Abstract: A circuit breaker switchgear housing device having a stab positioning system whereby a draw-out circuit breaker having separable contacts is contained in the switchgear housing. A stab positioning system is utilized so as to precisely locate stabs so that a circuit breaker having contact clusters which are electrically attached to the circuit breaker contacts make accurate and uniform contact with the stabs. The stabs are generally a rectangular-shaped bar with one of the ends being rounded off. Cut into two sides of the stab and opposing each other are notches. The stab is inserted into a retainer or positioning washer which has a bayonet-type lock opening into which the stab is inserted and rotated 90.degree., thereby prohibiting axial movement of the stab with respect to the washer. A retainer or positioning washer having an opening slightly larger than the stab cross-section is used to rigidly position an inserted stab, prohibiting rotational movement with respect to the opening in the stab.

Abstract: There is provided by this invention a novel switchgear shutter design employing curvilinear displaced shutter means which provide an entirely metallic grounded surface between the potentially live contacts and the front of the compartments. This novel shutter means is disposed to move to a safe and effective distance away from live electrical ports when the circuit breaker is moved into its normal operating position.

Abstract: A grounding arrangement for a shutter for a high voltage metal clad switchgear arrangement is taught. The shutter is a composite of an electrically insulating material such as polyester and islands of electrically conductive material such as non-magnetic aluminum. The polyester material reduces the chance for flash-over between the high voltage conductors and the grounded metal islands or other conductors, while the grounded metal islands provide a region of zero ground potential in an area associated with the openings of the high voltage terminal assemblies to thus assure that personnel who approach this region will always be exposed to ground potential and not high voltage potential. When the shutter is raised, a dual switching arrangement is automatically actuated to disconnect the islands of the shutter from the ground potential of the metal clad switchgear.

Abstract: A shutter for high voltage metal clad switchgear is taught which is a composite of electrically insulating material such as polyester and islands of electrically conductive material such as non-magnetic aluminum. The polyester material reduces the chance for flash-over between the high voltage conductors and the grounded metal islands or other conductors, while the grounded metal islands provide a region of zero ground potential in an area associated with the opening in high voltage terminal assemblies to thus assure that personnel who approach this region will always be exposed to ground potential and not high voltage potential.

Abstract: The heat pump system includes a first and a second centrifugal compressor arranged in series relation in a system including interstage expansion of the refrigerant. A pair of parallel circuits is provided for controlling the energization of the compressors in a sequence in which the first to start compressor must be energized to obtain completion of the second parallel circuit required for energization of the second to start compressor. The start of the second compressor is delayed for a period permitting the first compressor to come up to speed and the first circuit controlling the energization of the first compressor will be interrupted unless the second compressor has started within a short period of time after the time delay in starting the second compressor.