141results about How to "Small excitation current" patented technology

The invention discloses a bidirectional magnetic saturated time difference fluxgate sensor, which is characterized in that two ends of a sensor magnetic core are wound with exciting coils, the middle section of the sensor magnetic core is wound with induction coils, output poles of the induction coils are connected with an amplifying circuit, and the amplifying circuit is connected with a counting display circuit through a band-pass filter circuit and a retardation shaping circuit. By detecting and calculating a positive negative pulse time difference value output by the fluxgate sensor in a time domain, the strength of the measured magnetic field is judged. Compared with the prior fluxgate sensor, the detection circuit is simple, the measurement stability of the system is ensured without a feedback structure, a complex subsequent circuit is not needed, the required excitation current is lower, the data processing is simple, the measured relative quantity is little, the integral volume and power consumption of the sensor are effectively reduced, and the measurement result is acquired quickly. The fluxgate sensor avoids a filter-phase-sensitive demodulation-smooth filter circuit of the prior fluxgate sensor, makes up the defect that the prior fluxgate sensor has harsh process requirement, and achieves the digitized magnetic measurement of the fluxgate sensor.

The invention relates to a parallel-magnetic-circuit hybrid-excitation permanent magnet motor, which comprises a case. A stator consisting of a stator core and a stator winding, and a rotor consisting of a permanent magnet, a rotating shaft, a rotor core and an excitation winding are installed in the case. The stator winding is distributed in a slot which is circumferentially arranged in the stator core. The permanent magnet and the excitation winding are arranged on the rotor core. Magnetomotive forces established by the permanent magnet and the excitation winding are connected in parallel in the form of magnetic circuits. By adjusting the current of the excitation winding, the air-gap magnetic field of a ferromagnetic pole can be conveniently adjusted to realize the adjustment of the air-gap magnetic field of the motor. Since a permanent magnet magnetomotive force and an electrically excited magnetic magnetomotive force are connected in parallel in the form of magnetic circuits, the needed exciting current is smaller and the efficiency of the permanent magnet motor is kept to be high; since magnetic fluxes produced by two kinds of excitation magnetomotive forces flow through the same motor iron core, the material utilization rate is high and the power density of the permanent magnet motor is kept to be high; and the structure of the parallel-magnetic-circuit hybrid-excitation permanent magnet motor is similar to the structure of a common permanent magnet synchronous motor, an axial magnetic circuit and an additional air gap do not exist and the motor has the advantage of simple structure.

The invention discloses a mono-stability self-locking gas clearance permanent operating mechanism used for large open contact and high voltage breaker in the medium and high voltage electrical switch field. When used for medium voltage breakers, the mechanism can lower exciting current and increase electromagnetic force. The permanent magnetic operation mechanism mainly consists of a magnetic circuit system, a transmission system, a locking system, and a supporting system. Permanent magnet of the magnetic circuit system is embedded between the internal and external static iron cores; magnetic coils are embedded in the coil groove constituted by the internal and external static iron cores and dynamic iron cores. Clearance is reserved between the internal, external static iron cores and dynamic iron core. Core shaft is pressed on a limiting block by a nut after pulling through a lock disc, a dynamic iron core, and a switch spring, an end cover, and a limiting block in the magnetic circuit system. The invention can well control the closing and opening speed of switch contacts and reduce the collision and bouncing of contacts. Suitable for breakers of different voltage grades, particularly high voltage vacuum breakers with big open contacts, the invention can lower exciting current and energy consumption more reliably.

