Abstract: A method of monitoring a refrigeration unit including detecting premature return of air discharged into a conditioned space, and distinguishing this "short cycling" problem from a refrigeration capacity problem. The method includes determining the rates of change of the temperatures DA and RA of the discharge air and return air, respectively, during temperature pull down of the conditioned space, and comparing the rates of change with predetermined constants selected to detect a short cycling of the discharge air. When the rates of change do not fit a normal temperature pull down, the differential .DELTA.D between the temperatures DA and RA of the discharge air and return air is determined and compared with a third constant. Predetermined results of the comparisons of the rates of changes of DA and RA, and the temperature difference .DELTA.

Abstract: A method of operating a refrigeration system having a compressor driven by an engine, with the refrigeration system being operable in a first control mode to hold the temperature of a conditioned space at a selected set point temperature, and in a second control mode to maintain the engine in a ready-to-start condition. The second control mode includes monitoring the ambient temperature, and determining a dynamic set point temperature as a function of ambient temperature. The engine is started and stopped to maintain engine startability, and also as a function of the dynamic set point temperature, to maintain the temperature of the conditioned space at the dynamic set point temperature while maintaining the engine in a ready-to-start condition. Control is changed from the second to the first control mode, when a programmed start feature is activated, with the time of such mode change being a function of the difference between the ambient temperature and the selected set point temperature.

Abstract: A spring charging mechanism for electrical circuit breakers and transfer switches of the type in which a spring is charged by rotation of a shaft. The charging mechanism has a charging shaft with two independently operating ratchet mechanisms coupled thereto. One ratchet mechanism may be driven by hand while the other may be separately motor-driven or held stationary by a bracket. The ratchet mechanism which is not in operation acts as a locking device which prevents rotation of the charging shaft in the discharge direction while allowing rotation in the charging direction. The charging mechanism is adaptable for either hand or motor-driven operation or both. It also features an inexpensive and easily-installed flexible, resilient, insulating sleeve which insulates the charging mechanism from the operator, and a key arrangement for coupling a handle to a ratchet mechanism which distributes stress within the handle and protects the handle fastening screws from destructive shear stresses.

Abstract: A hybrid monolithic IC that is standardized for controlling various types of electrical equipment, such as circuit breakers, motor controllers and the like. The IC is a hybrid monolithic IC, fabricated in CMOS technology, The shortcomings of utilizing CMOS technology for linear or analog circuitry is overcome by the implementation of the IC to provide a monolithic IC that is relatively less expensive than using multiple ICs or a single IC fabricated from biCMOS technology.

Abstract: A molded case circuit breaker includes an interlock which prevents the operating handle from being placed in the off position after the main contacts have been welded together. By preventing the operating handle from being placed in an off position during such a condition, the operating handle will indicate the correct status of the main contacts and the operator will be made aware that the main contacts are welded together.

Abstract: Methods and apparatus for controlling the temperature of a conditioned space, including a supply of cryogen, and a fluid flow path for the cryogen which includes a heat exchanger. A heater is disposed to heat cryogen in the flow path in response to predetermined conditions, and a cryogen pre-heater is disposed to aid the heater. In a first embodiment, the pre-heater is aided by directing warm cryogen in heat exchange relation with cryogen flowing through the pre-heater, with the warm cryogen being taken from a point downstream from the heat exchanger. In another embodiment, the heater generates heated gases as a by-product, with the pre-heater being aided by directing the heated gases in heat exchange relation with cryogen flowing through the pre-heater.

Abstract: Methods and apparatus for controlling the temperature of a conditioned space to a predetermined set point temperature, utilizing a supply of cryogen in liquid and vapor states. The two states are drawn from the supply in two separate flow paths. The liquid cryogen is vaporized in a heat exchanger, and the two flow paths are then combined. The combined cryogen is used to drive a vapor motor connected to a fan, with the fan moving air between the conditioned space and the heat exchanger. Heat is applied to the cryogen as required to hold the set point temperature or to defrost the heat exchanger. In a preferred embodiment, the cryogen is added to a first vessel at the pressure provided by ground support apparatus, and expanded into a second vessel as a function of system conditions, to provide the supply of cryogen in both the liquid and vapor states.

Abstract: Apparatus for protecting a synchronous generator from under-excitation, includes a limiter implemented as part of a microprocessor based voltage regulator. The limiter selectively characterizes one or more limiting parameters, such as, system stability, machine capability and loss of field protection, as straight line segments in the real/reactive power plane to provide versatile, easily modified limits on excitation.

Abstract: A molded case circuit breaker having current limiting capabilities is dimensionally optimized for relatively smaller frame size circuit breakers. The handle yoke is supported with rollers thereby allowing the crossbar to be disposed in the space normally utilized for the handle yoke pivot axis. A clinch joint arcer assembly with a plurality of arcing contact arms, each pivotally connected by a clinch joint to a pivotally mounted main contact arm permits additional main contact arms to be provided in the same space normally occupied by the arcing contact arms alone. Additionally, arcing contact spring housings protect the arcing contact springs from deterioration due to corrosive ionizing gases generated during interruption. A positive off link assembly prevents the operating handle from being placed on an OFF position when the main contacts are welded together and transfers the force applied to the operating handle to the upper link to allow the weld to be broken.

Abstract: A refrigeration system associated with a conditioned space to be controlled to a predetermined set point temperature via heating and cooling cycles. The refrigeration system includes a heat exchanger, air mover apparatus disposed to circulate air between the conditioned space and the heat exchanger, cryogenic cooling apparatus which includes a combustible fuel in a cryogenic state, and heating apparatus. The cryogenic characteristic of the fuel is utilized to implement the cooling cycle, and the combustible characteristic of the fuel is utilized by the heating apparatus to implement the heating cycle. In preferred embodiments of the invention an internal combustion engine is associated with the refrigeration system, and the air mover means includes a vapor motor, with the cryogenic fuel being vaporized and then expanded in the vapor motor to drive same, and with the expanded vaporized fuel operating the internal combustion engine.

