Certain applications, especially in the industry, need high and up to very high numbers of operating cycles. For example, operation of arc furnaces requires more than 100 operating cycles a day.
The vacuum circuit-breaker type 3AH4 up to 36 kV is designed for extremely high numbers of operating cycles: It controls 60,000 / 120,000 operating cycles.
Minimum maintenance work, such as greasing of operating mechanisms after 10,000 operating cycles and replacement of vacuum interrupters after 30,000 operating cycles, preserves the reliability of these circuit-breakers throughout their entire service life – despite high mechanical stress.
Reference : siemens (siemens\power distribution\Medium Voltage Indoor Devices\Indoor Vacuum Circuit Breaker)
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Vacuum Circuit-Breaker 3AH4