61results about How to "Suppression of harmonic components" patented technology

The invention discloses a grid-connected control method and system based on a virtual synchronous generator. The method comprises the steps as follows: simulating synchronous impedance with a synchronous impedance method based on cascade connection of an order-reduced resonator and a three-order generalized integrator to improve stability of the system, inhibit current deviation formed by load disturbance and realize power equalization, and inhibiting imbalance of output voltage and harmonic component by using quasi-proportional resonance controller. An order-reduced resonator phase-locked loop is combined with a quasi-synchronous parallel algorithm, asymmetry of grid voltage and output voltage of an inverter as well as the effect of harmonic waves on detection accuracy is avoided, the frequency, amplitude and phase of the output voltage of the virtual synchronous inverter track grid voltage quickly without static errors by the aid of the quasi-synchronous parallel algorithm, so that flexible off-grid / grid-connected switching is realized, the power supply reliability of the system is improved, and the electric energy quality is improved.

The invention relates to a permanent-magnet synchronous motor torque ripple suppression method based on coordinate transformation harmonic compensation. Three-phase current is acquired and converted into stator current in a two-phase static coordinate system; the stator current in the two-phase static coordinate system is transformed to fifth, seventh, eleventh and thirteenth harmonic rotating coordinate systems; direct-current component is extracted from fifth, seventh, eleventh and thirteenth harmonic current in the corresponding coordinate systems through a low-pass filter; a second-order low-pass digital filter based on speed adaptation is designed to extract harmonic of a specific order; and on the basis, a proportional integral current controller with cross coupling is designed to complete harmonic current suppression ultimately, thus suppressing torque ripple. Compared with the prior art, the harmonic content of output current can be reduced, and torque ripple, vibration noise and other negative effects of a permanent-magnet synchronous motor for electric vehicles can be reduced on the basis of permanent-magnet synchronous motor vector control.

The invention relates to a rotor of a high-quality and high-speed built-in permanent magnet motor and a magnetic steel structural parameter determining method thereof. In the invention, the whole section magnetic steel of each electrode of the rotor of a conventional built-in permanent magnet motor is divided into multiple sections of magnetic steel which have the same polarity and different widths; the multiple sections of the magnetic steel are respectively arranged in a rotor core; and reinforcing ribs with the function of magnetic isolation are arranged among the multiple sections of the magnetic steel. By reasonably modulating and determining the width and distribution of each section of the magnetic steel, the air gap magnetic density waveform approaches sine distribution; harmonic components are reduced to the greatest extent; the eddy current loss of the magnetic steel and the torque pulsation of the motor are simultaneously reduced; and the electromagnetic performance of the motor is enhanced. Furthermore, the multiple sections of the magnetic steel are arranged in the circumference along the rotor; the highest rotating speed of the safe operation of the rotor is greatly enhanced on machinery; the radial thickness which is needed by the magnetic circuit of the rotor is obviously reduced on the structure; the rotational inertia and weight of the rotor are reduced; the dynamic response of the motor is improved; and the requirements of a high-speed driving system on the performance of the motor are met.

The invention discloses a damping control method in a non-electrolytic capacitance permanent-magnet synchronous-motor air conditioning drive system and relates to a method for inhibiting resonance inthe built-in permanent-magnet synchronous-motor air conditioning drive system with an aim to solve the problem about resonance generated from interaction of an input side filter and a direct-current bus capacitor of the air conditioning drive system. The damping control method includes: 1), when the permanent-magnet synchronous motor runs, processing direct-current bus voltage by using a band-passfilter and multiplying the direct-current bus voltage by a coefficient K to obtain damping current; 2), performing processing according to the obtained damping current to obtain equivalent damping power and controlling the damping current by controlling the damping power, wherein the expression of the damping power is the damping current multiplied by the direct-current bus voltage; 3), changingoutput power of an inverter to achieve the damping power, generating an extra voltage reference value to have the output power of the inverter changed, and finally, generating an extra voltage commandsignal to have resonance in the system inhibited. The damping control method is applicable to the technical field of motor control.

