How can permanent magnet mechanisms overcome the speed limitations caused by the large contact gaps in high-voltage vacuum circuit breakers? - Blog

To address the speed limitations of permanent magnet mechanisms resulting from the large contact gaps in high-voltage vacuum circuit breakers, the key solution involves enhancing opening and closing speeds by optimizing the magnetic circuit structure and upgrading control strategies. Specific solutions include:

1. Magnetic Circuit Structure Optimization (Core Method for Increasing Speed)

Establishing an independent magnetic holding circuit: An independent magnetic holding circuit is established at the end of the moving armature, the end of the yoke, or the end positions corresponding to the closed or open states. This measure effectively overcomes or reduces magnetic resistance acting on the moving armature during motion, thereby significantly increasing the circuit breaker's opening and closing speeds.

Optimizing permanent magnet placement: Permanent magnets are fixed to the ends of the yoke or the moving armature (fixed at one or both ends) to optimize the magnetic circuit design and meet the speed requirements of high-capacity, large-gap circuit breakers.

2. Upgrading Drive and Control Strategies

Increasing opening coil current: Building upon the optimized magnetic circuit, the driving current of the opening coil is directly increased to generate greater instantaneous thrust, effectively boosting the opening speed.

Precision closed-loop control: A control unit centered on a Digital Signal Processor (DSP) is used to perform closed-loop regulation of the coil current. This not only increases opening speed to overcome resistance caused by the large gap but also effectively reduces the final opening speed as the contacts reach the preset travel limit; this suppresses contact overshoot and bounce, ensuring operational reliability despite the large gap.

The key to overcoming the operational speed limitations caused by large contact gaps in 12kV permanent magnet mechanisms lies in regulating the coil current via closed-loop control strategies to suppress contact overshoot and bounce during opening. The specific technical solutions are as follows:

Adoption of a dual-coil, monostable permanent magnet mechanism

Optimization of opening performance: A magnetic shunt structure is incorporated into the opening-stroke air gap to reduce the initial ampere-turns required for opening and the permanent magnet holding force during the process; this shortens the opening time and increases the opening speed.

3. Simplification of the control circuit

The dual-coil structure (utilizing separate coils for opening and closing operations) allows the opening coil current to be reduced to below 2A, thereby simplifying the peripheral control circuitry and eliminating the need for complex current polarity reversal controls.

4.Regulation of terminal speed

A control unit centered on a Digital Signal Processor (DSP) dynamically regulates the current in the permanent magnet mechanism's coils, effectively reducing the terminal speed of the contacts during the opening stroke.

5. Suppression of overshoot and rebound

By calibrating the preset travel value for the contacts at the open position, overshoot and rebound are effectively suppressed; this ensures the reliability of the permanent magnet mechanism during large-gap opening operations and enhances the circuit breaker's breaking capacity.

VSM-12 Indoor Permanent Magnetic Vacuum Circuit Breaker