Spring operating mechanism
The spring operating mechanism consists of four parts: spring energy storage, closing maintenance, opening maintenance, and opening. It comprises approximately 200 components and utilizes the energy stored in the spring's tension and contraction to control the circuit breaker's closing and opening operations. The storage of spring energy is achieved through the operation of the energy storage motor reduction mechanism, while the circuit breaker's closing and opening actions are controlled by the closing and opening coils. Therefore, the energy required for the circuit breaker's closing and opening operations depends on the energy stored in the spring and is independent of the magnitude of the electromagnetic force, thus requiring relatively small closing and opening currents.
The main advantages of spring-operated mechanisms are:
Low closing and opening currents, eliminating the need for high-power operating power supplies;
Remote electric energy storage for electric closing and opening, or local manual energy storage for manual closing and opening, allowing for manual closing and opening even when the operating power supply is unavailable or the operating mechanism refuses to operate electrically; Fast closing and opening speeds, unaffected by power supply voltage fluctuations, and rapid automatic reclosing;
Low power energy storage motor, usable for both AC and DC;
Spring-operated mechanisms allow for optimal energy transfer matching and enable the same operating mechanism to be used for circuit breakers with various breaking current specifications, simply by selecting different energy storage springs, resulting in excellent cost-effectiveness.
The main disadvantages of spring-operated mechanisms are:
The structure is relatively complex, the manufacturing process is complex, high machining precision is required, and the manufacturing cost is relatively high;
The operating force is large, requiring high strength of components;
Mechanical failures are prone to occur, causing the operating mechanism to fail to operate, burning out the closing coil or limit switch;
False tripping occurs, and sometimes after a false trip, the circuit breaker cannot be fully opened, making it impossible to determine its closing or opening position;
The opening speed characteristics are poor.
Permanent magnet operating mechanism
The permanent magnet operating mechanism employs a completely new working principle and structure, consisting of a permanent magnet, a closing coil, and a opening coil. It eliminates the moving links, release/locking devices, and other components found in spring and electromagnetic operating mechanisms. Its simple structure and minimal number of parts (approximately 50) result in only one main moving part during operation, leading to high reliability. It utilizes a permanent magnet to maintain the circuit breaker's position, making it an electromagnetically operated, permanently magnet-held, and electronically controlled operating mechanism.
The working principle of the permanent magnet operating mechanism: When the closing coil is energized, it generates a magnetic flux in the upper part of the magnetic circuit in the opposite direction to that of the permanent magnet. The magnetic force generated by the superposition of the two magnetic fields causes the moving iron core to move downward. When it has moved about halfway, due to the reduction of the air gap in the lower part of the magnetic circuit, the magnetic lines of force of the permanent magnet shift to the lower part. At this time, the magnetic field of the closing coil is in the same direction as the magnetic field of the permanent magnet, thereby accelerating the moving iron core to move downward, and finally reaching the closed position. At this time, the closing current disappears, and the permanent magnet uses the low magnetic impedance channel provided by the moving and stationary iron cores to keep the moving iron core in the stable closed position. When the opening coil is energized, it generates a magnetic flux in the lower part of the magnetic circuit in the opposite direction to that of the permanent magnet. The magnetic force generated by the superposition of the two magnetic fields causes the moving iron core to move upward. When it has moved about halfway, due to the reduction of the air gap in the upper part of the magnetic circuit, the magnetic lines of force of the permanent magnet shift to the upper part. At this time, the magnetic field of the opening coil is in the same direction as the magnetic field of the permanent magnet, thereby accelerating the moving iron core to move upward, and finally reaching the open position. At this time, the opening current disappears, and the permanent magnet uses the low magnetic impedance channel provided by the moving and stationary iron cores to keep the moving iron core in the stable open position.
The main advantages of permanent magnet operating mechanisms are:
They employ a bistable, dual-coil mechanism. The opening and closing operations of the permanent magnet operating mechanism are achieved through opening and closing coils. The permanent magnet works in conjunction with the coils, effectively solving the problem of requiring high power energy for opening and closing. Because the magnetic field energy provided by the permanent magnet can be used for the opening and closing operation, the energy required by the coils is reduced, thus eliminating the need for large operating currents.
The up-and-down movement of the moving iron core, via the crank arm and insulating pull rod, acts on the moving contacts of the circuit breaker's vacuum interrupter, realizing the opening or closing of the circuit breaker. This replaces the traditional mechanical locking method, greatly simplifying the mechanical structure, reducing consumables, lowering costs, reducing potential failure points, significantly improving the reliability of mechanical operation, and enabling maintenance-free operation, saving on maintenance costs.
The permanent magnet operating mechanism boasts a near-perpetually persistent permanent magnet force, a lifespan of up to 100,000 cycles, and uses electromagnetic force for opening and closing operations while maintaining a bistable position with permanent magnet force. This simplifies the transmission mechanism, reduces energy consumption and noise, and offers a lifespan more than three times longer than electromagnetic and spring operating mechanisms.
The auxiliary switch utilizes a contactless, component-free, wear-free, and bounce-free electronic proximity switch, eliminating contact problems, ensuring reliable operation, and unaffected by external environmental factors. It also features a long lifespan, high reliability, and eliminates contact bounce issues.