The invention discloses an electric spring topological structure implemented based on a current source type inverter and a control method of the electric spring topological structure. According to the control method, a direct current control and harmonic suppression method is adopted; and when distortion occurs in the output current of a new energy power generation system, the current of a key load can be enabled to be pure sine by an electric spring (ES), a given value can be accurately traced, and the harmonic current is forced to flow into the ES through control. By the electric spring topological structure implemented based on the current source type inverter and the control method of the electric spring topological structure, the harmonic components of the voltage and the current of the key load can be effectively suppressed on the condition of high harmonic content in a power grid, and the sine degree of the key load is improved and the valid values of the voltage and the current of the key load are enabled to be constant.

The invention discloses a photovoltaic grid-connected control method and system based on a wave trap and a proportional resonance controller. The method comprises the steps of: establishing a maximumpower point tracking model, a positive and negative sequence separation model, a current control model and an inverter control model with harmonic suppression, wherein the maximum power point trackingmodel calculates the start or stop of maximum power point tracking according to an input voltage amplitude signal; enabling the positive-negative sequence separation model to calculate positive-negative sequence components of the power grid voltage; enabling the current control model to calculate a power grid active and reactive current reference value according to the power grid voltage amplitude;, wherein the inverter control model comprises a voltage outer loop control model with a wave trap and a current inner loop model adopting a proportional resonance controller added with harmonic suppression control, and calculates an inverter output voltage reference value according to the positive-negative sequence components of the power grid voltage and the power grid active and reactive current reference value. According to the invention, the interference of the harmonic component on the system under the asymmetric fault is solved, and the electric energy quality of the whole photovoltaic grid-connected system in the low-voltage ride through process is improved.

The invention relates to a propeller shaft frequency searching method based on improved noise envelope signal recognition. The method includes: enveloping an original hydrophone signal, and performingHilbert-Yellow transform on each wavelet packet signal to obtain a wavelet envelope signal; performing wavelet reconstruction to obtain an improved noise envelope signal; calculating a time correlation spectrum, take a line spectrum protruding at the peak of the low frequency band as the suspected shaft frequency; setting a step size smaller than the frequency resolution according to the demand;forming a suspected shaft frequency set with the suspected shaft frequency as the center; performing cyclic correlation calculation on a time correlation spectral signal on each suspected shaft frequency to obtain the frequency statistical amount of a cyclic modulation spectrum; and finally searching the shaft frequency of a target according to the frequency statistical amount. The method of the invention corrects axial frequency offset errors generated by the conventional cyclic modulation spectrum methods in the spectrum calculation process, improves the accuracy of the shaft frequency detection, greatly reduces the calculation amount of the loop iteration, and is convenient to implement in engineering application.

The invention discloses a method for obtaining a balanced and non-distortion total output current of a double-fed induction window power system with a series grid-side converter under the condition of an imbalanced harmonic-distortion grid voltage and relates to control over the series grid-side converter, a parallel grid-side converter and a motor-side converter. A voltage controller adopted by the series grid-side converter can achieve rapid restraint of the negative sequence of a stator, a fifth-harmonics voltage component and a seventh-harmonic voltage component, and therefore safe and stable operation of the motor is guaranteed. A reference current order of the parallel grid-side converter under a positive synchronous rotation coordinate axis system comprises the positive sequence and the negative sequence of a fundamental wave, the fifth-harmonics voltage component and the seventh-harmonic voltage component. A current controller adopted by the parallel grid-side converter can achieve accurate and rapid adjustment of a direct-current component, a frequency-doubling alternating-current component and a sixfold-frequency alternating-current component, so that it is guaranteed that the total output current of the system is balanced and free of distortion, and the quality of electric energy of a power grid which the double-fed induction window power system is connected to under the condition of the imbalanced harmonic-distortion grid voltage is effectively improved.

The invention discloses a clock signal generating method and system. The method includes the steps that initial clock signals are generated, the initial clock signals are analyzed to obtain the harmonic wave times, the harmonic wave amplitude value and the harmonic wave phase of a preset number of harmonic waves, then a preset number of harmonic wave signal generators correspondingly receive harmonic wave frequency control words and harmonic wave phase deviation control words sent by an upper computer, and all paths of initial harmonic wave clock signals are generated correspondingly; a preset number of harmonic wave amplitude controllers correspondingly receive harmonic wave amplitude value control words sent by the upper computer, adjust the amplitude of the initial harmonic wave clock signals, and correspondingly generates all the harmonic wave clock signals, so that all the paths of harmonic wave clock signals are made to be the same as the frequency and amplitude value of all the paths of harmonic waves of discrete clock signals, the phase difference is made to be 180 degrees, the purpose of eliminating the harmonic waves is achieved through amplitude value cancellation, the harmonic wave component of the fundamental wave frequency, caused by DAC nonlinear characteristics, in output singles is effectively inhibited, and spectrum purity of DDS output clock signals is improved.

