... 3) The vacuum interrupter houses the contacts and makes up the interrupting chamber 4) It serves as an indoor device and operates ... under the condition of rated 12/17.5KV three phase AC voltage and 50/60Hz ... 3) Rated short circuit breaking current: 25, 31.5, 40KA 4) Mechanical life: 30,000, 20,000, 10,000 times Medium Voltage Vacuum Circuit Breaker