91 results about "Residual flux" patented technology

To suppress the magnetizing inrush current occurring when supplying power of three phases of the transformer are performed simultaneously using three single-phase circuit breakers or a non-phase segregated operation-type circuit breaker, without providing a circuit breaker with a resistor or other equipment. A magnetizing inrush current suppression method for transformer suppresses a magnetizing inrush current occurring at the start of energizing of a three-phase transformer 300, when a three-phase power supply 100 is input to a terminal of each phase by means of a three-phase circuit breaker 200. In the method, by integrating phase voltages or line-to-line voltages on the primary side or the secondary side or the tertiary side when three-phase AC voltages are applied in a steady state to the transformer 300, steady-state magnetic flux 4, 5, 6 for each phase of the transformer is calculated, and the polarity and magnitude of the residual magnetic flux 7, 8, 9 of each phase of the transformer after the circuit breaker 200 shuts off the transformer are calculated, and the three-phase circuit breaker is caused to close simultaneously in a region 13 in which three phases overlap, each of the three phases having the polarity of the steady-state magnetic flux 4, 5, 6 equal to the polarity of the residual magnetic flux 7, 8, 9 for each phase of the transformer.

To provide a magnetizing inrush current suppression device for transformer and control method of same, which accurately calculates the residual magnetic flux when a transformer installed in a non-solidly earthed system, is interrupted by circuit breakers, and which enables suppression of the magnetizing inrush current occurring when three single-phase circuit breakers or single-phase circuit breakers are used for simultaneously supplying power to three phases of the transformer, without providing a circuit breaker with a resistor or other equipment to enlarge the circuit breaker. The device has steady-state magnetic flux calculation means for calculating the line-to-line steady-state magnetic flux of three-phase power supplies, residual magnetic flux calculation means for calculating the primary line-to-line residual magnetic flux of the transformer when the circuit breakers interrupt the transformer, phase detection means for detecting a phase at which the polarity and magnitude of the calculated steady-state magnetic flux and residual magnetic flux coincide for each line-to-line. Closing control means firstly causes only two-phase of the circuit breakers, which are connected with the line-to-line, to close at the detected phase, and then causes the remaining one-phase circuit breaker to close.

A closing phase that produces the smallest energization flux error at a connection input point is calculated based upon a residual flux of the first closing phase and the preliminarily given pre-arc characteristic and closing time deviation characteristic of a three-phase circuit breaker, so that the calculated phase value is set as a target closing phase of the first closing phase. A closing phase that produces the smallest energization flux error when a residual flux of zero is calculated, so that the calculated phase value is set as a target closing phase of the remaining two phases. The total time required from the reference point to the target closing phases of the remaining two phases and a delay time corresponding to an integer multiple of a given cycle of the three-phase power supply is set as a target closing time of the remaining two phases.

The invention discloses a transformer remanence detection and demagnetization method which comprises the following steps: collecting residual flux content of a test transformer, and inputting the residual flux content into an intelligent analysis system; reading the residual flux content of the test transformer through a human-computer interaction interface, and inputting corresponding control instructions; controlling the output of a frequency conversion voltage-regulating unit through the control instructions; and outputting by the frequency conversion voltage-regulating unit a low-frequency AC voltage required for demagnetization, and carrying out demagnetization on the test transformer. The invention also discloses a transformer remanence detection and demagnetization device which comprises an AC power supply module, a power supply conversion module, a DC power supply module, a control acquisition module, the frequency conversion voltage-regulating unit, a man-machine interaction unit, a data acquisition module, the intelligent analysis system and the test transformer. The low-frequency AC voltage is utilized for demagnetization, thereby reducing power capacity and size of the demagnetization device; and through the man-machine interaction unit, operation personnel can obtain the demagnetization processing progress accurately and visually, and input the corresponding control instructions, thereby realizing thorough demagnetization of the test transformer.

The invention discloses a transformer operation control apparatus and method for suppressing magnetizing inrush current. A control portion 80 for a breaker 10 causes the breaker 10 to apply a current of a first apply phase (R phase) at a timing where a residual flux of R phase agrees with a steady magnetic flux. Thereafter, the control portion 80 determines whether or not the current measured by current measuring portions 40R, 40S, 40T exceeds a threshold value. When the measured current does not exceed the threshold value, the control portion 80 causes the breaker 10 to apply currents of the other two phases (S and T phases) at a timing where a voltage of R phase becomes zero. When the measured current exceeds the threshold value, the control portion 80 causes the breaker 10 to once shut off the current of R phase and to apply again the current of R phase.

Inrush current suppression apparatus for suppressing a transformer inrush current including a transformer side voltage measurement unit which measures a voltage at a side of a transformer, a residual magnetic flux calculation unit which calculates three line-to-line residual magnetic fluxes, a power supply side voltage measurement unit which measures a voltage at a side of a power supply, a stable-state magnetic flux calculation unit which calculates three line-to-line stable-state magnetic fluxes, based on the voltage at the side of the power supply, a phase determination unit which determines a phase in which phases of the three line-to-line stable-state magnetic fluxes are respectively the same in polarity as phases of the three line-to-line residual magnetic fluxes, and a closing unit which closes the circuit breaker in the phase determined by the phase determination unit.

