48results about How to "Eliminate residual magnetism" patented technology

The invention discloses a large-scale power transformer residual magnetism detection method. Comparison between curves of forward and reverse charging currents of a transformer is utilized to detect residual magnetism, whether there is residual magnetism is judged, and when a charging current is about 100 mA, the transformer without the residual magnetism is little affected; and after a forward and reverse charging test, current wave forms influenced by the residual magnetism is relatively visually represented, and whether there is residual magnetism is relatively visually represented. The transformer residual magnetism detection method has the technical effects that the universality is relatively good, the detection accuracy and effect are relatively good, and demagnetization is available.

A method for measuring DC resistances of transformer windings comprises the following steps of: 1, connecting an AB-phase test wire of a transformer to a degaussing machine, starting the degaussing machine, changing the wire to a BC phase after the AB phase is degaussed, and repeating the above steps till all residual magnetisms in an iron core of the transformer is eliminated; measuring the DC resistance Rac of a low-voltage side winding ac and the DC resistance RAO of a high-voltage side winding AO by using a magnetism optimization method through a DC resistance testing instrument, and repeating the step 1 to eliminate the residual magnetisms in the iron core of the transformer; measuring the DC resistance Rab of a low-voltage winding ab and the DC resistance RBO of a high-voltage side winding BO by using the magnetism optimization method through the DC resistance testing instrument, and repeating the step 1 to eliminate the residual magnetisms in the iron core of the transformer; and measuring the DC resistance Rca of a low-voltage winding ca and the DC resistance RCO of a high-voltage side winding CO by using the magnetism optimization method through the DC resistance testing instrument, and repeating the step 1 to eliminate the residual magnetisms in the iron core of the transformer. According to the method for measuring the DC resistances of the transformer windings, excessive magnetizing inrush current of the transformer no-load closing is avoided and the safety operation of the transformer is protected.

The invention relates to a Hall chip magnetic flux test device (1) for use in a SOT23 encapsulation test sorter, which is characterized in that the device (1) comprises a test support (9), a test seat (2) fixed on the upper end of the test support (9), a test clamp (3) which is arranged in the test seat (2) for holding a tested Hall chip, a plurality of gold fingers (5) electrically connected with the test clamp (3), a cover plate (6) positioned above the gold fingers (5) and a coil (4) wound on the test support (9), wherein the gold fingers (5) are fixed between the cover plate (6) and the test seat (2). The device can test the magnetic flux of the Hall chip in a SOT23 encapsulation test.

In one aspect, the invention provides a residual current device ( RCD ) for protecting a circuit by tripping in response to an imbalance signal representative of residual current imbalance in the circuit. The RCD trips the circuit when the imbalance signal exceeds a predetermined threshold rating. The RCD comprises test means for increasing the imbalance signal so as to test operation of the RCD against the rating. In another aspect the RCD comprises: a current transformer for generating an imbalance sense current in a sense coil in response to a current imbalance in an electric supply; and a degaussing coil for substantially removing remanence in the current transformer by application of a degaussing signal to the degaussing coil.

The invention provides a conical motor stop brake system; a conical motor rotates under the drive of a frequency changer; the system comprises a short-circuit control unit and a timer unit, wherein the timer unit is used for starting to time when the frequency changer stops outputting and outputting a first signal after a first time length is reached, and starting to time after an output end of the frequency changer is in short circuit and outputting a second signal after a second time length is reached; and the short circuit control unit is used for making two optional phases of the output end of the frequency changer in short circuit after receiving the first signal, and breaking the connection between the phase lines of the output end of the frequency changer after receiving the second signal. The invention also provides a corresponding method. Through making the phase lines of the output end of the frequency changer in short circuit when the conical motor is stopped, the residual magnetism in the conical motor can be eliminated rapidly, and thus the conical motor can close a brake rapidly.

The invention relates to workpiece demagnetizing equipment, in particular to a tunnel scanning pass-type demagnetizer. The tunnel scanning pass-type demagnetizer comprises a bed body and a control cabinet; the bed body comprises a base and a material loading bridge frame, wherein the material loading bridge frame is positioned above the base and is connected with the base end to end; a sports car is arranged on the base; the base is movably connected with the sports car; the upper part of the sports car is connected with an executive coil by adopting a supporting screw; and the sports car is also provided with a variable frequency motor. By the adoption of the tunnel scanning pass-type demagnetizer, the labor intensity of workers is lightened; the running speed of the sports car, the demagnetizing intensity and the waveform can all be adjusted; safe and efficient demagnetization can be realized; the quality of a workpiece is improved; and therefore, the service life of the workpiece is prolonged.

