What is the difference between permanent magnet operating mechanism and spring operating mechanism?

Compared with traditional operating mechanisms, permanent magnetic operating mechanisms have fewer components, only 7% of the components of traditional circuit breaker operating mechanisms. They eliminate the need for mechanical tripping and locking devices, resulting in fewer failure points, high reliability, and a long service life. The permanent magnetic operating mechanism has a lifespan of over 100,000 cycles, making it suitable for frequent operation and applications such as high-reliability substations. The permanent magnetic mechanism overcomes the shortcomings of traditional spring and electromagnetic mechanisms. By utilizing permanent magnetic materials to maintain the open and closed positions of the vacuum circuit breaker and maintain its operation, it achieves high reliability and stable operation in frequent operation and harsh environments.

Below I will compare and explain them in detail from the aspects of working principles, advantages and disadvantages, application scenarios, etc.

Spring Mechanism

The spring mechanism is a traditional and widely used operating mechanism with mature and reliable technology.

1. Working Principle
The core of the spring mechanism is to use the energy stored in the spring to actuate the circuit breaker to open or close. It typically consists of a closing spring and an opening spring.

Energy Charging: A motor (manual or electric) pulls a ratchet, compressing the closing spring to store energy. Once energy is stored, a mechanical indicator (such as a "Charged" sign) is displayed, and the state is maintained.

Closing Operation: When a closing signal is received, the closing release is released, rapidly releasing the energy stored in the closing spring, pushing the linkage mechanism and closing the circuit breaker's main contacts. During the closing process, the opening spring is typically compressed and stored to prepare for the next opening.

Opening Operation: When an opening signal is received, the opening release is released, and the energy from the opening spring pushes the mechanism, rapidly opening the circuit breaker.

A simple analogy: it is like stringing a crossbow (storing energy), then pulling the trigger (release of the tripper) to shoot the arrow (closing/opening the circuit breaker).

2. Advantages
Mature Technology: With a long history and extensive experience in design, manufacturing, and operation and maintenance.

High Reliability: Purely mechanical structure, clear logic, and strong anti-interference capabilities.

Easy Maintenance: Highly standardized mechanical components make the structure familiar to maintenance personnel, making on-site maintenance and part replacement easy.

No Continuous Power Supply Required: Once energy storage is complete, the energy required for operation is stored in the spring. Operation requires no high-power power; a simple trip signal current is sufficient.

3. Disadvantages
Complex Structure: Consisting of hundreds of parts, including gears, cams, connecting rods, and pawls, the system is complex and cumbersome.

Mechanical Wear: Friction and impact between numerous mechanical parts can cause wear over time, requiring regular lubrication and maintenance.

Noise: The energy storage motor generates a loud mechanical noise when operating and the spring releases.

High Energy Consumption: The energy storage motor is high-powered, consuming a significant amount of electricity per energy storage cycle.

Risk of Misoperation: The complex mechanical linkage can malfunction if improperly maintained.

Permanent Magnetic Mechanis

The permanent magnetic mechanism is a new technology developed in recent years, primarily used in vacuum circuit breakers, particularly those in the 12kV and 40.5kV voltage ranges.

1. Working Principle
The core of the permanent magnetic mechanism is the interaction between the magnetic field generated by a permanent magnet (a strong magnetic material such as neodymium iron boron) and the electromagnetic field generated by the opening/closing coil, directly driving the moving iron core (which is directly connected to the moving contact of the vacuum interrupter) to complete the opening and closing operations.

The bistable design is its essence. Through a clever magnetic circuit design, the attractive force of the permanent magnet can stabilize the moving iron core in both the "open" and "closed" positions without the need for any mechanical latch.

Closing operation: A pulse current is applied to the closing coil, generating a magnetic field aligned with the magnetic field of the permanent magnet, which together drive the moving iron core toward the closed position. Once in position, the attractive force of the permanent magnet keeps it firmly in that position.

Opening operation: A pulse current is applied to the opening coil, generating a magnetic field opposite to that of the permanent magnet, counteracting the permanent magnet's holding force. With the help of the discharged energy storage capacitor, the moving iron core moves toward the open position. Once in the open position, it is again held in place by the permanent magnet's attraction.

Capacitor energy storage: An electronic control system operates within the mechanism. Normally, a low-power power supply charges the capacitor to store energy. During operation, the capacitor instantly discharges to the opening/closing coil, providing the required high current pulse.

A simple analogy: a magnet attracts a piece of iron, with two stable positions (open and closed). You need to apply a brief electrical "push" (closing coil) or "pull" (opening coil) to force it to switch from one position to the other, and then the magnet itself attracts and holds it.

2. Advantages
Simple Structure: The number of parts is extremely small (typically less than 50), primarily consisting of coils, cores, and permanent magnets, with virtually no complex mechanical transmission components.

High Reliability: Due to the small number of parts, mechanical wear points are minimal, resulting in a long lifespan and theoretically higher reliability.

Stable Operating Characteristics: The operating power is determined by capacitor discharge, ensuring consistent speed and force throughout each operation, unaffected by human or environmental factors.

Low Energy Consumption: Energy is consumed only during the instant of opening and closing, and the capacitors provide power, minimizing impact on the upstream power supply. The power consumption during normal standby operation is extremely low.

Maintenance-Free: Designed to be "maintenance-free" or "low-maintenance," this reduces the workload of regular inspections.

3.Disadvantages
High control and power requirements: Its proper operation is highly dependent on the electronic control unit (CPU) and energy storage capacitors. If the control system or capacitors fail, the entire mechanism will cease to operate.

High cost: High-performance NdFeB permanent magnets and electronic control units are relatively expensive.

Risk of residual magnetism and demagnetization: In extreme cases (such as a coil short circuit), the strong magnetic field may disappear (demagnetization), causing the mechanism to fail. This cannot be repaired on-site and requires a return to the factory.

Complex fault diagnosis and repair: Specialized electronic equipment is required to diagnose control circuit and magnetic circuit problems, which may be difficult for traditional electricians to handle.

Comparison Summary Table

How to Choose?

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Choosing a spring mechanism: Prioritizing the technology's traditional maturity, ease of field maintenance, and initial investment cost, as well as applications where trust in electronic control systems is limited. Spring mechanisms offer advantages due to their durability and maintainability, particularly in applications requiring frequent operation (such as in the metallurgical industry).

Choosing a permanent magnet mechanism: Prioritizing low or no maintenance, high reliability, and low energy consumption. These mechanisms are suitable for intelligent, unmanned new substations, wind power plants, photovoltaic power plants, railways, and other applications that demand a high degree of automation. They are an ideal choice for high-voltage distribution circuit breakers in the development of smart grids.

In short, both technologies are excellent, and there is no absolute superiority or inferiority. Spring mechanisms are the experienced and proven "veterans," while permanent magnet mechanisms are the technologically advanced "rising stars" that represent the future. The choice depends on specific application requirements, investment budget, and maintenance strategy.

If you have any more specific technical questions or want to learn about mechanism , please feel free to let me know and I'd be happy to continue helping you!

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