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183results about How to "Reduce asymmetry" patented technology

Load control circuit and method for achieving reduced acoustic noise

A load control circuit having first and second terminals for connection in series with a controlled load comprises a bidirectional semiconductor switch for switching at least a portion of both positive and negative half cycles of an alternating current source waveform to the load. The bidirectional semiconductor switch has a control electrode. The load control circuit includes a phase angle setting circuit, including a timing circuit, which sets the phase angle during each half cycle of the AC source waveform when the bidirectional semiconductor switch conducts. The phase angle setting circuit includes a voltage threshold trigger device connected in series with the control electrode of the switch. The phase angle setting circuit further comprises a rectifier bridge connected in series between an output of the timing circuit and the control electrode of the semiconductor switch, wherein the rectifier bridge has a first pair of terminals and a second pair of terminals, the first pair of terminals connected in series between an output of the timing circuit and the control electrode of the semiconductor switch, and the second pair of terminals connected to the voltage threshold trigger device. The load control circuit further includes an impedance in series electrical connection with the semiconductor switch control electrode. Acoustic noise generated in the load connected in series with the load control circuit is reduced, particularly when the load is a toroidal transformer driving a magnetic low voltage lamp and the load control circuit is a two-wire dimmer.
Owner:LUTRON TECH CO LLC

Automatic intelligent power distribution system and power distribution method

The invention discloses an automatic intelligent power distribution system and a power distribution method. The power distribution system comprises a power distribution executing unit, and the power distribution executing unit receives a power distribution command from a power distribution monitoring terminal and gates a corresponding phase line on a three-phase power transmission line to a single-phase power supply line on an output side of the power distribution executing unit to achieve intelligent power distribution. According to the automatic intelligent power distribution system, low-voltage three-phase disequilibrium distribution on an input side of a single-phase user is achieved through the power distribution executing unit on an input side of an electricity meter of the single-phase user, the power distribution monitoring terminal receives the electrical load information of each single-phase user in a wireless or power line carrier communication mode, and a basis is provided for the equilibrium distribution of single-phase user quantity on each phase line of the three-phase power transmission line on the whole; the power distribution monitoring terminal sends the power distribution command to the power distribution executing unit and the power distribution executing unit enables each single-phase user to be connected to a corresponding power supply phase line in a grouping mode, and therefore equilibrium power distribution is achieved for single-phase users on a low-voltage side.
Owner:长沙高升电子电器科技有限公司

Self-maintained friction stir welding method with reversely rotating upper and lower shaft shoulders

InactiveCN101979209AReduced fracture tendencyReduce torque actionNon-electric welding apparatusEngineeringMechanical engineering
The invention discloses a self-maintained friction stir welding method with reversely rotating upper and lower shaft shoulders, and relates to a self-maintained friction stir welding method to solve the problems that: the upper and lower shaft shoulders have unequal diameters but rotate in the same direction with equal speed, and in the welding process, the weld heat input is large, a workpiece is easy to deform, a mixing needle is inclined to fracture, and the distribution of a weld zone temperature field, a joint structure and residual stress are asymmetric, so that the joint performance is asymmetric, and the bearing capacity of a welding structure is reduced. The method comprises the following steps of: 1, determining the size of a stirring head, namely determining the diameter of the upper shaft shoulder, the stirring needle and the lower shaft shoulder according to the thickness of a first welded workpiece and a second welded workpiece; 2, determining the use length of the stirring needle; 3, fixing the first welded workpiece and the second welded workpiece; 4, positioning the stirring head; and 5, performing friction stir welding on the first welded workpiece and the second welded workpiece, namely integrally forming the upper shaft shoulder and the stirring needle, and allowing the lower shaft shoulder and the upper shaft shoulder to rotate in opposite directions. The self-maintained friction stir welding method is used for self-maintained friction stir welding.
Owner:HARBIN INST OF TECH