The invention discloses an electromagnetic induction heating press-roller, which has an integral double-end supporting structure and comprises a rotating device and a fixing device, wherein the rotating device consists of an action roller and a rotating shaft which are connected; the rotating shaft inputs a rotating torque to drive the action roller to rotate; the fixing device consists of a fixed shaft, a sleeve arranged on the outer side of the fixed shaft, magnetizers and excitation coils; through the magnetizers and excitation coils segmentedly installed outside the sleeve, a magnetic airgap is formed between the outside end face of the fixed magnetizer and the inner circular face of the rotating action roller; the alternating magnetic field forms a circuit through the magnetizer, the air gap and the action roller metal; the magnetic field in the action roller forms an eddy current so as to uniformly heat the working face of the rotating action roller. Since a structure of axially segmented magnetizers and excitation coils is adopted, a magnetic circuit is formed on the working face metal of the heating roller only to avoid the magnetic circuit penetration of the non-heating working part and reduce the excitation current, and simultaneously prevent the machine parts from overheating; besides, the induction heating efficiency can be improved so as to control the axial temperature gratitude of the heating roller continently.

The invention is concerned with retarder for vehicle, relating to stator and rotor eddying around the stator making of soft magnetic material. There is work clearance between the stator and rotor and there is excitation loop embeds on the stator. The work clearance is filled with powder medium of soft magnetic or liquid medium containing soft magnetic power. There is a main magnetism route made of the rotor and the clearance round the excitation loop, and when the excitation loop is electrifying, the powder medium of soft magnetic or liquid medium containing soft magnetic power of the work clearance will produce trig torque. When the vehicle moves slowly or is rest, this retarder for vehicle can give out large trig torque. The excitation current, volume and weight are small.

The invention relates to a mixed switch reluctance motor, belonging to the electric motor field. The invention overcomes the defects that the installation of a winding is difficult, the manufacturing process is comparatively difficult, the space factor is low, and the like due to the structure of the existing switch reluctance motor. In the invention, the mixed switch reluctance motor consists of a stator and a rotor, wherein, the stator is composed of a permanent magnet, an exciting winding and a stator core; an air gap is arranged between the excircle of the rotor core of the rotor and the inner circle of the stator core, the exciting winding is embedded in an tooth socket of the stator core, while the permanent magnet is embedded into the tooth part of the stator core along the axis direction. In the invention, a high-performance tangential magnetizing permanent magnet is used, and the permanent magnet is embedded into the tooth part of the stator core along the axis direction, thus forming a mixed excitation switch reluctance motor; compared with the existing mixed excitation switch reluctance motor, the motor in the invention has unchanged number of permanent magnets and increased usable area of the stator groove winding, thus improving the performance and volume ratio and the performance and weight ratio of the motor of the invention, reducing cost and simplifying manufacturing process. The motor of the invention can be used as an electric motor and an electric generator.

The invention discloses a three-stage brushless synchronous start generator structure and a start control method thereof. The three-stage brushless synchronous start generator structure comprises an auxiliary permanent magnet exciter, a main exciter, a main motor, a rotary rectifier and a three-phase full-bridge inverter; the main exciter, the main motor and the rotary rectifier are sequentially connected; and the three-phase full-bridge inverter is connected with the main motor. The structural complexity of the three-stage brushless synchronous start generator can be reduced; the working reliability can be improved; the start control method can be simplified; the rotation speed range of the main motor can be expanded; the design capacity of the main motor can be reduced; and start of the generator can be completed effectively and stably.

The invention discloses a wide input range dual-bridge LLC resonant converter, and belongs to the technical field of electric power electronic transformation. The inverter comprises an input direct current voltage source Vin, bus dividing capacitors Cin1 and Cin2, switch tubes Q1, Q2, Q3, Q4, Q5 and Q6, a resonant capacitor Cr, a resonant inductor Lr, a magnetic inductor Lm, a transformer T, rectifier diodes D1 and D2, an output filter capacitor Co and a load Ro. By controlling the ratio between the time that the converter works in full-bridge and the tome that the converter works in half-bridge working in one period, an input voltage waveform of a resonant groove is changed, and thus adjusting the output of the inverter is realized. The inverter adopts constant-frequency PWM control, switching frequency is equal to resonant frequency, primary side current is decreased, and conduction loss is reduced. The inverter can realize primary side main switch tube ZVS opening and secondary side rectifier diode ZVS turn-off in a full-input-voltage scope and a full-load-change scope, reduces switching loss, and increases watt intensity. The wide input range dual-bridge LLC resonant converter has the advantages of wide input voltage range, constant-frequency control, benefit for magnetic device design and optimization, and the like.