The invention relates to a triangle wave signal generation method and a triangle wave generator. The generator comprises a triangle wave parameter processing unit and a triangle wave generating unit. The triangle wave parameter processing unit is used to process triangle wave parameters to obtain a frequency control word, a time threshold, and an amplitude coefficient. The triangle wave generating unit is used to generate a triangle wave signal according to information obtained by the triangle wave parameter processing unit. The triangle wave generating unit comprises: a phase accumulating module for accumulating the frequency control word once on a rising edge of a clock pulse TC of the triangle wave generating unit to generate a phase code; a comparison module for comparing the phase code and the time threshold obtained by the triangle wave parameter processing unit to generate a triangle wave mark; a selection module determining an output rising edge amplitude coefficient or a falling edge amplitude coefficient in a complement form in a time period according to the triangle wave mark generated by the comparison module; and a multiplication module obtaining the triangle wave signal based on the phase code and the amplitude coefficient output by the selection module.

The invention discloses a direct torque control method based on duty cycle control, which comprises the steps of S1, collecting data of the rotation speed [omega], rotation angle [theta] and three-phase current isa, isb and isc of a motor; S2, converting the three-phase current isa, isb and isc into a rotating coordinate system to obtain current isd and isq; S3, calculating the electromagnetic torque Te, d-axis flux linkage [psi]d, q-axis flux linkage [psi]q and amplitude [psi]s of the stator flux linkage; S4, calculating a sector in which the stator flux linkage is located; S5, calculating areal-time stator flux linkage instruction value, and acquiring a torque reference value according to rotation speed PI control; S6, selecting a voltage vector ui by using a table lookup method; S7, calculating an included angle [theta]psid between the stator flux linkage at the current moment and the d-axis at the action moment; S8, calculating an included angle [theta]ud between the effective voltage vector ui and the d-axis at the action moment according to the selected effective voltage vector ui, the rotation speed [omega]r, the rotation angle [theta]r; and S9, calculating the duty cycle hof the selected effective voltage vector, and calculating the input pulse of each switch tube of an inverter. The direct torque control method improves the calculation method of the duty cycle, and can effectively reduce the amplitude of harmonic components of the torque and rotation speed in a low frequency band.

A multiplex transformer capable of not only suppressing low order harmonic components sufficiently but also suppressing all harmonic components with good balance while suppressing an increase in size of a DC reactor passing a multiplexed DC current. Since the turn ratio of the multiplex transformer (10) is selected to be one that can not only suppress harmonics of a specified order but also suppress all harmonics with good balance and AC reactors (9, 7) are inserted in order to suppress harmonics furthermore, all harmonic components can be suppressed with good balance in addition to sufficient suppression of low order harmonic components while suppressing an increase in size of the DC reactor (3) passing a multiplexed DC current, and not only national regulations but also European regulations can be dealt with.

The invention provides a rotary transformer signal compensation method and device and a rotary transformer. The method comprises steps of obtaining harmonic information of harmonic waves to be compensated in a measured original rotor angle signal; obtaining the actual phase of the to-be-compensated harmonic according to the currently measured angular velocity, the rotor angle compensated in the previous sampling period and the harmonic information of the to-be-compensated harmonic; obtaining a to-be-compensated angle corresponding to the to-be-compensated harmonic according to the actual phaseand amplitude of the to-be-compensated harmonic; finally, performing angle compensation on the original rotor angle signal according to the to-be-compensated angle of each to-be-compensated harmonicwave to obtain compensated rotor angle information, and inputting the compensated rotor angle information into next-stage control as the rotor angle of the motor. According to the scheme, the harmoniccomponent contained in the measured rotor angle signal is compensated to obtain the compensated rotor angle, so that the harmonic component in the rotor angle signal is suppressed, the influence of the harmonic component on the motor control system is avoided, and the performance of the motor control system is improved.

