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Application of refrigeration compressor protectors The refrigeration compressor is a key component in air conditioners and refrigerators, and is often referred to as the \"heart\" of these devices. Since the 1980s, our country has gradually introduced technologies and equipment, and its production capacity has reached around 20 million units. Due to the requirement for high reliability and safety during operation, higher demands are placed on compressor protectors. 1 Function The protector is connected in series with the compressor circuit; it monitors changes in the compressor’s temperature in real time, and based on changes in current, provides accurate and reliable protection for the compressor. Currently, the main type widely used in refrigeration compressors is the snap-action bimetallic protector. It has advantages such as simple structure, reliable operation, ease of use, and low cost. 2 Types Depending on the installation method and functions, there are the following types: 2.1 Based on the installation method, they can be divided into two types: 2.1.1 External protectors Installed on the sealed terminals of the compressor housing. Therefore, the accuracy in measuring the temperature of the induction compressor housing, as well as its operational reliability, are relatively poor, and its application range has certain limitations. However, due to its ease of installation and maintenance as well as low cost, it is generally used in refrigerator compressors and household air-conditioner compressors with low power levels (usually less than 1 PH). 2.1.2 Embedded protectors Installed inside the compressor housing, on the motor coils (bundled to them) or on the sealed terminals (connected to them). Therefore, it offers accurate performance, high reliability, and a wide range of applications (suitable for everything from refrigerator compressors to ordinary air conditioner compressors). However, since it is installed inside the compressor, it is required to be small in size and able to withstand harsh conditions such as high temperatures and pressure changes within the compressor. Therefore, high requirements are placed on its design and manufacturing, such as a sealing performance of 1×10‑9 standard atmospheres·second. Currently, it is widely used in air-conditioning compressors. 2.2 Based on their functions, they can be divided into three types. 2.2.1 Overheat protector: When the compressor’s temperature exceeds its allowable operating range for various reasons, this protector automatically cuts off the circuit, thereby stopping the compressor from operating. Once the compressor temperature drops to the designed range, the circuit is automatically reconnected, thereby ensuring that the compressor operates within an acceptable temperature range and preventing damage or a reduction in its service life. 2.2.2 Overload Protector ① Its main function is to, in cases where abnormal operating conditions such as prolonged overload, increases or decreases in grid voltage affect the performance of the compressor or cause it to burn out, cut off the circuit within a specified time according to design requirements; this is what is referred to as the \"current characteristic\". ②When the compressor stalls due to reasons such as mechanical seizure or an excessively short start-up delay, and the power supply is not cut off in time, this results in \"motor burnout\". This protector can cut off the circuit at a specified current within a specified time period (i.e., the so-called “time characteristic”), thereby preventing accidents. 2.2.3 Overheat and overload protector: This protector combines the functions of the two aforementioned types of products. As a result, it requires higher standards in terms of design and related components; however, it simplifies the compressor’s structure and improves its reliability, which is why it is widely used. 3 Domestic and international production and application status 3.1 External protectors ① External protectors for refrigerator compressors. The production of this product is exemplified by the American company TI; it features automated mass production, mature manufacturing processes, and stable quality. Additionally, there are companies such as Japan’s YAMADA. However, there are still differences in aspects such as production equipment and technical level. Since the 1980s, the country has successively introduced production lines or key equipment for refrigerator compressor protectors. At the same time, there are also many manufacturers that rely on self-developed technologies and processing equipment for production and have reached a considerable scale. After more than a decade of exploration, the current production technology and product quality have reached a mature level, offering significant advantages in terms of price. ②Protective cover for air conditioner compressor. It has a production history of over a decade in the domestic market, but large-scale production has not been achieved. Although a large number of air conditioner compressor production lines have been introduced in China in recent years, this type of protector still relies on imports for supply. Currently, domestic manufacturers of protective devices have set their sights on this product and are investing efforts in its development; there are also signs that it will be adopted by air-conditioning compressor manufacturers. 