Respective contact terminals in respective arc-suppressing spaces of respective breakers are opened at a voltage zero point of any phase of three phases, simultaneously among the three phases. If current breaking is carried out for the three phases at the same time, when the breakers of the three phases are opened, the residual magnetic levels of the respective phases of a transformer can be controlled so that the residual magnetic flux level of the phase opened at the voltage zero point is maximum (for example, −2 K or +2 K) and the residual magnetic flux level of the other two phases are opposite in polarity to the residual magnetic flux level of the phase concerned and equal to substantially the same residual magnetic flux (for example, +K and +K or −K and −K) which is equal to about one half of the residual magnetic flux level of the phase concerned. Accordingly, by throwing the phase broken at the voltage zero point at a first time, the difference in residual magnetic flux between the second throwing phase and the third throwing phase just after the first phase is thrown can be substantially nullified.

The invention provides a circuit board cleaning agent replacing trichloroethylene. The circuit board cleaning agent replacing the trichloroethylene comprises the following components in mass percentage: 15-60% of cycloalkane, 10-20% of ether additive, 10-20% of ketone additive, 5-15% of ester additive and 15-30% of polyfunctional group additive. The circuit board cleaning agent is excellent in cleaning ability for residual fluxing agent and rosin on a circuit board in electronic industry, high in cleaning speed, rapid in evaporation, free of residue, low in toxicity, environment-friendly and efficient.

The invention discloses a hexagonal crystal M+W mixed type sintered permanent magnetic ferrite magnet and a preparation method thereof. The composition formula of the hexagonal crystal M+W mixed type sintered permanent magnetic ferrite magnet is represented by Cax1Srx2Bax3LaxFe2+aFe3+bOy, wherein x1 is 0.1-0.3, x2 is 0.2-0.5, x3 is 0.1-0.4, x is 0.1-0.3, a is 0.1-1.0, b is 12.0-14.0, 12.1<=a+b<=15.0, and y=1+1/2x+a+3/2b. Lanthanum oxide is added, the mole number of iron in the M type ferrite is enhanced, and the oxygen concentration in the sintering process is controlled to provide a appropriate non-oxidizing atmosphere so as to inhibit the generation of the alpha-Fe2O3 phase, so that the M+W mixed type magnetoplumbite structure can be generated in the original M type permanent magnetic ferrite. The invention has the following advantages: (1) compared with the single-phase M type ferrite, the invention enhances the residual flux density (Br) of the material, and maintains the high coercive force (Hcj); (2) compared with the single-phase W type ferrite, the invention has simpler production technique, and can perform industrial production only by slightly adjusting the M type permanent magnetic ferrite production technique; and (3) the magnet is free of rare and noble metal cobalt, and thus, the cost is lower.

The invention discloses an excitation permanent magnet which is used on a rotor of a rotating electric machine, wherein more than two kinds of permanent magnets with different characteristics are combined, the excitation permanent magnet is divided into more than three parts along the width direction, a high coercive force permanent magnet A is used within a range which takes the central axis (i.e. d axis) of the excitation permanent magnet as a center, as for the part which is deviated outward from the d axis, a permanent magnet B group which has low coercive force and high residual flux density compared with the permanent magnet A is used. The mixed magnet of two magnets which have different using characteristics is taken as the excitation permanent magnet, the input amount of the high-priced and coercive force magnets is reduced, so the cost is reduced, and resources are protected.

Provided is a magnetizing inrush current suppression device that is capable of accurately computing residual fluxes of a three-phase transformer and suppressing a magnetizing inrush current. The magnetizing inrush current suppression device (10) is equipped with: a voltage measurement unit (1) for measuring respective phase voltages of the transformer (23) and system voltages of the respective phases; an effective opening timing computation unit (2) for computing effective opening timing at which instantaneous values of the phase voltages of the three phases all converge to a value of zero; a core flux computation unit (3) for computing fluxes of the respective phases of the core of the transformer (23) by means of integration of the respective phase voltages; an effective residual flux computation unit (4) that takes, among the fluxes of the respective phases, the fluxes of the respective phases obtained at the effective opening point as effective residual fluxes in order to compute effective residual fluxes of the respective phases; a closing phase angle computation unit (5) for computing a closing phase angle for a system-side breaker (21) on the basis of the effective residual fluxes of the respective phases; and a closing phase angle control unit (6) for closing the system-side breaker (21) on the basis of the system voltages of the respective phases and the closing phase angle.