The invention discloses a power regulation device based on controlled silicon. According to the required power, a conduction angle alpha is regulated to be varied in the range of 0-pi, thus the output voltage can be continuously regulated in the range of a second-level voltage and a first-level voltage. The invention can realize continuous regulation of the load voltage value by using the power regulation device based on the controlled silicon and reduce the system oscillation. The fact that the invention can generate smaller harmonic distortion (THDu) compared with the phase-shift power regulation can be discovered by Matlab emulation. The small harmonic distortion (THDu) indicates that harmonic component is restrained and power factors are improved, thereby reducing pollution to power grid.

The invention relates to a grid-connection control policy for a motor train unit grid-side converter under a network voltage fluctuation working condition. A single-phase VSR rotary coordinate system mathematical model is established based on three-phase VSR rotary coordinate system theoretical basis; the problem of delay of a current control internal model is relieved by adopting a rapid virtual axis algorithm; independent regulation on the active power and the reactive power is carried out separately; the mutual coupling problem of the VSR and d and q components is solved by the design of the current inner loop decoupling control; and the harmonic component in the grid-side current is restrained by adopting a carrier phase-shifting technology. According to the grid-connection control policy provided by the invention, the rotary coordinate system based control method and the rapid virtual axis algorithm are adopted, so that static-error-free tracking for the grid current as well as the independent control on the active power and the reactive power can be realized; the problem of delay of the current loop control existing in the pure virtual axis control method is also solved; the dynamic performance of the system is greatly improved; and the harmonic component in the grid-side current is restrained by adopting the carrier phase-shifting technology.

The invention discloses a dynamic element matching method applied to a sigma-delta analog-to-digital converter. The method comprises the following steps of subtracting a feedback DAC signal from an input analog signal, passing a loop filter, and lastly outputting a digital signal through a multi-digit inner quantizer; and processing the digital signal output by the multi-digit inner quantizer through a spin data weighted averaging method firstly and then converting by a digital-to-analog converter to be used as the feedback DAC signal. A dynamic element matching logic circuit is used in the spin data weighted averaging method, and a mismatching error between multi-digit feedback digital-to-analog converter elements is reshaped through the dynamic element matching logic circuit. On the basis of a spin data weighted averaging digital calibration method, the method carries out first-order reshaping on the original relatively-fixed current source mismatching or capacitor mismatching and restrains the harmonic quantity related to the signal, so that the signal-to-noise ratio of the sigma-delta analog-to-digital converter modulator is improved.

The invention discloses a radio-frequency switch circuit. The radio-frequency switch circuit comprises a common terminal and at least two switch branches, wherein the common terminal is used for receiving radio-frequency signals and inputting the radio-frequency signals into the switch branches corresponding to frequencies of the radio-frequency signals, and the switch branches are used for transmitting the radio-frequency signals during connection and suppressing harmonic components of the radio-frequency signals during transmission. The invention further discloses a method of the radio-frequency switch circuit for processing the radio-frequency signals.

The embodiment of the invention provides a mobile terminal and a method for improving call quality, relates to the technical field of communication, and aims to solve the problem that the call qualityis reduced due to the fact that the call function of the mobile terminal is interfered in a charging scene. The charging circuit of the mobile terminal comprises a first switch, an inductor connectedwith the first switch, a second switch, a switch controller and a plurality of capacitors. The second switch comprises an input end and a plurality of output ends, the input end is connected betweenthe first switch and the inductor, the plurality of output ends are in one-to-one correspondence with the plurality of capacitors, and each output end is connected with one end of the corresponding capacitor. The switch controller is connected with the second switch, and the switch controller is used for controlling the input end to be communicated with any output end. And the other ends of the plurality of capacitors are connected in parallel, and the plurality of capacitors are grounded after being connected in parallel. The mobile terminal in the embodiment of the invention is used for a communication scene.

The invention relates to a high-speed non-salient-pole electrically excited synchronous motor rotor in air gap magnetic field sine distribution and a structural parameter determination method of the rotor. Each pole of the rotor includes 2n teeth, the large tooth is arranged in the middle, 2n grooves are distributed in symmetry in the two sides respectively to place excitation windings of the poles, the excitation winding of each pole is formed by connecting n concentric excitation coils of the different turn numbers and pitches in series, and the size of each groove is determined by the number of leads of the groove, as shown in the figure. According to the sine distribution of the air gap magnetic field, the groove number, the pitch and the conductor number of each groove are determined in the principle that the winding turns are distributed in the cosine manner, so that the waveform of the air gap magnetic field approximates to the sine distribution, the harmonic wave component of the magnetic field is reduced, the torque ripple and the vibration noise of the motor are reduced, the loss is reduced, and the motor efficiency is improved. In addition, compared with a salient-pole synchronous motor rotor, the non-salient-pole rotor can greatly improve the highest rotating speed of safe operation, the heat radiation area of the excitation winding can be increased, and the power density of the motor can be improved.