The invention discloses a permanent magnet synchronous motor diode follow current residual magnetism elimination device which comprises a driving module and a three-phase stator winding of a permanentmagnet synchronous motor, wherein the driving module is connected with the three-phase stator winding and used for starting and keeping the permanent magnet synchronous motor to normally run; the device is characterized by further comprising a demagnetization module and a control module used for forming a control signal; the demagnetization module is connected with the control module and the driving module, and based on the control signal generated by the control module, the demagnetization module eliminates residual magnetism in the three-phase stator winding through the driving module. According to the invention, the demagnetization module demagnetizes the residual magnetism in the permanent magnet synchronous motor based on the control signal of the control module, so that the influence of the residual magnetism on the shutdown and restart of the permanent magnet synchronous motor is avoided.

The invention provides a full-tube pulse demagnetization device and method, and the device comprises a demagnetization control unit and a demagnetization power supply; the demagnetization control unitis connected with a DC demagnetization switch and an AC demagnetization switch which are respectively used for switching on and switching off a DC demagnetization coil and an AC demagnetization coil;the demagnetization power supply comprises a demagnetization alternating-current power supply and a demagnetization direct-current power supply which are used for supplying power to the alternating-current demagnetization coil and the direct-current demagnetization coil respectively, and the central axis of the direct-current demagnetization coil and the central axis of the alternating-current demagnetization coil are located on the same horizontal line; the number of turns of the direct-current demagnetizing coil is gradually reduced from one end far away from the alternating-current demagnetizing coil to one end close to the alternating-current demagnetizing coil. The demagnetizing device is convenient to use, good in demagnetizing effect and capable of meeting the online use requirement.

MR imaging method, residual magnetizaton amount measuring method and MRI apparatus are disclosed. To suppress the influence of remanent magnetization caused by a previous pulse sequence for MR imaging to an MR image, Gradient pulse strings RS1 to RS4 for degaussing are applied, preceeding the pulse sequence for MR imaging in order to cancel remanent magnetization caused by a previous pulse sequence for MR imaging.

The invention relates to a control method and circuit for engagement and disengagement of a DC circuit breaker and belongs to the technical field of DC circuit breaker control. According to the invention, current in a direction reverse to that of a main circuit of an engagement coil is applied to two ends of the engagement coil, so that reverse charging is performed on the engagement coil, residual magnetism of iron core material of the engagement coil is eliminated, the disengagement speed of the engagement coil is improved, so that a guarantee is provided for quick disengagement.

The invention discloses an emergency stop device of a transformer substation hot-line work robot, selects a composite button, and provides a new method for wiring in a failure safety mode. Two pairs of normally closed contacts are connected to the positive electrode end of a power supply in series, and two pairs of normally open contacts are connected to the negative electrode end of the power supply in parallel; the method comprises the following steps of: converting circuit connection by utilizing a composite button, connecting a coil, a diode, a capacitor and a resistor of the direct current contactor in parallel to form an RLC parallel oscillating circuit, pressing the composite button in an emergency state, disconnecting a normally closed contact, and enabling current flowing through the coil to form a path through the diode so as to eliminate residual magnetism of the iron core of the direct current contactor. Overvoltage caused by coil current abrupt change is prevented; when the direct-current contactor is started, the normally open contact is closed, the direct-current contactor coil, the diode, the capacitor and the resistor are connected in parallel to form an RLC parallel oscillation circuit, oscillation current is generated, residual magnetism of the iron core of the direct-current contactor is eliminated in time, and therefore the technical problems that in the prior art, reliability is poor, and quick-action performance is poor are solved.

An on-load voltage and capacitance regulation transformer comprises a tap switch and other components. The tap switch is composed of three operating mechanisms, three capacitance regulation switches and two voltage regulation switches. Each operating mechanism is provided with a bistable permanent magnet assembly and a poking rod of the bistable permanent magnet assembly. Each switch comprises a sealed vacuum insulating cylinder. All switching surfaces of movable contact pieces and static contact pieces are located inside vacuum cylinder cavities of the insulating cylinders. The width of the switching surfaces of the high-voltage side static contact pieces in the three capacitance regulation switches is smaller than the width of the switching surfaces of the low-voltage side static contact pieces in the three capacitance regulation switches. Due to the fact that the switching surfaces of the movable and static contact pieces are located inside the vacuum cylinder cavities, the on-load voltage and capacitance regulation transformer has the advantages that arc extinguishing performance is reliable, the service life is long and transformer oil is not polluted by electric arcs; in addition, after the technology that a high-voltage winding and a low-voltage winding are cut off in sequence, and the low-voltage winding and the high-voltage winding are connected in sequence is adopted, the small electric arcs are obtained, residual magnetism inside an iron core of the transformer is eliminated, inrush current and overvoltage formed when the high-voltage winding is connected again are avoided, and the voltage fluctuation amplitude in the switching process is effectively reduced.