., responding to market demand for a new generation of high-power voltage regulators, has invested heavily in research and development. Combining its over ten years of experience in power voltage regulator production, the company upgraded traditional high-power compensated power voltage regulators, successfully developing the DBW5/SBW5 series of high-power contactless compensated power voltage regulators. This pioneering work filled a market gap and earned patent authorization from the State Intellectual Property Office. Panden is also the only voltage regulator company recognized by Shanghai Municipality as a high-tech achievement transformation enterprise. Confirmed by the Technical Documentation and Information Center of the Chinese Academy of Sciences, the "Pandeng" contactless voltage regulator features several domestic and international firsts, achieving an overall technological level comparable to international products. This product features no mechanical operation, no carbon brush contact, no noise voltage regulation, no instantaneous power outages, full three-phase regulation, extremely fast response speed, lightning surge protection, and all protection functions. Its stable and reliable operation enables long-term maintenance-free operation. With a capacity of up to 2000KVA and a compensation range of ±50%, this new generation of green, environmentally friendly, and energy-saving product boasts high efficiency and reliable operation. Inspected by the Product Quality Supervision and Inspection Center of the Ministry of Information Industry, it has been recognized as the most advanced and largest-capacity contactless voltage regulator currently available in China. As contactless voltage regulators have gained market and user acceptance, numerous manufacturers have subsequently launched contactless voltage regulators with varying structures. Due to differences in main circuit structures, their performance often varies significantly. Furthermore, some manufacturers have not invested enough in technology or conducted in-depth research; they lack sufficient testing and understanding of the performance and application of the key component—the thyristor module; and a few even engage in cost-cutting practices, using old or inferior components. All these factors ultimately affect product reliability, resulting in highly unstable performance and poor reliability in many manufacturers' contactless voltage regulators. Over time, this has led many users to mistakenly believe that all contactless voltage regulators on the market are unreliable and unusable, causing them to hesitate to purchase them. II. Comparison of "Pandeng" Contactless Voltage Regulators with Other Contactless Voltage Regulators To clarify some misunderstandings among users, we will analyze the contactless voltage regulators on the market. The main difference between contactless voltage regulators with different main circuit structures lies in the method of adjusting the compensation voltage, which directly affects the regulator's reliability, dynamic response, voltage regulation accuracy, voltage regulation range, maximum capacity, waveform distortion, and other performance indicators. Currently, the main circuits of contactless voltage regulators on the market can be roughly divided into the following three types: 1. Autotransformer Voltage Regulating Compensation Type (Patented Technology of Shanghai Pandeng New Power Supply Co., Ltd.) This structure controls the on/off state of the bidirectional thyristor to switch the taps of the autotransformer, thereby changing the magnitude and polarity of the compensation voltage of the compensation transformer to achieve a stable output voltage. Main advantages (1) Due to the use of autotransformer tap-level voltage regulation, the switching voltage of the bidirectional thyristor is reduced (from 220V to below 200V), and the surge current generated during switching is suppressed (the autotransformer itself is a high-power reactor), thus greatly improving the working reliability of the bidirectional thyristor. (2) Due to the use of "interlock isolation" technology (patent technology of Shanghai Pandeng New Power Company) in the control circuit, the circulating current problem caused by external interference causing the bidirectional thyristor to malfunction is completely solved, effectively avoiding damage to the thyristor device. (3) Due to the use of analog integrated circuits in the control part, it has a strong adaptability to harsh power grid environments. 2. Autotransformer This type of contactless voltage regulator directly changes the turns ratio of the autotransformer by controlling the switching of the bidirectional thyristor, thereby achieving the purpose of stabilizing the output voltage. The main disadvantage is that because the thyristor is directly connected in series in the main circuit, the entire load current flows through the thyristor. Transient currents and fluctuations in the load current can easily damage the thyristor. Furthermore, the large amount of heat generated by the long-term flow of high current also puts the thyristor under harsh operating conditions, leading to performance degradation and decreased reliability. Additionally, using this structure for a large-capacity voltage regulator requires a very large thyristor capacity, which poses significant challenges in determining the thyristor's margin factor and designing its heat dissipation, easily causing reliability degradation. Compared to autotransformers, the advantages of the "Pandon" contactless voltage regulator are: Because the thyristor in the "Pandon" contactless voltage regulator is not in the main path of the load current, but only connected in the voltage regulation circuit, the current flowing through it is small, only a fraction of the load current, or even a dozen or twenty-something percent. Therefore, the device's margin factor can be selected more freely, and the heat generated during operation is not significant, allowing the thyristor to operate reliably for a long time. At the same time, the voltage regulator capacity can be made very large (the largest capacity currently produced is 2000KVA). 3. Pure Compensation Type: This structure uses the switching of bidirectional thyristors to control the connection, disconnection, or polarity change of the compensation transformer combination, thereby achieving a stable output voltage. The main disadvantage is that the thyristor is directly connected between the phase line and the neutral line (220V) via a bridge arm, resulting in a high operating voltage and large inrush current during switching, which easily damages the thyristor. Furthermore, this circuit is prone to short circuits between the phase line and the neutral line when the thyristor is mis-connected, instantly burning out the thyristor, thus its reliability is very poor. In contrast to the pure compensation type, the advantages of the "Pandon" contactless voltage regulator are: Because the thyristor network in the "Pandon" contactless voltage regulator is located on the output side of the compensation transformer and further stepped down by an autotransformer, the switching voltage of the thyristor is reduced (from 220V to 200V or lower), and the inrush current during switching is suppressed (the autotransformer itself is a high-power reactor), thus greatly improving the reliability and anti-interference capability of the thyristor. III. Measures Taken by Panden Contactless Voltage Regulator to Enhance Reliability To ensure high product reliability, Shanghai Panden New Power Supply Co., Ltd. has adopted a complete set of scientific methods. The following is an introduction to the measures we have taken in several key aspects, including "reliability design", "reliability growth", and "reliability management". 