The invention discloses a self-boosting doubly-salient brushless direct-current power generation system. An armature winding and two excitation windings which are in magnetic coupling mutually are arranged in a doubly-salient motor of the self-boosting doubly-salient brushless direct-current power generation system. The armature winding, a bridge rectifier circuit, the first excitation winding, a diode, a first power switch tube and a capacitor are respectively and sequentially connected, the second excitation winding is sequentially connected with an asymmetrical half-bridge circuit and a direct-current excitation source, an engine detecting and controlling unit is used for detecting the output voltage, the output current and the excitation current of the power generation system and controlling the duty ratio of the asymmetrical half-bridge circuit and the first power switch tube. The invention further discloses a control method of the self-boosting doubly-salient brushless direct-current power generation system. According to the method, under the conditions of the constant rotation speed and the variable rotation speed, the efficiency and the output power of the power generation system are improved through coordination control of the duty ratio between the excitation current and the first power switch tube.

The invention relates to a mechatronic alternating current (ac) motor stator core of a compressor and a wire embedding method thereof and especially relates to an ac motor stator core of a piston refrigeration compressor used in a refrigerator. The motor stator core comprises an iron core body. A rotor aperture is arranged in a middle part of the iron core body. Wire embedding slots, which penetrate along an axial direction, are arranged along a circumferential direction of a hole wall of the rotor aperture. Inner sides of the wire embedding slots are provided with notches. A circumferential width (chord length) Bs0 of the notch is 0.1-1.0 mm. By using the stator core and the method of the invention, iron core surface losses and tooth pulse vibration losses can be reduced; an air gap coefficient is decreased; a field current is reduced; a power factor is raised so that working efficiency of the motor can be raised. Through redesigning a slot type size of the wire embedding slot, the additional losses generated by a harmonic field can be reduced so that the working efficiency of the motor can be further raised. A computer simulation experiment shows that the working efficiency of the motor can be increased by 1.5% by using the stator core of the invention. The stator core and the method is especially suitable for the single-phase asynchronous ac motor used in the totally enclosed refrigeration compressor.

The invention provides an axial magnetic bearing, and particularly relates to the axial magnetic bearing of which the radial torsion can be controlled. The axial magnetic bearing comprises a stator part and a rotor, wherein the stator part comprises an inner-ring stator core, an outer-ring stator core, a permanent magnet and coils; the inner-ring stator core adopts an integral ring structure; the outer-ring stator core comprises two stator core magnetic poles which are arranged in the +X direction and the -X direction (or the +Y direction and the -Y direction); the coils are wound on the stator core magnetic poles respectively; an axial magnetic airgap is formed between the stator part and the rotor; the radial inner side of the permanent magnet is connected with the inner-ring stator core; and the radial outer side of the permanent magnet is connected with the outer-ring stator core. The axial magnetic bearings provided by the invention are required to be used in pairs, so that the radial torsion of the rotors can be controlled when the outer-ring magnetic poles of two axial magnetic bearings are placed in different positions, which greatly reduces the axial size of the system. The axial magnetic bearing further has the advantages of low rotation loss, reliable performance, convenience in control, and the like.

A signal lighting circuit of a railway train operation sand table LED model comprises a lamp filament relay and n signal lamp circuits. A coil of the lamp filament relay is respectively connected with the signal lamp circuits in series to be conducted with a power source by finishing the conversion of the signal lighting function and the interlocking logic function in the circuits, the resistance of the coil of the lamp filament relay ranges from 340 omega to 600 omega, and the exciting current of the coil of the lamp filament relay ranges from 20mA to 40mA. The structures of the n signal lamp circuits are the same, and each signal lamp circuit comprises a bulb loop and a bridge rectifier circuit. Each bulb loop comprises a capacitor, a resistor and a light emitting diode, wherein the resistor is connected with the light emitting diode in series and then is connected to the two ends of the capacitor in parallel, one input end of the bridge rectifier circuit is connected with a movable contact of the lamp filament relay, the other input end of the bridge rectifier circuit is connected with the power source, and a direct current output end of the bridge rectifier circuit is connected with the two ends of the capacitor. The signal lighting circuit of the railway train operation sand table LED model is low in energy consumption and failure rate, high in circuit reliability and capable of reducing maintenance workloads and space occupied by the circuits.

