Talking about the reliability of contactless voltage stabilizer

The reliability index of a product is an extremely important part of its quality attributes. The higher the reliability of the product, the lower the cost of maintenance required, which can minimize the user's expenses and ensure the normal operation of the user's equipment. At the same time, only products with high reliability can be truly competitive in the market.

1. Current status of reliability of contactless voltage regulator products

In the field of modern power supply, to ensure that the power supply device can be precisely controlled and reliably operated, it is necessary to adopt power electronics technology and use power semiconductor devices (thyristors) in the device. Power semiconductor devices have many advantages such as high efficiency, good control performance, small size, light weight, and reliable use. Therefore, the use of power electronics technology to upgrade power regulators has become the main development direction of high-power power regulators .

Since 1999, Shanghai Pandenxin Power Supply Co., Ltd. has invested a lot of R&D funds and technical strength to meet the market demand for a new generation of high-power voltage stabilized power supplies. Combining its own more than ten years of experience in power voltage stabilizer production, it has upgraded and transformed traditional high-power compensated power voltage stabilizers and finally successfully developed the DBW5/SBW5 series of high-power contactless compensated power voltage stabilizers, which took the lead in filling the market gap and obtained patent authorization from the State Intellectual Property Office. At the same time, it is the only high-tech achievement transformation enterprise in the voltage stabilizer industry recognized by Shanghai.

Confirmed by the Technical Documentation and Information Center of the Chinese Academy of Sciences, many technologies of the "Pandeng" contactless voltage stabilizer are first-of-its-kind at home and abroad, and its overall technology has reached the advanced level of similar international products. The whole machine of this product has no mechanical operation, no carbon brush contact, no noise voltage regulation, no instantaneous power failure, and all three-phase regulation. It has an extremely fast response speed, lightning surge protection and all protection functions, and works stably and reliably, making the voltage stabilizer maintenance-free for a long time. The capacity has reached 2000KVA, the compensation range can reach ±50%, and it has high efficiency and reliable operation. It is a new generation of green, environmentally friendly and energy-saving products. After the inspection of the product quality supervision and inspection center of the Ministry of Information Industry, it was determined to be the most advanced and largest capacity contactless voltage stabilizer in China.

As contactless voltage stabilizers are gradually recognized by the market and users, many voltage stabilizer manufacturers have subsequently launched contactless voltage stabilizers with different structures. Due to the different main circuit structures, their performance differences are often quite large; in addition, some manufacturers have not invested enough in technology and have not conducted in-depth research; they also lack sufficient testing and understanding of the performance and application of the key components of contactless voltage stabilizers, the thyristor modules; even a few manufacturers have cut corners and used old components as new ones, or inferior components as good ones. All these reasons are finally reflected in the reliability of the products, causing the performance of many manufacturers' contactless voltage stabilizers to be extremely unstable and the reliability of use to be very poor. Over time, many users have formed a misunderstanding that the contactless voltage stabilizers on the market are unreliable and unusable, and finally dare not buy them.

2. Comparison between "Pandeng" contactless voltage stabilizer and other contactless voltage stabilizers

In order to clarify some misunderstandings among users, we will analyze the contactless voltage stabilizers on the market.

The main difference between contactless voltage stabilizers with different main circuit structures lies in the way the compensation voltage is adjusted, which is directly related to the performance indicators of the voltage stabilizer, such as working reliability, dynamic response, voltage regulation accuracy, voltage regulation range, maximum capacity, waveform distortion, etc.

The main circuits of the contactless voltage regulators currently on the market can be roughly divided into the following three types:

1. Auto-coupling voltage regulation compensation type (patented technology of Shanghai Pandengxin Power Supply Company)

This structure switches the tap of the autotransformer by controlling the on and off of the bidirectional thyristor, thereby changing the size and polarity of the compensation voltage of the compensation transformer to achieve the purpose of stabilizing the output voltage.

Key Benefits

(1) The use of autotransformer tap-type voltage regulation not only reduces the on-off voltage of the bidirectional thyristor (from 220V to below 200V), but also suppresses the surge current generated during gear shifting (the autotransformer itself is a high-power reactor), thereby greatly improving the working reliability of the bidirectional thyristor.

(2) The "interlock isolation" technology (patented technology of Shanghai Pandenxin Power Supply Co., Ltd.) is used in the control circuit to completely solve the circulation problem caused by the misoperation of the bidirectional thyristor due to external interference, and effectively avoid the damage of the thyristor device.

(3) Since the control part mainly uses analog integrated circuits, it has strong adaptability to harsh power grid environments.

2. Auto-coupling

The contactless voltage stabilizer of this structure directly changes the transformation ratio of the autotransformer by controlling the on and off of the bidirectional thyristor, thereby achieving the purpose of stabilizing the output voltage.

Main Disadvantages

Since the thyristor is directly connected in series in the main circuit, the entire load current flows through the thyristor. Transients and fluctuations in the load current can easily damage the thyristor. The long-term passage of large current generates a lot of heat, which also causes the thyristor to work under harsh conditions, resulting in performance degradation and poor reliability.

In addition, when using this structure to make a large-capacity voltage stabilizer, the thyristor capacity must also be large, which creates great difficulties in determining the thyristor margin coefficient and the thyristor heat dissipation design, and can easily cause reliability to deteriorate.

