Circuit improvement apparatus having combination current limiting fuse and resettable vacuum switch to prevent single-phasing of three-phase loads

A current interrupting apparatus adapted to be interposed in a multiple phase electrical circuit, the apparatus comprising:

• a current limiting fuse interposed in each phase of the circuit and including a sealed housing and a fusible element within the housing which fuses in response to a fault current of a first predetermined magnitude experienced by the circuit, the housing including structure for retaining the energy of interruption with the housing upon fusing of the fusible element;
• current interrupting means electrically connected in series with each current limiting fuse for interrupting the current through the circuit, each current interrupting means including a pair of normally closed electrical contacts and a mechanism for opening the contacts in response to a fault current of a second predetermined magnitude different from the first predetermined magnitude;
• and
• current interrupter triggering means for triggering operation of the mechanisms of all of the current interrupting means in response to fusing of the fusible element of any of the current limiting fuses to protect the circuit from the effects of single phasing,
• the current interrupter triggering means comprising a triggering circuit including a solenoid electrically connected in parallel with each of the current limiting fuses and means for operably connecting each solenoid to all of the mechanisms.

A current interrupting apparatus adapted to be interposed in a single phase electrical circuit, the apparatus comprising:

• a fuse interposed in the circuit and including a fusible element which fuses in response to a fault current of a first predetermined magnitude experienced by the circuit;
• a current interrupter electrically connected in series with the fuse for interrupting the current through the circuit, the current interrupter including a pair of normally closed electrical contacts and opening means for moving the pair of contacts to an open position;
• and
• current interrupter triggering means for triggering operation of the opening means of the current interrupter in response to fusing of the fusible element of the fuse to protect the circuit from the effects of a fault current in the circuit, the current interrupter triggering means including a triggering circuit with a solenoid electrically connected in parallel with the fuse and operable upon fusing of the fusible element of the fuse to trigger operation of the opening means of the current interrupter.

A current interrupting apparatus adapted to be interposed in a multiple phase electrical circuit, the apparatus comprising:

• a fuse interposed in each phase of the circuit and including a fusible element which fuses in response to a fault current of a first predetermined magnitude experienced by the circuit;
• a current interrupter electrically connected in series with each fuse for interrupting the current through the circuit, each current interrupter including a pair of normally closed electrical contacts and opening means for moving the pair of contacts to an open position;
• and
• current interrupter triggering means for triggering operation of the opening means of all of the current interrupters in response to fusing of the fusible element of any of the fuses to protect the circuit from the effects of single phasing, the current interrupter triggering means including a triggering circuit with a solenoid electrically connected in parallel with each fuse and operable upon fusing of the fusible element of the fuse to trigger operation of the opening means of all of the current interrupters.