Provided are a current detecting circuit and a transformer current measuring system, wherein transformer currents (primary current and secondary current) can be measured without deteriorating operations of an element and a circuit even when a transformer having a large excitation inductance is used in the cases where the element and the circuit which do not normally operate without using a transformer having a small excitation inductance are connected to the primary side. A current detector (CT) (current transformer) is connected in series to the primary winding (111) of a transformer (11), and an inductor (La) is connected in parallel to the serial connection of the primary winding (111) and the current detector (CT). Based on the value of a primary current (IT) detected by means of the current detector (CT), the secondary current (I2) of the transformer (11) is measured.

The invention discloses a resin insulation dry type transformer with a three-dimensional roll iron core. The resin insulation dry type transformer comprises a transformer base, an upper clamping part, a lower clamping part and a three-dimensional roll iron core, wherein the upper clamping part and the lower clamping part are correspondingly arranged on the transformer base up and down, and the three-dimensional roll iron core is clamped between the upper clamping part and the lower clamping part; the three-dimensional roll iron core comprises three single frames, the middle parts of the single frames are hollowed out, and the single frames are of rounded rectangle structures in shape; the three single frames are arranged and spliced together in an equilateral triangle shape three-dimensionally; each single frame is formed by continuously winding a plurality of silicon steel trapezoid material straps in sequence; a coil is wound at the joint of every two single frames respectively; each coil is integrally poured by a curing agent and is formed through heating curing; and the exterior of each coil is encapsulated by epoxy resin respectively. The resin insulation dry type transformer is provided with the three-dimensional roll iron core, and has the characteristics of energy conservation and material saving, low no-load loss, low no-load current, low noise, good electrical performance, low partial discharge value, high lightning impulse resistance, high short-circuit resistance and high mechanical strength.

An embodiment of the invention discloses a control method of a convertor, an apparatus and a system. The method comprises the following steps of acquiring a modulating wave; according to the modulating wave, calculating a first injection amount; carrying out size control on the first injection amount and outputting a second injection amount, wherein an absolute value of a difference value of the second injection amount and a third injection amount is less than or equal to a preset threshold; the third injection amount is the injection amount calculated at the last time; superposing the second injection amount into the modulating wave so as to obtain the controlled modulating wave; using the controlled modulating wave to carry out discontinuous pulse width modulation on the convertor. In the embodiment of the invention, the size of the injection amount is controlled so that a speed of the injection amount which is superposed to an original modulating wave is slowing down; an exciting current can be effectively reduced so that a peak value of the exciting current can be effectively reduced too; and noises are decreased.

The invention provides a rotor alternate-angle stator magnetic isolation type axial permanent magnet auxiliary double-salient-pole motor and belongs to the field of double-salient-pole reluctance motors. The double-salient-pole motor comprises two groups of magnetic isolation type stators, two groups of circumferentially alternate-angle rotors, a rotating shaft, a casing, an axial ring sleeve type composite permanent magnet, a magnetic conduction strip and exciting windings. The axial ring sleeve type composite permanent magnet is annularly sleeved at the center of the rotating shaft. The two groups of circumferentially alternate-angle rotors are fixed on the rotating shaft on both sides of the axial ring sleeve type composite permanent magnet. Each magnetic isolation type stator comprises a partitioned stator yoke and a salient pole and each salient pole is wound with one exciting winding. The magnetic isolation type stators and the circumferentially alternate-angle rotors are correspondingly arranged and an air gap is arranged. The casing and the rotating shaft are coaxial. The inner wall of the casing is provided with six magnetic isolation strips. The magnetic isolation type stators are fixed in the magnetic isolation grooves of the casing. The magnetic conduction strip is used for connecting stators on the two sides to be served as a magnetic bridge. According to the invention, the output torque is effectively improved and the armature current is reduced in certain conditions. The torque ripple of the motor is improved and the loss of the yoke part of each stator is lowered. Therefore, the operating efficiency of the motor is improved and the performance indexes of the motor are better.