Synchronous zero-crossing switching technology is employed. Under the control of the electronic control system, the circuit breaker's moving and stationary contacts close when the system voltage waveform crosses zero and open when the current waveform crosses zero, generating very small inrush currents and overvoltages. This reduces the impact of operation on the power grid and equipment. In contrast, the operation of electromagnetic and spring operating mechanisms is random, resulting in high-amplitude inrush currents and overvoltages, causing significant impact on the power grid and equipment.
The permanent magnet operating mechanism can perform local/remote opening and closing operations, as well as protection closing and reclosing functions, and can be manually opened. Because the power supply capacity required for operation is small, a capacitor is used as the direct power supply for tripping and closing. The capacitor has a short charging time, small charging current, and strong impact resistance, and can still perform opening and closing operations on the circuit breaker after a power outage.
The main disadvantages of permanent magnet operating mechanisms are:
They cannot be manually closed. After the operating power is lost and the capacitor is depleted, if the capacitor cannot be recharged, the closing operation cannot be performed again.
Manual opening requires a sufficiently high initial opening speed, necessitating significant force; otherwise, the opening operation cannot be performed.
The quality of the energy storage capacitors is inconsistent and difficult to guarantee.
It is difficult to obtain ideal opening speed characteristics.
It is difficult to improve the opening output power of the permanent magnet operating mechanism.
Comparison
Features and Dimensions | Spring Operating Mechanism | Permanent Magnet Operating Mechanism |
|---|---|---|
| Technology Maturity | It is very mature, widely used, and has a long history of operation and a large user base. | Newer technologies, while developing rapidly, lack sufficient operational experience and long-term data accumulation. |
| Structure and Reliability | It has a complex structure with hundreds of parts, including numerous mechanical components such as connecting rods and latches. It has many potential points of failure and requires high precision in manufacturing, high-quality materials, and proper maintenance. | With an extremely simple structure and only one main moving part, it eliminates the need for mechanical release or locking devices. This fundamentally reduces the sources of failure, extending the mechanical life to over 100,000 cycles and easily achieving maintenance-free operation. |
| Operating Performance | It has a fast operating speed (about 50ms), but its output characteristics are not well matched with the requirements of vacuum circuit breakers, and it needs to be compensated by a complex cam linkage mechanism. | It features ultra-fast response (up to 20ms) and output characteristics that are perfectly matched with vacuum circuit breakers, resulting in crisp and clean action. |
| Electrical Control | It is simple to control, with the opening and closing relying on a traditional electromagnetic coil to control the latch. It is not sensitive to power supply voltage fluctuations and operates stably. | The control process is complex, relying on energy storage capacitors, power electronic devices, and intelligent controllers. It is susceptible to electromagnetic interference, and the quality stability of the energy storage capacitors is currently a major technological weakness. |
| Power Supply and Power Consumption | The closing power is stored in the spring, so the closing and opening currents are small (1.5A-2.5A), and the requirements for the DC power supply are not high. The motor's energy storage capacity is only a few hundred watts. | The auxiliary power requirement is extremely small (<1A), but the capacitor needs to release a high-power pulse (up to 2600W) instantaneously when closing and opening the circuit breaker. |
| Operating methods | Extremely flexible. It can be electrically powered for energy storage and operation, or manually powered for energy storage and switching on/off when there is no power supply, providing strong emergency operation capabilities. | Manual closing and opening are not supported. Although an emergency opening terminal is provided, it requires an external instantaneous high current signal to trigger, making emergency operation inconvenient. |
| Cost | It has lower costs and a significant price advantage. | It is more expensive, currently costing significantly more than spring mechanisms. |
| Environmental adaptability | It is sensitive to the environment; the lubricant may dry out or deteriorate, and the parts may rust, affecting reliability. | It is highly adaptable to various environments, thanks to its simple structure and sealed design, enabling it to better cope with harsh conditions. |
How to choose
If you prioritize ultimate reliability and superior performance, and have a sufficient budget: the permanent magnet mechanism is undoubtedly the better choice. It is particularly suitable for locations with extremely high requirements for power supply continuity, difficult maintenance (such as offshore wind farms and remote areas), or frequent operation. Its intelligent phase-selective closing function effectively suppresses operational overvoltages and inrush currents, making it ideal for switching capacitor banks and other equipment sensitive to transient processes.
If your application is general, and you value technological maturity, cost control, and ease of operation: then the time-tested spring mechanism remains the safest and most economical choice. It is widely applicable in various substations, factories, buildings, and other general applications. Its manual operation capability is a crucial safety feature in emergencies such as loss of substation power.
Contact Us
Shaanxi Huadian has adopted the advantages of a minimalist permanent magnet mechanism, perfectly matching its output characteristics with the vacuum interrupter. The main operating circuit eliminates complex mechanical interlocks and tripping devices, significantly reducing moving parts and fundamentally lowering the failure rate, achieving true long lifespan and maintenance-free operation. It retains the core emergency advantage of the spring mechanism. Even in extreme situations such as loss of station power or permanent magnet controller failure, you can still perform emergency closing operations through simple manual energy storage. This is not just a mechanism, but a reliable "physical backup" in critical moments. For inquiries, please contact us:pannie@hdswitchgear.com.