The invention discloses a method for removing flux from the surface of a substrate and a chip on the substrate. The method comprises the following steps of 1, cleaning flux on the substrate and the chip on the substrate by a water-based cleaning reagent firstly; 2, performing cleaning on the substrate and the chip on the substrate after being cleaned in the step 1 by adopting a bromopropane gaseous phase cleaning technology; and 3, performing argon plasma cleaning on the substrate and the chip on the substrate after being cleaned in the step 2 by adopting a plasma cleaning system. By adoptionof the method, the flux and pollutants on an electronic assembly can be removed, and the residual flux in the tiny gaps also can be completely taken away; in addition, the surface activity on the electronic assembly also can be changed, and the surface bonding state between a transmission line and a gold wire bonding pad also can be improved, thereby improving the bonding adhesive property and improving the bonding process reliability; by virtue of the method, the cleaning efficiency is improved, the yield is high and the process is simple; and low toxicity can be realized as far as possible on the basis that the cleaning capability can be satisfied, and strong respiratory tract irritation can be avoided.

A method for reducing the inrush current of an inductive load, particularly a transformer, comprising the following steps: a) connecting a DC power source to the transformer for a time tc, to magnetize its magnetic core until saturation is reached, and connecting the transformer to the AC mains via an electromechanical switch, in an initially open position; b) disconnecting the transformer from the DC power source, the magnetic flux being reduced to its residual value; c) closing the electromechanical switch to complete the connection, this connection point being determined by the phase angle selected from the sinusoidal signal of the voltage power lines, in such a way that magnetic flux corresponding to the steady state voltage equals the residual magnetic flux that remains when the transformer is disconnected from the DC power source.

The invention provides a duality-principle-equivalent-model-based residual flux measuring method for iron cores and yokes of a three-phase three-core-limb transformer. The measuring method comprises the steps: considering eddy-current loss resistance and inductance and zero sequence magnetic flux eddy current equivalent resistance and inductance for iron cores and yokes of a three-phase three-core-limb transformer; establishing a transient analysis model based on a duality principle for the three-phase three-core-limb transformer; applying width-controllable pulse voltage to any two phases at a winding of the low voltage side of the transformer; utilizing a multichannel oscilloscope to acquire voltage signals at different positions of the transformer; and performing integration operation processing to obtain residual flux values of the three core limbs and the upper and lower yokes. The duality-principle-equivalent-model-based residual flux measuring method for iron cores and yokes of a three-phase three-core-limb transformer can accurately measure the most original residual flux in the iron cores and yokes of the three-phase three-core-limb transformer, and has the advantages of being light in test equipment, being safe in the test process and being high in efficiency. After the residual flux test for the first time, the residual flux changes so that measurement through the measuring method again has no reproducibility.

There is provided a coercivity performance determination device for a coercivity distribution magnet that is capable of determining, in a short period of time, with precision, and at as low a testing cost as possible, whether or not each part of one coercivity distribution magnet has a coercivity that is equal to or greater than the required coercivity. A coercivity determining device of the present invention comprises: a substantially C-shaped magnetic body; excitation means that generates a magnetic flow in the magnetic body; and a flux meter that measures the residual magnetic flux of the coercivity distribution magnet. Protrusions are provided at corresponding positions on two opposing end faces of the magnetic body, and the coercivity distribution magnet is held between the two protrusions to form an annular magnetic circuit. An external magnetic field generation means is formed by magnetic regions caused by the protrusions and non-magnetic regions comprising the air in the periphery thereof. An external magnetic field that is generated when magnetism flows through the protrusions is adjusted in such a manner that a reverse magnetic field, which comprises the sum of the external magnetic field and the demagnetizing field of the coercivity distribution magnet, corresponds to the coercivity required of each part of the coercivity distribution magnet. The residual magnetic flux when this has acted as the reverse magnetic field is measured with the flux meter to determine coercivity performance.

A motor includes a magnet and a coil. α2=[{(Br2−Br1)/Br1}/(T2−T1)]×100≧−0.10 and α3=[{(Br3−Br1)/Br1}/(T3−T1)]×100≦−0.12 are satisfied. In the magnet, Br1 (mT) is a residual magnetic flux density at T1 (° C.), Br2 (mT) is a residual magnetic flux density at T2 (° C.), and Br3 (mT) is a residual magnetic flux density at T3 (° C.), and α2 (%/° C.) is a temperature coefficient at a target temperature of T2 (° C.) with respect to a reference temperature of T1 (° C.), and α3 (%/° C.) is a temperature coefficient at a target temperature of T3 (° C.) with respect to a reference temperature of T1 (° C.) in conditions of T1=23, T2=60, and T3=180.

An optical device includes a Faraday rotator made of a bismuth substituted rare earth iron garnet single crystal (BIG) having a Faraday rotation of 45 degrees, and permanent magnets arranged beside the Faraday rotator to define two or more areas of a single domain structure in the Faraday rotator. Adjacent areas are magnetized in opposite directions to cause the polarization planes of light beams passing through the adjacent areas to rotate in opposite directions. The optical device satisfies the relation expressed by Hs/Br/DH>DeltaD/2>0 where Hs (Oe) is a saturation magnetic field of the BIG, DH (cm<-1>) is a rate of change in magnetic field in the proximity to a boundary between the adjacent areas, Br (Gauss) is a residual flux density of the permanent magnets, and DeltaD is a distance between the two light beams.