The invention discloses a method for controlling a double-stage matrix converter-synchronous generator system. Closed-loop control is conducted on a unidirectional switch level voltage modulation ratio so as to automatically adjust the field current of a generator, when load power is small, the counter electromotive force amplitude of the generator is reduced to ensure that the system can normally work, the range of the load power is widened, and meanwhile a converter works in a good state, and the operating performance of the system is improved. According to the method for controlling the double-stage matrix converter-synchronous generator system, the control idea is simple, a hardware circuit does not need adding, and the method is of a great innovative significance and has high practical value.

The invention discloses an axial electrical excitation composite rotor circumferential misplacement reluctance motor control system and method, and belongs to the technical field of electrical appliance automatic control. The axial electrical excitation composite rotor circumferential misplacement reluctance motor control system comprises a DSP (Digital Signal Processor), a position sensor, a speed sensor, a current sensor, a level reversion chip, a three-phase asymmetrical half-bridge power converter, a driving circuit and the like. A controlled motor comprises a motor revolving shaft, a magnetic conductive material, a central electric excitation coil, a stator salient pole, a rotor salient pole and the like. The method comprises the following steps: generating a new PWM (Pulse-Width Modulation) duty ratio according to data transmitted by the position sensor, the speed sensor and the current sensor through the DSP; and adjusting current of a three-phase winding or adjusting current of the electric excitation coil. The electric excitation coil is arranged between two groups of stators, and a rotor circumferential misplacement structure is adopted for running, so that crest connection of torque between two sets of stators and rotors is realized effectively. Double-closed-loop PI (Proportional-Integral) control is adopted, so that the dynamic response speed and interference resistance of the control system are improved greatly, and efficient continuous speed adjustment control of a motor can be realized easily.

The invention discloses a direct torque control system without a flux linkage loop. The direct torque control system comprises a motor and a control system. The control system comprises a coordinate transformation module for detecting three-phase currents ia, ib and ic and three-phase voltages ua, ub and uc at an output end of a three-phase inverter module and converting the currents and voltagesinto i[alpha] and i[beta], and u[alpha] and u[beta]; a torque and rotor position estimation module for estimating stator flux linkages [psi][alpha] and [psi][beta] and a rotor position [theta]r in accordance with i[alpha], i[beta], u[alpha], and u[beta], and calculating an observed torque value Te; a PI speed regulator for calculating a given torque value (shown in the description) according to the rotational speed of the permanent magnet synchronous machine; a reference vector generation module for generating reference voltages usd and usq according to the difference between the observed torque value Te and the constant torque value (shown in the description) and a torque angle [delta]; an SVM control module for synthesizing reference voltages usd and usq into optimal voltage vectors Sa,Sb and Sc; and a three-phase inverter module for outputting a three-phase alternating current according to the input optimal voltage vectors Sa, Sb and Sc to realize the control over the rotational speed of the permanent magnet synchronous machine.

The invention discloses an amorphous alloy plane stepped iron core, which comprises a template, small iron cores, a big iron core and an internal template mould. The template is divided into an external template and an internal template. The big iron core is located on the inner side of the external template, two small iron cores are arranged in parallel in the big iron core, the internal template is disposed in the middle of each small iron core, the internal template mould is installed in the internal template, and the external template enables the entire core to be bound and formed through binding steel belts. On the design conditions of equal iron core magnetic density, turns per coil and specifications for using wires, materials of circular coils winding round the amorphous alloy plane stepped iron core only account for 91% of square coils winding amorphous alloy single-belt-material iron cores, and materials are effectively saved. In addition, the amorphous alloy plane stepped iron core adopts a closed structure, lap joint ports are not provided, generated magnetizing current is small, generated noise is small, and the amorphous alloy plane stepped iron core is beneficial for creating good work and life environment.

