A complete guide to buying universal changeover switches: from principle to selection and application (Part 2)

Main types and series of universal changeover switches

Universal changeover switches have formed multiple series and types according to their structural characteristics, application scenarios and technical parameters. Understanding the characteristics and applicable scope of these different types is crucial for correct selection. Common universal changeover switches on the domestic market mainly include LW5 LW26 LW30 LW12 series, each series has its specific application field and technical characteristics.

The LW5 series is one of the most widely used universal changeover switches, especially suitable for circuits with AC 50Hz, voltage up to 500V, and DC voltage up to 440V. This series of switches can not only be used for the conversion of electrical control circuits, but also can directly control three-phase squirrel cage asynchronous motors with voltage of 380V, 5.5kW and below, to achieve starting, reversible conversion and multi-speed motor speed change and other functions. LW5 series can be divided into two types according to the purpose: main command control and motor control; according to the operation mode, it can be divided into positioning type and self-resetting type; from the appearance of the operator, there are two types: knob type and ball handle type. The mechanical life of this series of switches can reach 100×10⁴ times, and the electrical life is 20×10⁴ times, with high reliability.

LW26 series universal changeover switch is a multi-purpose electrical control component, mainly suitable for electrical circuits with AC 50Hz, rated working voltage 440V and below, DC voltage 240V and below, and rated current from 10A to 160A. This series of products has complete specifications, and the current levels include 10A, 20A, 25A, 32A, 63A, 125A and 160A and other options, which can meet the control needs of different power loads. The rated insulation voltage reaches 660V, with good electrical isolation performance. The mechanical life can reach 0.1×10⁶ times, the electrical life is 0.03×10⁶ times, and the operating frequency is 120 times/hour, which is suitable for occasions where the circuit is not frequently connected or disconnected.

The LW30 series universal changeover switch is a multi-purpose electrical control component, mainly suitable for electrical circuits with AC 50Hz, rated working voltage below 440V, DC voltage below 240V, and rated current from 20A to 100A. This series of products has complete specifications, and the current levels include 20A, 25A, 32A, 40A, 63A, 80A and 100A and other options, which can meet the control needs of different power loads. The rated insulation voltage reaches 690V, with good electrical isolation performance. The product adopts a modular design, and other contact blocks can be added to the 3-pole standard block without removing the entire switch, which greatly improves the convenience of installation and maintenance.

LW12-16 series is another widely used universal changeover switch, mainly used in circuits with AC 50Hz, rated working voltage 380V and below, DC voltage 220V and below. This series can not only convert electrical control circuits and electrical measuring instruments, but also directly control three-phase squirrel cage asynchronous motors of 5.5KW and below. LW12-16 series is divided into two types according to its use: main command control and direct motor control; according to the operation mode, it is more diverse, including positioning type, self-resetting type, positioning self-resetting type and positioning self-resetting with locking device type. This diversity enables LW12-16 series to adapt to more complex control needs.

In addition to the above mainstream series, there are some **special purpose universal changeover switches** on the market, such as LW36-D series, which is suitable for electrical circuits with 50Hz, rated working voltage 440V and below, DC voltage 240V and below. This type of switch usually has more stringent environmental adaptability requirements, such as being able to work normally in an environment where the ambient air temperature does not exceed +40℃ and the average temperature within 24 hours does not exceed +35℃, and the altitude of the installation site does not exceed 2000m.

From the perspective of protection, universal changeover switches can be divided into two types: open type and protective type; according to the type of handle, there are four types: knob, ordinary, machine tool and gun-shaped. These different appearance designs not only affect the aesthetics of the switch, but are also closely related to its use environment and operational convenience. For example, protective switches are more suitable for dusty or humid environments, while gun-shaped handles are convenient for operation in small spaces.

With the advancement of technology, some new universal changeover switches have also added intelligent functions, such as indicator lights to display the switch status, built-in electronic locks to prevent misoperation, and remote monitoring interfaces. Although these functions increase costs, they show obvious advantages in some occasions with high requirements for safety and monitorability, such as rail transit, intelligent buildings, etc.

Understanding the characteristics of these different types and series is the basis for the correct selection of universal changeover switches. When actually selecting a product, in addition to considering the series characteristics, it is also necessary to conduct a comprehensive evaluation based on specific application scenarios, load types, operating frequency and other factors in order to select the most suitable product.