1. Reliability Design Measures (1) Derating Design To reduce the failure rate and improve product reliability, we have adopted the "derating design" method in a targeted manner in the selection of parameters of major components. For example, for the capacity of the thyristor module, we have selected it according to 3 to 5 times the on-state average current ITAV, which is equivalent to doubling the design margin coefficient used in normal operation. This strengthens the key links affecting the reliability of the contactless voltage regulator and greatly improves the reliability of the product. (2) Electromagnetic Compatibility Design To prevent errors or failures caused by the electromagnetic environment at the voltage regulator's working site, we have taken many measures to eliminate and reduce interference. For example, we use the most advanced MOV matrix technology from JOSLYN Corporation in the world to effectively suppress surge spikes generated during the operation of the thyristor (our company is the general agent in China for surge protection products from JOSLYN Corporation in the United States). In addition, we have strengthened the power supply filtering design to improve the anti-interference capability of the system. (3) Heat dissipation design In terms of heat dissipation design, after several years of exploration and improvement, we have designed a set of reasonable heat dissipation measures and applicable heat dissipation data, which effectively reduces the temperature rise of the thyristor device and the chassis, and greatly reduces the performance degradation and failure of the thyristor device caused by overheating. 2. Reliability improvement measures For contactless voltage regulators, we attach great importance to continuously correcting defects in product design and manufacturing, and continuously improving product reliability. Since the first product was manufactured in 1999, we have continuously tracked the user's usage, combined with the feedback information from after-sales service, continuously analyzed and studied the sources of failure and potential fault hazards, made timely improvements, and ensured that no new fault sources are introduced when revising the design. In the product design and revising design stages, we have conducted a large number of tests and have always insisted on using the test method to check the fault sources, striving to solve the fault hazards in the product design stage. 3. Reliability Management Measures Shanghai Panden New Power Supply Co., Ltd. strictly adheres to the ISO9000 international quality certification system for product quality management. A complete system for collecting, processing, reporting, analyzing, and handling faults and defects occurring during product manufacturing and use has been established, providing a strong guarantee for improving product reliability. Furthermore, we have implemented strict quality control in the selection of key components such as thyristors and transformers. For example, for thyristor modules, we have strengthened the screening of on-state peak voltage (VTM) to keep device temperature rise within a low range; we have also set higher requirements for the thyristor gate process. For the main and auxiliary transformers, we have adopted a toroidal transformer structure with low loss, low temperature rise, and high efficiency. Through several years of effort, the reliability of "Pandeng" contactless voltage regulators has been continuously improved; to date, the average mean time between failures (MTBF) of the products has reached 100,000 hours. IV. About Microcontroller-Controlled Contactless Voltage Regulators Currently, many contactless voltage regulators on the market use microcontrollers to build their control systems. While microcontroller technology offers numerous advantages and is relatively advanced, it also has weaknesses, namely, the complexity and difficulty of handling interference. For high-power voltage regulators, the operating environment, especially the electromagnetic environment, is often harsh. Therefore, the circuit structure and control system should strive for simplicity and reliability, with strong anti-interference capabilities to ensure high operational reliability. Blindly applying microcontroller technology indiscriminately in pursuit of trendiness will be counterproductive. Therefore, we believe that unless there are significant improvements in the main performance indicators of the voltage regulator, the application of microcontroller technology in contactless voltage regulators should be approached with caution. V. Overview In the past, most voltage regulators on the market were mechanical carbon brush type. However, using carbon brushes and mechanical transmission inevitably leads to many disadvantages and problems, such as short service life, slow response speed, small carbon brush contact surface affecting output current, and rapid carbon brush wear requiring frequent maintenance and replacement. Therefore, contactless voltage regulators have become the inevitable choice for most users. With continuous improvements in technology and processes by manufacturers, the reliability of contactless voltage regulators is constantly increasing. Simultaneously, as users gain a deeper understanding of the product, contactless voltage regulators are poised for a brighter market future. Shanghai Panden New Power Supply Co., Ltd.'s "Pandeng" contactless voltage regulators are now widely used in various industries, including broadcasting, telecommunications, power, petrochemicals, CNC machine tools, printing equipment, various manufacturing equipment, and medical equipment. Especially in high-capacity contactless voltage regulators, we are far ahead of our competitors. In 2002, we were the first in China to manufacture a 1200KVA contactless voltage regulator, which passed the inspection of the Ministry of Information Industry and was successfully applied in the telecommunications industry. In recent years, we have successively produced 1400KVA, 1600KVA, and 2000KVA contactless voltage regulators, which have been successfully applied in the power, printing, and tobacco industries. This series of "firsts" in China remains unbroken to this day! We can proudly say: our patented products have been imitated, but our contactless technology has never been surpassed! Currently, "Pandeng" contactless voltage regulators have been exported to Turkey, India, North Korea, and Southeast Asian countries, establishing a good reputation among users at home and abroad. Their high reliability has also won unanimous praise!