The invention relates to a motor stator component structure with a magnetic slot wedge, which is characterized by comprising an upper stator coil and a lower stator coil which are arranged in a stator punching; the magnetic slot wedge is arranged below the lower stator coil, a top cushion is arranged between the top end surface of the upper stator coil and the bottom roof of the stator punching, a middle cushion is arranged between the top end surface of the lower stator coil and the bottom end surface of the upper stator coil, an adjustment cushion and an expansion cushion are arranged between the bottom end surface of the lower stator coil and the bottom frame of the stator punching, the adjustment cushion is arranged below the expansion cushion, and the top end surface of he magnetic slot wedge is in contact with the bottom end surface of the adjustment cushion. The magnetic slot wedge of the invention can effectively improve the magnetic potential wave shapes of air gaps, reduce exciting currents, increase the power factors and efficiency of a motor, and reduce the temperature rise, noise and vibration of the motor. The magnetic slot wedge can ensure that the motor can be reliably fixed in the stator slot shape during the operation process without phenomena of loosing, cracking, tissue loosing, surface bubbling and the like, thus avoiding the friction between the stator and the rotator of the motor caused by the cracking, loosing, dropping and the like of the magnetic slot wedge.

The invention relates to a mixing adjustable excited non salient pole rotor for a large air-cooled turbine generator, which belongs to the technical field of motors and solves the problem of high temperature in the rotor of a traditional turbine generator caused by enhancement of current density of rotor windings in order to increase capacity. The rotor comprises a four-pole rotor iron core and two sets of rotor windings; four large teeth and four groups of small teeth of the four-pole rotor iron core are distributed at intervals; tooth grooves are arranged between adjacent teeth; the bottom center of each tooth groove is provided with a rotor assistant groove; the width of the rotor assistant groove is smaller than that of the tooth grooves; the rotor also comprises a plurality of permanent magnets; the bottom of each tooth groove is embedded with a permanent magnet; each two groups of small teeth is wound with a set of rotor winding; and the rotor windings are positioned above the permanent magnets. The rotor is used for improving the traditional turbine generator.

The invention discloses a superconducting electric electromagnetic hybrid maglev train, which comprises L-shaped suspension frames and an I-shaped ground rail, and is characterized in that the upper end of each suspension frame is connected with a train body through an air spring; the suspension frames are arranged on the two sides of the ground rail, and the suspension frames and the ground railare arranged at intervals. A plurality of superconducting magnets is arranged at the lower end of each suspension frame. An 8-shaped upper-layer suspension coil and an 8-shaped lower-layer suspensioncoil are arranged at the upper end and the lower end of the ground rail respectively, an upper-layer power generation coil and a lower-layer power generation coil are arranged at the lower end of thesuspension frame, and the upper-layer suspension coil is electrically connected with the lower-layer suspension coil; and a propelling coil is arranged above the upper-layer suspension coil. The invention has the advantages of large operation air gap, self-stabilization, good suspension guiding dynamic performance, better curve passing capacity, higher superconducting magnet magnetic field utilization rate and lower track construction cost.

The invention relates to magnet control type parallel reactor controllable afterflow method and excitation system. The present method comprises following steps: a controllable afterflow branch constituted by thyristor valve parallel to DC bus two pole is installed at magnet control type parallel reactor excitation system, the cathode of thyristor valve is connected with anode of DC bus, the anode of thyristor valve is connected with cathode of DC bus;when rectifier is under normal operation state, DC excitation current, rectifier and excitation branch constitutes loop, thyristor valve of controllable afterflow branch does not conduct; when open phase operation or three phase tripping of transmission line occurs, control circuit locks rectifier and triggers pulse and controllable afterflow branch thyristor valve, controllable afterflow branch conducts and DC exitation current transfers from rectifier to controllable afterflow branch to constitute loop, thyristor valves of rectifier totally shut off. The invention solves the technical problem of magnet control type parallel reactor excitation branch afterflow, which is significant to safety and reliable operation of magnet control type parallel reactor.

