usa ka Artikulo aron Masabtan Kung Paunsa ang Pagpili sa Mekanikal nga mga Parameter sa Vacuum Circuit Breakers

1. Rated Contact Gap

Kini nga ang vacuum circuit breaker adunay open position, ang distance tali sa moving ug fixed contacts sa sulod sa vacuum interrupter gitawag og rated contact gap. Kini nga parametro nadirekta gihatagan og epekto pinaagi sa daghang mga factor sama sa breaker’s rated voltage, operating conditions, nature sa interrupting current, contact material, ug dielectric strength sa vacuum gap. Kini primariya depende sa rated voltage ug contact material.

Ang rated contact gap makadaghan ang epekto sa insulation performance. Kon ang gap madugay gikan sa zero, ang dielectric strength maayo. Apan, gikan sa usa ka certain point, pagmadugay pa sa gap wala na maghatag og dako nga epekto sa insulation performance ug mao usab mahimong mapasabot sa mechanical life sa interrupter.

Batasan sa installation, operation, ug maintenance experience, ang typical rated contact gap ranges mao kini:

• 6kV ug below: 4–8 mm

• 10kV ug below: 8–12 mm

• 35kV: 20–40 mm

2. Contact Travel (Overtravel)

Ang contact travel kinahanglan isipon aron siguradohon nga ang sufficient contact pressure makabalaka bisan human sa contact wear. Kini usab naghatag og initial kinetic energy sa moving contact sa panahon sa opening, nag-increase sa initial opening speed aron maputli ang welded joints, reduce arcing time, ug accelerate dielectric recovery. Sa panahon sa closing, kini naghatag og smooth buffering sa contact spring, minimising ang contact bounce.

Kon ang contact travel gamay ra:

• Insufficient contact pressure human sa wear

• Gamay nga initial opening speed, affecting breaking capacity ug thermal stability

• Severe closing bounce ug vibration

Kon ang contact travel dako:

• Increased closing energy required

• Reduced reliability sa closing operation

Typically, ang contact travel 20%–40% sa rated contact gap. Para sa 10kV vacuum circuit breakers, kini general 3–4 mm.

3. Contact Operating Pressure

Ang operating pressure sa vacuum circuit breaker’s contacts naghimo og significant impact sa performance. Kini sum sa vacuum interrupter’s inherent self-closing force ug ang contact spring force. Proper selection kinahanglan molambo sa apat nga requirements:

• Maintain contact resistance within specified limits

• Meet dynamic stability test requirements

• Suppress closing bounce

• Reduce opening vibration

Closing under short-circuit current ang pinakamas demanding condition: pre-arc currents generate electromagnetic repulsion, causing contact bounce, while closing speed is at its lowest. This scenario critically tests whether the contact pressure is sufficient.

Kon ang contact pressure gamay ra:

• Increased closing bounce time

• Higher main circuit resistance, leading to excessive temperature rise during continuous operation

Kon ang contact pressure dako:

• Increased spring force (since self-closing force is constant)

• Higher closing energy requirement

• Greater impact and vibration on the vacuum interrupter, risking damage

Sa practice, ang contact electromagnetic force depends not only on peak short-circuit current but also on contact structure, size, hardness, and opening speed. A comprehensive approach is essential.

Empirical data for contact pressure based on interrupting current:

• 12.5 kA: 50 kg

• 16 kA: 70 kg

• 20 kA: 90–120 kg

• 31.5 kA: 140–180 kg

• 40 kA: 230–250 kg

4. Opening Speed

Ang opening speed direkta ang epekto sa rate sa dielectric strength recovers after current zero. Kon ang recovery sa dielectric strength mas gamay sa rising recovery voltage, arc re-ignition may occur. Aron i-prevent ang re-ignition ug minimize arcing time, adequate opening speed essential.

Ang opening speed primarily depende sa rated voltage. Para sa fixed voltage ug contact gap, ang required speed varies sa interrupting current, load type, ug recovery voltage. Higher interrupting currents ug capacitive currents (with high recovery voltage) require higher opening speeds.

Typical opening speed para sa 10kV vacuum breakers: 0.8–1.2 m/s, sometimes exceeding 1.5 m/s.

Sa practice, ang initial opening speed (measured over the first few millimeters) has a greater impact on breaking performance than average speed. High-performance ug 35kV vacuum breakers often specify this initial speed.

While higher speed seems beneficial, excessive speed increases opening vibration ug over-travel, intensifying stress on the bellows ug leading to premature fatigue ug leakage. It also increases mechanical stress on the mechanism, risking component failure.

5. Closing Speed

Due to the high static dielectric strength of vacuum interrupters at rated gap, the required closing speed is significantly lower than opening speed. Adequate closing speed is necessary to minimize pre-arc electrical erosion and prevent contact welding. However, excessive closing speed increases closing energy and subjects the interrupter to greater impact, reducing service life.

Typical closing speed para sa 10kV vacuum breakers: 0.4–0.7 m/s, up to 0.8–1.2 m/s if required.

6. Closing Bounce Time

Ang closing bounce time usa ka key indicator sa vacuum circuit breaker performance. Kini influenced sa contact pressure, closing speed, contact gap, contact material, interrupter design, breaker structure, ug installation/adjustment quality.

Shorter bounce time indicates better performance. Excessive bounce causes severe electrical erosion, increases risk of overvoltage, ug may lead to contact welding during short-circuit or capacitor switching operations, as well as thermal stability tests. Prolonged bounce also accelerates bellows fatigue.

Para sa 10kV vacuum breakers with copper-chromium contacts, ang closing bounce should not exceed 2 ms. Para sa uban pang materials, kini may be slightly higher but should not exceed 5 ms.

7. Three-Pole Synchronism

Ang three-pole synchronism measures the degree of simultaneity in closing or opening of the three poles. Since opening ug closing synchronism values are similar, only closing synchronism is typically specified.

Poor synchronism severely affects breaking capacity ug prolongs arcing time. Due to fast operating speeds ug small gaps, precise adjustment can easily meet requirements. Ang closing synchronism is generally required to be within 1 ms.

8. Alignment of Moving and Fixed Contacts (Coaxiality)

Proper coaxial alignment of moving ug fixed contacts critical sa vacuum interrupter performance ug ensured through manufacturing precision. Whether this alignment is maintained after installation depends on the operating mechanism type ug assembly process.

Para sa suspended mechanisms, ang alignment primarily determined sa mechanism itself. Para sa floor-mounted types, ang mechanical alignment equally important. During installation, avoid applying shear or lateral forces to the interrupter.

Typical coaxiality tolerance: ≤2 mm.