Load control circuit and method for achieving reduced acoustic noise

A load control circuit having first and second terminals for connection in series with a controlled load comprises a bidirectional semiconductor switch for switching at least a portion of both positive and negative half cycles of an alternating current source waveform to the load. The bidirectional semiconductor switch has a control electrode. The load control circuit includes a phase angle setting circuit, including a timing circuit, which sets the phase angle during each half cycle of the AC source waveform when the bidirectional semiconductor switch conducts. The phase angle setting circuit includes a voltage threshold trigger device connected in series with the control electrode of the switch. The phase angle setting circuit further comprises a rectifier bridge connected in series between an output of the timing circuit and the control electrode of the semiconductor switch, wherein the rectifier bridge has a first pair of terminals and a second pair of terminals, the first pair of terminals connected in series between an output of the timing circuit and the control electrode of the semiconductor switch, and the second pair of terminals connected to the voltage threshold trigger device. The load control circuit further includes an impedance in series electrical connection with the semiconductor switch control electrode. Acoustic noise generated in the load connected in series with the load control circuit is reduced, particularly when the load is a toroidal transformer driving a magnetic low voltage lamp and the load control circuit is a two-wire dimmer.
Owner:LUTRON TECH CO LLC

Inhibition method for three-phase imbalance voltages of power distribution network

The invention discloses an inhibition method for three-phase imbalance voltages of a power distribution network. The method includes the following steps: installing a controllable current source between a neutral point of the power distribution network and the ground; measuring three-phase voltages and a neutral-point displacement voltage of the power distribution network in a real-time manner; when the displacement voltage is larger than 5% of a rated phase voltage, identifying whether the operation state of the power distribution network is a three-phase imbalance state; and under a condition of the three-phase imbalance state of the power distribution network, injecting a power frequency current I <*> to the power distribution network through the controllable current source and searching for an optimal injection current phase and amplitude and inhibiting the neutral-point displacement voltage to be zero. The method uses the neutral-point displacement voltage as a control target and forces the neutral-point displacement voltage to be zero through injection of the current to the power distribution network so that neutral-point displacement overvoltage caused by asymmetry of three-phase to-ground parameters of the power distribution network is eliminated completely and thus inhibition of three-phase imbalance overvoltages of the power distribution network is realized.
Owner:ELECTRIC POWER RES INST OF GUANGDONG POWER GRID

Condenser with liquid separation type spiral tube structure

The invention discloses a condenser with a liquid separation type spiral tube structure, which belongs to the technical fields of heat exchange and heat transfer. A spiral heat exchange tube is fixed in a shell of the condenser with the liquid separation type spiral tube structure; a liquid guiding tube is distributed on the outer circumference of the spiral heat exchange tube; the upper end of the spiral heat exchange tube is a condensing working substance inlet tube; the lower end of the spiral heat exchange tube is a condensing working substance outlet tube; the upper end of the outer circumference of the shell is a cooling water outlet; and the lower end of the outer circumference of the shell is a cooling water inlet. In a condensing process, a thick liquid film distributed on the side wall surface of the spiral outer circumference is derived in a non-dynamical way by utilizing the combined action of surface tension, capillary force and centrifugal force; a thin liquid film is promoted to transfer heat in a condensation phase change process; and the heat resistance of a condensed liquid film on the side of the outer circumference of a spiral tube is decreased, thereby obviously improving the heat exchange performance on the side of a condensation phase change tube. By using the condenser with the liquid separation type efficient spiral tube, a condensate liquid is separated mainly by means of the centrifugal force and the capillary force without being influenced by gravity, and the condensation heat exchange coefficient can be obviously improved both in a ground environment or a microgravity environment.
Owner:NORTH CHINA ELECTRIC POWER UNIV (BAODING)

Emergency supply unit with a ram-air turbine adapted to be driven by an air stream and with an energy converter for aircraft