The invention discloses a spinel composite ferrite material, and a preparation method thereof, and belongs to the technical field of ferrite material preparation. The spinel composite ferrite material is prepared from a Li series main material and a Ni series main material at a mass ratio of 1:99-99:1, and an additive; the Li series main material is prepared from 67.0 to 74.0mol% Fe2O3, 16.0 to 24.0mol% of ZnO, and 2.0 to 17.0mol% of Li2CO3; the Ni series main material is prepared from 47.0 to 48.5mol% of Fe2O3, 18.0 to 19.5mol% of ZnO, 25.0 to 26.5mol% of NiO, and 5.5 to 10.0mol% of CuO; the additive comprises, by the weight amount of oxides, 0.10 to 1.00wt% of Bi2O3, 0.01 to 0.10wt% of V2O5, 0.60 to 0.70wt% of BST, 0.001 to 0.05wt% of CaO. The spinel composite ferrite material is low in loss, high in the Curie temperature, and low in coercive force.

The invention provides a low-power-consumption electromagnetic flow converter mainly comprising an exciter circuit, a power source, a sensor, a signal conditioning circuit and a single-chip microcomputer interface circuit. The low-power-consumption electromagnetic flow converter is characterized in that the exciting mode of the exciter circuit is pulse rectangular wave exciting; the power source has two combination modes of lithium thionyl chloride batteries; the signal conditioning circuit comprises an instrument amplifier, a low pass filtering circuit, a resistance-capacitance coupling circuit and a high gain amplifying circuit; the single-chip microcomputer interface circuit comprises a single-chip microcomputer, a reset circuit, a crystal oscillator, an A / D input unit, a display output unit, a 485 communication output unit, a storer circuit, and a JTAG debugging interface. The low-power-consumption electromagnetic flow converter is characterized by low power consumption, small size and field display and guarantees measuring accuracy.

The present invention provides a switching power supply with high conversion efficiency and facilitates reducing the size thereof. The switching power supply includes a half-bridge circuit including a first series circuit formed of switching devices Q1 and Q2 and connected between the output terminals of a DC power supply; and a second series circuit connecting primary inductance Lr1 of transformer T1, primary inductance Lr2 of transformer T2 and capacitor Cr in series. The second series circuit is connected between the output terminals of the half-bridge circuit, and is made to conduct a series resonance operation. The switching devices Q1 and Q2 is controlled at the ON-duties of 0.5 for reducing the breakdown voltages of rectifying diodes D1 and D2 on the secondary side of transformers T1 and T2 and for improving the conversion efficiency of the switching device.

The invention provides an open type transformer three-dimensional roll-core. The three-dimensional roll-core is characterized in that the roll-core is composed of three identical iron core frames made of silicon steel sheets, and each iron core frame is formed by a hexagonal frame defined by an upper half frame and a lower half frame; the upper half frame is provided with a left and a right upper half frame bevel edge; the lower half frame is provided with a left and a right lower half frame bevel edge; the silicon steel sheets of two bevel edges at the same sides of the upper half frame and the lower half frame are arranged in a staggered manner; the silicon steel sheets of two bevel edges at the same sides are mutually inserted together to form the bevel edges of the iron core frames; the silicon steel sheets of each layer are connected at bending positions of the silicon steel sheets. The open type transformer three-dimensional roll-core has the positive effects that an iron core joint position of the roll-core is completely out of a coil, joint position fastening treatment can be very conveniently carried out after the iron core joint position is sheathed in the coil, and the roll-core is very conducive to transformer noise reduction and loss reduction. If a fault happens, the upper half frame of the iron core frame can be conveniently dismantled and the coil can be pulled out for maintenance.