• HB3-51 5-15kV, 200 AMP Continuous, 2,000 Amp Symmetric Interrupt
  • HC3-73 5-15kV, 600 AMP Continuous, 12,000 Amp Symmetric Interrupt
  • HC3-75 5-15kV, 600-1200 AMP Continuous, 18,000 Amp Symmetric Interrupt
  • HD3-79 5-15kV, 600-1200 AMP Continuous, 28,000 Amp Symmetric Interrupt
  • HD3-85 16-38kV, 600 AMP Continuous, 16,000 Amp Symmetric Interrupt

Step Start Power Switching System Overview

1 Cycle Interrupt Time 
The Step-Start Vacuum Circuit Breaker/ Power Controller is designed for extra heavy duty repeated fault, crobar and load interruption for sensitive equipment. It is designed to limit initial closing inrush current to approximately load or other maximum current with an adjustable step delay.

It is also designed for high speed crobar and other load fault interruption. A 50 volts 10 microseconds or longer pulse signal initiates a vacuum contact parting time of 7 to 10 milliseconds. Most faults will be interrupted in less than 1 cycle (17 milliseconds).

If required, line-side over-current sensing CT's can be built-in. Also, if required, instantaneous and very inverse time line over-current relays can be set to coordinate with HV fuses to prevent unnecessary HV fuse damage. Potential transformers, meters, loss of phase tripping, and a complete fused load break air disconnect switch system are also available.

In addition to the high speed ½ to 1 cycle load side fault tripping, instantaneous line side trip contact parting times can be deliberately delayed approximately 1 to 2 cycles, depending on the requirements, and as a result, backup tripping is in the order of 20 to 40 milliseconds. Full interruption is nominally within 8 milliseconds or less (usually first current zero) after vacuum contact parting, providing 2 to 3 cycles interrupt from the line or ground fault-sensing relays. Where required, Vacuum Circuit Breaker Contacts are automatically locked out from opening for line faults above 50% to 80% interrupt capacity to reduce unnecessary erosion of Vacuum Circuit Breaker Contacts, although the Circuit Breaker is actually capable of interrupting it's full current rating if necessary. Operations counters are supplied, with fault trips and total operations counted separately.

Automatic dropout with loss of control power or interlocks is incorporated. Loss of stored energy will not prevent it from dropping out. Loss of voltage dropout can be delayed 80 to 120 milliseconds to prevent unnecessary dropouts from momentary loss of control power due to relay, microswitch, of other interlock contact bounce. Loss of control voltage can activate the anti-pump reset relay without adding to the trip count.

The metal enclosure is designed with hinged front door and removable side, rear, and top panels (where required) for easy access. It is available for cable entrance, bushing entrance or direct bus connection.

Please read on for a more detailed description and philosophy of the Step-Start Vacuum Circuit Breaker System.

Detailed Information

Specifications are for reference only and are subject to change.
Contact Ross Engineering Corp. for current information.