The invention relates to an emergency supply unit (1) with a ram-air turbine (2) which can be driven by an air stream (14) and with an energy converter (4) for at least partly maintaining the functioning of a hydraulic system and/or electrical system on board an aircraft in an emergency situation, wherein the energy converter (4) can be driven by means of the ram-air turbine (2) and the emergency supply unit (1) can selectively be brought into a standby mode or into an operating mode.; According to the invention, at least the ram-air turbine (2) is surrounded substantially concentrically by a casing (5) forming a flow channel (6) and the energy converter (4) is directly coupled to the ram-air turbine (2) via a drive shaft (3) and the air stream (14) can be delivered to the ram-air turbine (2) through at least one air inlet (9, 17, 18), wherein the spatial position of the ram-air turbine (2) remains substantially unchanged when changing between the standby mode and the operating mode. The integration of the ram-air turbine (2) into the flow channel (6) results in a very compact and space-saving design of the emergency supply unit (1) according to the invention, thus offering a plurality of additional installation options, for example in the region of the landing flap rail covering (8) below a wing (7) of an aircraft.; Moreover, the substantially completely encapsulated formation of the emergency supply unit (1) without a pivot arm and with direct coupling of the ram-air turbine (2) to the energy converter (4) through the drive shaft (3) is structurally simple and therefore permits largely maintenance-free operation with greater fail safety.
Owner:AIRBUS OPERATIONS GMBH

Online automatic power distribution method and device

ActiveCN103997051AHigh practicability and computing efficiencyReduce three-phase load asymmetryPolyphase network asymmetry elimination/reductionPolyphase network asymmetry reductionSingle phaseSupply & distribution
The invention discloses an online automatic power distribution method and device. The method comprises the steps that a first voltage value corresponding to a phase-A line in a three-phase electric transmission line, a second voltage value corresponding to a phase-B line in the three-phase electric transmission line, a third voltage value corresponding to a phase-C line in the three-phase electric transmission line and a fourth voltage value corresponding to a power supply line of a single-phase user are collected; the first voltage value, the second voltage value and the third voltage value are compared with one another, and the largest voltage value is determined; the difference value of the largest voltage value and the fourth voltage value is calculated, and whether the difference value is zero or not is judged; if the different value is zero, no power distribution instructions are generated, and the original power distribution state is kept; if the difference value is not zero, a power supply of the single-phase user is switched to the phase line corresponding to the largest voltage value. According to the online automatic power distribution method and device, power utilization balance on the three-phase branch circuit can be ensured to the maximum through the power supply distribution strategy, practicability and computational efficiency are high, the three-phase load dissymmetry can be reduced to the maximum, low-voltage electric transmission side line damage is reduced, and power supply safety, reliability and efficiency are improved.
Owner:长沙高升电子电器科技有限公司

Friction stir welding method for reversely rotating stirring needle and shaft shoulder

The invention discloses a friction stir welding method for reversely rotating a stirring needle and a shaft shoulder, relates to a friction stir welding method, and solves the problems that the conventional friction stir welding method has asymmetrical temperature field, joint structure and residual stress distribution so as to cause asymmetrical joint performance and reduce the bearing capacity of the welding structure. A first welded workpiece and a second welded workpiece are butted and clamped on a working table; the stirring needle pricks a part to be welded at the rotating speed of 100 to 3,000 revolutions per minute; the rotating direction of the shaft shoulder of the stirring head is opposite to that of the stirring needle, and the rotating speed of the shaft shoulder of the stirring head is the same as that of the stirring needle; and when reaching the set pricking depth, the stirring head moves along the weld joint direction at a speed of 100 to 5,000 mm per minute. The directions of driving forces of the stirring needle and the shaft shoulder on the flowing welded materials are opposite, the asymmetry of the friction stir welding head structure and performance is reduced, and the mechanical property of the friction stir welding joint is improved.
Owner:HARBIN INST OF TECH
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