Compared with the auto-coupling type, the advantages of "Pandeng" contactless voltage stabilizer are:

Since the thyristor of the "Pandeng" contactless voltage stabilizer is not in the main path of the load current, but is only connected to the voltage regulation circuit, the current passing through is not large, only a few parts of the load current, or even a dozen parts or a twentieth part. Therefore, the margin coefficient of the device can be selected easily, and the heat is not severe during operation. The thyristor can work reliably for a long time. At the same time, the capacity of the voltage stabilizer can also be made very large (the maximum capacity that can be produced at present is 2000KVA).

3. Pure compensation type

This structure controls the input, output or polarity change of the compensation transformer combination through the on and off of the bidirectional thyristor, thereby achieving the purpose of stabilizing the output voltage.

Main Disadvantages

The thyristor is directly connected between the phase line and the neutral line (220V) in the form of a bridge arm, so the working voltage is high and the surge current generated when shifting gears is large, which can easily damage the thyristor. At the same time, when the thyristor is misconnected, this circuit can easily cause a short circuit between the phase line and the neutral line, instantly burning the thyristor, so its reliability is very poor.

Compared with the pure compensation type, the advantages of "Pandeng" contactless voltage stabilizer are:

Since the thyristor network of the "Pandeng" contactless voltage stabilizer is located on the output side of the compensation transformer and is stepped down by the autotransformer, the on-off voltage of the thyristor is reduced (from 220V to 200V or lower), and the surge current generated during gear shifting can be suppressed (the autotransformer itself is a high-power reactor), thereby greatly improving the working reliability and anti-interference ability of the thyristor.

3. Measures taken by "Pandeng" contactless voltage stabilizer to enhance reliability

In order to ensure the high reliability of its products, Shanghai Pandenxin Power Supply Co., Ltd. has adopted a complete set of scientific methods. The following only introduces the measures we have taken in several major aspects such as "reliability design", "reliability growth" and "reliability management".

1. Reliability design measures

(1) Derating design

In order to reduce the failure rate and improve product reliability, we have appropriately adopted the method of "derating design" in the selection of parameters of main components. For example, we have selected the capacity of thyristor modules according to 3 to 5 times the average on-state current I _TAV , which is equivalent to doubling the design margin coefficient that is usually used. This strengthens the key links that affect the reliability of contactless voltage regulators and greatly improves the reliability of products.

(2) Electromagnetic compatibility design

In order to prevent errors or failures caused by the electromagnetic environment at the work site of the voltage stabilizer, we have taken many measures to eliminate and reduce interference. For example, we use the world's most advanced MOV matrix technology from the American JOSLYN Company to effectively suppress the surge spikes generated during the operation of the thyristor (our company is the general agent of the surge protection products of the American JOSLYN Company in China). In addition, we have also strengthened the power supply filter design to improve the anti-interference ability 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 reduce the temperature rise of thyristor devices and chassis, and greatly reduce the performance degradation and failure of thyristor devices caused by overheating.

2. Reliability growth measures

For contactless voltage stabilizers, we attach great importance to continuously correcting defects in product design and manufacturing, and continuously improving product reliability. Since the first product was shipped in 1999, we have been tracking user usage, combining feedback from after-sales service, continuously analyzing and studying the source of failures and potential hidden dangers, making timely improvements, and ensuring that no new sources of failure are introduced when revising the design.

During the product design and revised design stages, we have conducted a large number of tests and have always insisted on using experimental methods to check the source of failures, striving to resolve potential failures during the product design stage.

3. Reliability management measures

Shanghai Pandenxin Power Supply Co., Ltd. strictly implements product quality management in accordance with the ISO9000 international quality certification system, and has established a complete set of collection, sorting, feedback, analysis and processing systems for failures and defects occurring during the production and use of products, providing a very strong institutional guarantee for improving product reliability.

In addition, we have also carried out strict quality control on the selection of major components and parts such as thyristors and transformers. For example, for thyristor modules, we have strengthened the screening of the on-state peak voltage V _TM , and tried to control the device temperature rise within a low range; we have also put forward higher requirements for the thyristor gate process. For the main and auxiliary transformers, we also use a toroidal transformer structure with low loss, low temperature rise and high efficiency.

Through several years of efforts, the reliability of "Pandeng" contactless voltage stabilizer has been continuously improved. So far, the average trouble-free operation time of the product has reached 100,000 hours.

4. About the contactless voltage regulator controlled by single chip microcomputer

Many contactless voltage stabilizers on the market currently use single-chip microcomputers to build control systems. Although single-chip microcomputer technology has many advantages and is relatively advanced, it also has weaknesses, namely, anti-interference processing is relatively complex and difficult. For high-power power voltage stabilizers, their working environment, especially the electromagnetic environment, is often relatively harsh, so the circuit structure and control system should strive to be simple and reliable, especially with strong anti-interference capabilities to ensure a higher working reliability. If single-chip microcomputer technology is blindly applied regardless of the occasion in pursuit of fashion, it will be more harm than good.

Therefore, we believe that if there is not much improvement on the main performance indicators of the voltage regulator, we should still be cautious about the application of microcontroller technology in contactless voltage regulators.

V. Overview

In the past, most of the power voltage stabilizers on the market were mechanical carbon brush type. However, the use of carbon brushes and mechanical transmission will inevitably lead to many shortcomings and problems, such as short working life, slow response speed, small carbon brush contact surface affecting output current, fast carbon brush wear and frequent maintenance and replacement. Therefore, contactless voltage stabilizers have become the inevitable choice for most users. With the continuous improvement of the technology and process level of manufacturers, the working reliability of contactless voltage stabilizers has been continuously improved. At the same time, as users continue to deepen their understanding of the product, contactless voltage stabilizers will definitely have a better market prospect.