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Vacuum Circuit Breaker VB4-P
The VB4-P vacuum circuit breaker with a spring-operated motor mechanism is designed for use in 10 kV indoor and outdoor switchgear assemblies (AIS or GIS), as well as for retrofit replacement of obsolete circuit breakers installed in earlier KRU and KSO panels.
The circuit breaker is a factory-assembled switching device, consisting of a main housing, three sealed poles, and an integrated spring-operated motor mechanism.
Features and Benefits
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The breaker utilizes sealed cast-resin epoxy poles, ensuring high dielectric strength and long-term insulation reliability.
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When a station auxiliary DC supply is available, the operating spring is automatically charged by the motor. In the absence of auxiliary power, the spring can be manually charged.
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The mechanical design of the VB4-P breaker minimizes switching overvoltages to 1.4 × rated voltage by optimizing the contact separation diagram.
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The lever and cam geometry in the “ON” position mechanically prevents contact chatter or unintentional opening.
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The design allows installation of additional release coils — instantaneous overcurrent release and undervoltage release.
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The stored energy in the spring is sufficient to perform a single auto-reclosing (O-0.3 s-CO) operating cycle.
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The breaker provides monitoring of closing and tripping circuits, with direct status feedback from the operating coils.
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Simple and convenient access to mechanism components and auxiliary contacts facilitates inspection and maintenance.
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The absence of electronic components and electrolytic capacitors extends service life and increases operational reliability.
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The design allows the integration of a motorized truck mechanism for remote racking-in and racking-out of the breaker between the service and test positions.
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The spring operating mechanism ensures low energy consumption; during closing and opening, secondary circuit inrush currents do not exceed 2 A.
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Each breaker undergoes type and routine tests using a dedicated test bench to verify and calibrate mechanical performance parameters — including contact travel timing, pole synchronization, contact velocity, and contact force.
Technical Data — Vacuum Circuit Breaker VB4-P
| Rated voltage, kV | 7.2; 12; 17.5; 24; |
| Rated current, A | 630; 1250; 1600; 2000; 2500; 3150; 4000 |
| Rated short-circuit breaking current, kA | 20; 25; 31.5; 40 |
| Short-time withstand current (3 s), kA | 20; 25; 31.5; 40 |
| Peak withstand current, kA | 51; 64; 80; 102 |
| Rated lightning impulse withstand voltage (1.2/50 μs), kV | 75 |
| Rated power-frequency withstand voltage (1 min), kV | 42 |
| Rated control circuit voltage, V: | |
| – for DC supply | 110; 220 |
| – for AC supply | 110; 220 |
| Operating voltage range (% of Un): | |
| – control and auxiliary circuits | 0.65 – 1.10 |
| – DC trip coils | 0.70 – 1.10 |
| – AC trip coils | 0.65 – 1.20 |
| Power consumption of closing and tripping coils, VA/W | 250 |
| Closing time, s (max) | 0.075 |
| Opening time, s (max) | 0.050 |
| Spring-charging time, s | 15 |
| Pole contact synchronization tolerance, s (max): | |
| – at closing | 0.010 |
| – at opening | 0.005 |
| Rated operating sequence | O – 0.3 s – CO – 180 s – CO |
| Electrical endurance (number of CO operations): | |
| – at rated current | 30,000 |
| – at short-circuit currents (30–60% of rated breaking current) | 200 |
| – at short-circuit currents (60–100% of rated breaking current) | 100 |
| Mechanical endurance (number of CO operations) | 30,000 |
| Contact gap, mm | 20¹ / 51² / 75³ |
| Inter-pole distance, mm | 150¹ / 210¹·² / 275²·³ |
| Overall dimensions, mm: | |
| – width | 450¹ / 570¹·² / 750³ |
| – depth | 407¹ / 412² / 448³ |
| – height | 460¹ / 616² / 637³ |
| Weight, kg | 70 – 260 |
| Service life, years | 25 |
¹ for rated currents 630 A and 1250 A
² for rated currents 1600 A and 2000 A
³ for rated currents 2500 A and above
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Service and Environmental Conditions
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Altitude above sea level: up to 1000 m
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Maximum ambient air temperature: +40 °C
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Minimum ambient air temperature: –25 °C
For lower ambient temperatures, heating elements must be installed inside the switchgear cubicle or in the switchgear room to maintain the air temperature not lower than the specified minimum during circuit breaker operation.
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Relative humidity of ambient air: up to 98 % at +25 °C, with possible condensation of moisture
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Ambient environment: non-explosive, atmosphere type II according to applicable standards
The VB4-P vacuum circuit breakers have been type-tested and certified by the internationally accredited laboratories of EU for compliance with IEC 62271 standards.
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