Abstract: A multiple-pole ground fault interrupter, enclosed in an insulated housing, formed with multiple compartments, includes ground fault detection circuitry for detecting ground fault current that can be a personnel hazard. The ground fault interrupter includes a single trip solenoid assembly having multiple windings, each winding corresponding to one of the poles. The trip solenoid is mounted on a printed circuit board and electrically connected to the ground fault detection circuitry disposed thereon. The printed circuit board together with the trip solenoid assembly is disposed in a single compartment which reduces the amount of interconnection wiring between compartments, which, in turn, results in a reduced cost to manufacture the device. The use of a single trip solenoid assembly also results in the use of less components which further reduces the cost of manufacturing the device.

Abstract: An electromagnetic clutch, including a contact plate assembly, a rotor adapted for connection to a driven device, and first mounting assembly for mounting the contact plate assembly to a rotatable member associated with a driving device. The first mounting assembly includes compression springs for biasing the contact plate assembly away from the rotor. An electromagnetic assembly overcomes the bias of the compression springs when energized, causing the contact plate assembly to engage the rotor. The first mounting assembly includes resiliently mounted members which allow the contact plate assembly to oscillate circumferentially relative to the rotatable member, in response to torsional oscillations in the driving device. A second mounting assembly mounts each of the compression springs between the rotatable member and the contact plate assembly, isolating the compression springs from damage due to relative circumferential movement between the rotatable member and contact plate assembly.

Abstract: Process and apparatus for calibrating an electrical device such as a circuit breaker, motor controller or monitor is taught. A precision power supply device is interconnected by way of appropriate input channels to the device to be calibrated for supplying a precise accurate calibration variable as an input. A personal computer is interlinked by way of a communications network with the apparatus to be calibrated and is also interlinked with the precision supply device so that the personal computer has available the exact value of input variable utilized.

Abstract: Methods of monitoring the operation of a refrigeration system, including interlocking the selection and operation of an engine and electric motor which are arranged to alternatively function as prime movers for a refrigerant compressor; detecting slippage of a clutch connected between the engine and compressor; and, detecting improper rotational direction of an evaporator fan motor. The interlocking method prevents energization of the drive motor while the engine is operative, and it includes monitoring engine oil pressure and engine RPM. The clutch slippage method includes detecting engine speed fluctuations and the polarity of battery current. The monitoring of the evaporator fan motor, which drives a fan which draws return air RA from a conditioned space, and discharges conditioned air DA into the conditioned space, includes the steps of comparing the difference between the temperatures RA and DA of the return air and discharge air with a predetermined reference value.

Abstract: An oil flooded screw compressor including suction, rotor, and discharge sections having suction, intermediate pressure, and discharge ports, respectively, and an oil sump. The discharge section includes radially spaced internal and external housings, with the internal housing receiving an oil-gas stream from the rotor section. A filter is disposed to surround the internal housing, with the filter including a cylindrical, foraminate body portion, an end wall, and a filter pad against the end wall. The oil-gas stream from the rotor section exits the inner housing, via an opening which forms part of a first stage of oil removal. The oil-gas stream strikes the filter pad, removing oil as the oil-gas stream is forced to turn 90 degrees to exit the filter through the foraminate body portion, which also removes oil. The filter functions as second and third stages of oil removal.

Abstract: An E shaped stationary magnet/moveable armature combination for use in an electromagnetic contactor. The magnet has three legs; two outer legs and an inner leg. The armature can be a single, essentially rectangular bar or have three legs corresponding to the legs of the magnet. The moveable armature is caused to contact the magnet by a magnetic field created when electrical current is applied to a current carrying coil. An outer leg of the magnet and/or armature is arranged such that an air gap remains between an outer leg of the magnet and armature. The provision of an air gap in an outer leg reduces noise emitted from the electromagnet.

Abstract: A heated accumulator for a refrigeration system includes a cylindrical tank closed by upper and lower tank caps. The tank is divided into upper and lower chambers by a plate disposed near the upper tank cap, with the lower chamber defining a sump. The plate includes a central opening surrounded by smaller openings. An outlet U-tube has a first end disposed within the central opening of the plate, a second end which extends through the upper tank cap, and a central portion which extends into the sump. A refrigerant inlet tube includes swirl ports which direct refrigerant into a vortex against the inner surface of an upper portion of the tank. Heat is applied to this same upper tank portion, introducing heat directly into the swirling liquid refrigerant. Refrigerant vaporized by the heat rises into the upper tank chamber where it is drawn by compressor suction into the outlet U-tube.

Abstract: A refrigeration system of the type having an economizer cycle is provided with a null cycle, in addition to heating and cooling cycles, without shutting a compressor prime mover down, to preserve air flow in a conditioned space. First, second and third controllable valves respectively: (1) select main and auxiliary condensers, (2) open and close a liquid line, and (3) open and close a line which provides a warm liquid to an economizer heat exchanger. The valves are controlled in at least one predetermined open/close pattern during a null cycle, and preferably in a plurality of selectable predetermined open/close patterns, to provide a null cycle at any instant which substantially matches the net heat gain or loss taking place in the conditioned space. Thus, the temperature of the served space will be more apt to remain in a null temperature range close to set point, providing smoother and more accurate control over the temperature of the conditioned space for longer shelf life of perishables stored therein.