3.2 Embedded protectors: This product has been developed in China for some time, and certain experience has been accumulated; however, due to various reasons, mass production has not been achieved. Therefore, it is seriously behind the requirements for the localization of air-conditioning compressors. Currently, companies that produce this product in the world include Texas Instruments in the United States and Seiko Manufacturing Co., Ltd. in Japan. 4 Introduction to New Types of Protectors With the continuous development of refrigeration compressor production, new requirements have been placed on protectors, and some protectors with unique functions have emerged that meet the needs of compressor production more effectively. 4.1 Meltable non-recoverable protector Under normal circumstances, the protector helps to protect the compressor from damage, but it cannot fulfill its protective function in the following situations: ① When there are certain permanent faults, such as mechanical binding of the compressor, and the protector has exceeded its service life. ②Frequent failures cause the protector to exceed its service life. ③When it is impossible to disconnect due to quality issues with the protector itself. If the circuit is not forcibly disconnected under the above circumstances, more serious accidents will inevitably occur, and incidents that could endanger personal safety such as compressor explosions may even take place. The emergence of fusible (surface-mounted and embedded) protectors has well met this requirement. In such situations, this protector can, thanks to its specific design, cut the circuit permanently, acting in a manner similar to a \"fuse\" and thus providing reliable protection for the compressor, preventing it from exploding. This product was gradually introduced and applied around 1997, achieving good results. 4.2 Plug-in Embedded Protectors In the past, most embedded protectors were attached to the motor stator windings using binding methods in order to accurately detect changes in temperature; however, this approach was very inconvenient for installation, it affected the production process in compressor assembly lines, and it also resulted in higher costs. To improve the aforementioned situation, a plug-in protector that is directly inserted into the sealed terminal effectively solves these problems. This protector senses the overall temperature of the compressor’s exhaust gas, etc.; it offers the convenience of external installation while also providing the reliability of underground operation, with relatively low costs as well. 4.3 Embedded protectors with integrated overheat and overload protection functions Overheat and overload protectors were generally used in external types earlier on; embedded protectors, on the other hand, usually only had overload protection functionality in the past, with overheat protection being handled by separate protectors. Although they have distinct functions, they reduce the overall reliability of the compressor and increase costs; therefore, overheat and overload types are currently more commonly used in designs. With the emergence of variable-frequency air conditioner compressors, the requirements for protectors have also changed. For example, it is sufficient to use a protector with an overheat protection function. Such protectors come in forms such as externally mounted types, plug-in buried types, and tied-in buried types; however, in practice, the plug-in buried type seems to be a more reasonable and effective approach. It should be noted that for compressors equipped with built-in protectors, reliable (dual) protection is provided against abnormal operating conditions such as excessively high or low operating voltage and too short starting delay times. In this sense, it is unnecessary for air conditioner manufacturers to implement functions such as voltage monitoring and start-up delay setting in order to protect the compressor. 5 Conclusions In summary, when selecting a protector, from the perspective of protection performance, it is advisable to use an embedded protector ； However, in terms of cost-effectiveness and ease of use and maintenance, external protectors still have their advantages. Therefore, it is highly possible and necessary to make design improvements to existing external protectors so that they can achieve the same effectiveness as internal protectors, and they will surely be accepted by the market. Related articles: Operating characteristics of screw-type refrigeration compressors; The development history of refrigeration compressors; A new type of synchronous rotary refrigeration compressor; Analysis of research hotspots in small refrigeration compressors 3; Analysis of research hotspots in small refrigeration compressors 2; The cylinder block of piston-type refrigeration compressors; Safety valves in piston-type refrigeration compressors; Connecting rods in piston-type refrigeration compressors; New energy-saving refrigeration compressors; How to choose lubricating oil for centrifugal refrigeration compressors. Last edited by 527728688 on 2009-3-18 20:01.]