Abstract: The system provides for one or more photovoltaic panels (3) or other energy sources, connected to a series of inverters (5) in parallel, the outputs of which are connected to a load (Z) and/or to an electricity distribution grid (7). One of the inverters operates as master unit and generates a power control signal in order to track the maximum power point that can be obtained from the panels (3). The other inverters operate as slave units. The control is performed so that all the inverters absorb a variable quantity of power according to the fluctuations in the power available at the output of the photovoltaic panels (3) or other source subject to fluctuations.

Abstract: A method of controlling an inverter to includes determining the components of a phasor representing the output current from the inverter in a fixed reference system; determining the components of the current phasor in a reference system rotating at a velocity equal to the velocity of rotation of the phasor representing the grid voltage; and comparing the components of the current phasor in the rotating reference system with a reference, again expressed in the rotating reference system, to determine an error signal, by means of which the inverter is controlled.

Abstract: An overhead door, which is adapted to have its primary tracking members temporarily disengaged from their primary track when impacted by a substantial force when in the closed or partially closed position, is adapted to smoothly transition from its vertical, closed position to a non-vertical, open position by the use of second tracking members and track which come into use as the door panels transition from a vertical orientation to a non-vertical orientation. The impact caused disengagement feature is therefore effective without interference from the second tracking members, but progressively gives way to the second tracking members and track as the door is raised toward an open position.

Abstract: The bottom surface of a dock leveler is insulated by attaching sheets of insulative material between adjacent support beams. Attachment is by way of magnet attached to the bottom surface of the deck to hold downwardly projecting spikes that penetrate the insulative material, with a self locking washer then being placed over the spike in order to secure the sheet of material in place. Installation with variable widths between adjacent support beams is facilitated by pre-perforating the sheets of insulative material along longitudinal lines to thereby allow easy separation and width adjustment to match the variable widths between the support beams.

Abstract: A temporary barrier chain for a loading dock door opening includes a vertical orientated storage tube on one side of the opening and a retainer on the other side thereof, and a counterweighted chain extending from inside the storage tube to a retainer on the other side of the opening, with the chain being comprised, at least partially, of successively lighter weight sections toward the retainer end such that the combined weight of the counterweight and suspended chain within the storage tube will cause the chain to be automatically retrieved into the storage tube when released from the retainer.

Abstract: A method of controlling an inverter to includes determining the components of a phasor representing the output current from the inverter in a fixed reference system; determining the components of the current phasor in a reference system rotating at a velocity equal to the velocity of rotation of the phasor representing the grid voltage; and comparing the components of the current phasor in the rotating reference system with a reference, again expressed in the rotating reference system, to determine an error signal, by means of which the inverter is controlled.

Abstract: An emergency power generating unit (2), comprising a gas turbine (23) to supply a train on-board systems in the event of a failure of the main electrical power supply. Specifically the power generated by the turbine is used to run an electrical energy generator (29) for powering an air conditioning system (77).

Abstract: A laminar flow air mover includes a cylindrical fan having an outlet opening connected to a conduit system. The conduit system includes a first portion connected to the outlet portion of said centrifugal fan and an outlet portion detachably connected to the first portion by a reusable breakaway connection. A baffle plate is pivotably mounted in the outlet of said outlet portion and extends transversely of said outlet portion to direct a coherent flow of air for a substantial distance in the desired direction.

Abstract: A circuit for controlling the power supply voltage of an electric motor includes means for detecting the difference between a mains voltage and a reference voltage, and means for generating alternating correction voltage whose frequency is equal to the frequency of the mains voltage and which is phase-shifted with respect to the mains. The phase shift between the mains voltage and the correction voltage is proportional to the between the mains voltage and the reference voltage, and the correction voltage is added to the mains voltage.

Abstract: A laminar flow air mover includes a cylindrical fan having an outlet opening connected to a conduit system. The conduit system includes a first portion connected to the outlet portion of said centrifugal fan and an outlet portion detachably connected to the first portion by a reusable breakaway connection. A baffle plate is pivotably mounted in the outlet of said outlet portion and extends transversely of said outlet portion to direct a coherent flow of air for a substantial distance in the desired direction.

Abstract: A controllable electrical switch having a power system and switching device for connecting a source voltage to a load. The power system includes a switching regulator to extract energy directly off the non filtered full wave rectified input voltage to minimize the average magnitude of the current when the switching device is in the off-state. For on-state power the controllable electrical switch may include a transformer connected in series with the switching device. The controllable electrical switch and power system may be used to replace a standard two- wire or three-wire wall switch, and may be used over a wide voltage and load power range in a low cost, small package with low power dissipation.

Abstract: A power supply circuit for discharge lamps having a load circuit with at least one discharge lamp and controlled switches with a switching control means which control the opening and closing of the switches to supply the load circuit with a high-frequency alternating signal. A recognition circuit, which recognizes the type of lamp connected to the load circuit by the power rating of the lamp, is provided. Control means which modify the switching conditions of the switches according to the type of lamp connected to the load circuit are also provided.