Vacuum Load Break Switch

The information contained in this manual is sufficient for a technician or maintenance mechanic to confidently install, operate, and maintain models D-4200, D-4270, D-4250, and D-4275 Vacuum Load Break Switch.

The SMC line of Vacuum Load Break Switchs are designed to protectively disrupt the electrical circuit upon signal. The switch may be closed by operating the switch handle manually or by an electrical signal if the unit is equipped with a remote closing device. It may be opened manually or electrically by optional undervoltage and/or shunt trip devices.

The standard visible disconnect is a visual means of circuit interruption and also a means of grounding the output terminals.

The SMC line of Vacuum Load Break Switchs may be used in circuits where neither the voltage nor short circuit interrupting currents exceed the rated maximums.

Rated maximums are as follows:

  • Rating: 600 Ampere Continuous
  • Interrupting: 2,000 Amp Symmetrical
  • Momentary Close and Latch: 20,000 Amperes RMS Asymmetrical
  • Operation: Continuous 60 Hertz, 15 kV Nominal System Voltage, 95 kV BIL

Current interruption is achieved by three (one per phase) vacuum interrupter bottles which are supported at the top by a copper bus that is in turn isolated by insulators.

The contacts inside the vacuum bottles are operated when the main operating shaft is rotated, exerting a rotational force upon the bottles operating shaft. Upon release of the closing governor, the rotational force of the bottle operating shaft is transformed into a vertical force by the arm of the operating shaft. The force is in turn transmitted thru the wipe springs to the push rod assembly, closing the contacts inside the vacuum bottles.

The SMC line of Vacuum Load Break Switchs are assembled, adjusted and tested at the factory and is ready for installation. The SMC breaker is a rugged, reliable unit. However, reasonable caution should be exercised in the transportation and handling of the unit. The breaker should not be dropped, immersed, jolted, or otherwise subject to harsh treatment. If not abused, the SMC line of Vacuum Load Break Switchs will give thousands of reliable operations.

When a SMC Vacuum Load Break Switch is received,
a general damage inspection should be made. All parts should be visibly inspected for breakage with the special attention given to the vacuum bottles. A 19 kV (maximum) hipot test may be applied across the open interrupters if damage is suspected.

A mounting pattern of four (4) 1/2-inch diameter bolts in a 18 1/2 X 23-5/8 rectangular pattern is required. After the switch is securely mounted, it may then be wired using standard high and low voltage connection practices.

The operating handle comes supplied with one (1) woodruff key and two (2) 3/8-16 X 2 hex head bolts with nuts. The key is to be assembled to the operating shaft. Then tighten the hex bolts securely.