Why Reduced Opening and Closing Speeds in Circuit Breakers

1. Operating Power Supply Limitations

The operating power supply provides the indirect energy needed for a circuit breaker to open and close, and any instability here can significantly impact its speed:

• Electromagnetic Mechanism: If the power supply voltage drops, the magnetic core in the electromagnetic mechanism moves sluggishly, reducing the breaker’s closing speed. The lower voltage means the closing coil has less energy, so the magnetic core cannot accelerate quickly enough, causing a delayed or incomplete closure.
• Hydraulic Mechanism: When the valve openings in the hydraulic system are too small, the system cannot instantaneously release or build up the hydraulic pressure needed. For example, during opening, if high-pressure oil cannot exit the closing chamber promptly due to limited valve size, the opening speed will drop. Similarly, insufficient valve size during closing prevents the oil pressure from building quickly, resulting in a slower closing action.

2. Insufficient Operating Energy

The energy available in the operating mechanism—whether spring, hydraulic, or pneumatic—directly affects the breaker’s responsiveness:

• Spring Mechanism: If the stored energy in the spring is insufficient, either due to a lack of proper pre-compression or wear over time, the speed of both opening and closing actions slows down.
• Hydraulic Mechanism: Low hydraulic pressure fails to deliver the necessary force to move the circuit breaker contacts at the required speed.
• Pneumatic Mechanism: If the closing spring weakens or fails, the closing speed is notably reduced, as the mechanism can no longer push the contacts together with adequate force.

3. Operational Mechanism Adjustments

Poor or incorrect adjustments in the operational mechanisms can introduce various inefficiencies:

• Electromagnetic Mechanisms: Issues like premature auxiliary switch operation, polarity errors in coil connections, or excessive heating in the closing coil cause the breaker to misfire or slow down. Additionally, if the closing rod is too short, or the magnetic core is restricted, this will limit the travel range or make movements sluggish.
• Spring Mechanism: When the opening spring lacks force, the opening speed suffers. Similarly, if there is any stickiness or mechanical friction in the connecting rods, the overall movement slows.
• Hydraulic Mechanism: Even with normal operating voltage and pressure, factors such as small valve openings in the system can cause delays. For example, an insufficient bleed hole in the secondary valve reduces the opening speed, while a restricted throttle pad at the closing end can lower the closing speed specifically. Obstructions in the hydraulic tubing and inflexible piston movement can further impede both opening and closing actions.

4. Circuit Breaker Body Adjustments

Physical adjustments and mechanical conditions of the circuit breaker’s main body affect its speed:

• Excessive Over-Travel: If the breaker’s contacts move further than necessary (over-travel), it increases the overall time needed for the operation, reducing speed.
• High Contact Pressure: Excessive pressure between contacts requires more energy to separate or close them, leading to slower speeds, especially during opening.
• Mechanical Resistance: Issues such as sticking in the transmission system, variations in buffer effects, or holding the contact tips too far apart all hinder the speed. These factors create additional resistance in the breaker, reducing the speed by requiring extra force and time to complete each action.

By understanding these causes and adjusting the power, energy sources, operational mechanisms, and physical settings, we can ensure circuit breakers operate at their designed speeds, maintaining safety and efficiency in electrical systems.