The invention provides the harmonic current restraining method. It provides the changing of the load current value based on the positive, negative cycle, the comparative MCU module is applied to control the opening, breaking estate of the switch setting connecting the two outputs of the bridge rectifier and the accounting empty percentage during the shutting estate, so the restraining harmonic wave, the improving of the power factor and the raise of the direct current side voltage can be realized. The controlling switch is on the state of the cutting during the first controlling time segment t1; the MCU controlling chip controlling switch can conduct the high frequent switch between the state of the shutting and the cutting during the second controlling time section t2; the switch is cutting during the third controlling time section t3, so the current through the loading depresses and the rises, and it can tend to the second peak value current V2 gradually. The MCU controlling chip controlling switch can conduct the high frequent switch between the state of the shutting and the cutting during the four controlling time section t4.

The present invention discloses a three-level rectifier static coordinate system control method. The method comprises four parts consisting of a three-level PWM rectifier main circuit, static coordinate system control, a band-pass filter and a proportion resonant (PR) controller. An outer ring is a voltage ring, a traditional PI (proportional-integral) controller is employed, an inner ring is a current ring, a current instruction value is calculated based on the static coordinate system, and the PR controller is employed. The scheme does not need to perform rotation conversion and phase detection of the power grid voltage and is simple to control. the PR control system including harmonic suppression is employed to effectively inhibit the harmonic component of current at an alternating current side. The three-level rectifier static coordinate system control method realizes stable direct current voltage output and current sine input of the three-level rectifier when the power grid voltage generates single-phase dropping and there is harmonic wave.

The invention discloses a broadband VCO based on a source damping resistor. The broadband VCO belongs to the field of radio frequency integrated circuits and comprises LC-VCO cores of N working frequency bands, and N is an integer greater than or equal to 2; each LC-VCO core comprises an NMOS pair and a PMOS pair of which grid electrodes and drain electrodes are in cross coupling connection, a resonance network formed by connecting a switched capacitor array C-Tank, a variable capacitor and an L-C resonance network in parallel, and a source electrode damping resistor which is independently orsimultaneously connected with the source ends of the NMOS pair / PMOS pair, wherein drain electrodes of the NMOS pair and the PMOS pair are connected and then are connected with the resonance network; the L-C resonance network is used for carrying out frequency selection on an output signal and selecting a concerned fundamental frequency, the L-C resonance network comprises an inductor L and a capacitor C, and different LC-VCO cores have different inductors L and capacitors C. The source damping resistor is used for realizing loop gain reduction, designing an 8-shaped customized inductor, increasing the Q value of a resonant cavity, inhibiting harmonic components generated by a nonlinear effect, reducing flicker noise transmission and optimizing the phase noise performance of a VCO output signal.

The invention discloses a control method, apparatus, and equipment of a PFC circuit, and a storage medium. The control method comprises: obtaining an alternating current error parameter in the PFC circuit; performing proportional-integral resonant control on the alternating current error parameter, and obtaining a PWM parameter according to a control result; and controlling a switch tube in the PFC circuit according to the PWM parameter. By employing the control method, the technical problem of failure of accurate realization of a current loop control process during control of the PFC circuit can be solved.

The invention discloses a three-dimensional wound iron core three-phase dry-type transformer for a nuclear station. The transformer comprises a supporting frame as well as clamp pieces, three-dimensional wound iron cores and coils, which form a transformer main body, wherein the three-dimensional wound iron cores are arranged in triangular shapes and wound with the coils respectively to form three-phase structures; the clamp pieces comprise upper clamp pieces and lower clamp pieces; the triangular structures of the three-dimensional wound iron cores are fixed with the lead wires of the coils through the upper clamp pieces and the lower clamp pieces; the supporting frame comprises a frame base and an anti-seismic bracket; the transformer main body is mounted and fixed on the frame base; the anti-seismic bracket is arranged between the transformer main body and the frame base. The anti-seismic bracket is configured on the basis of the three-dimensional triangular structure, is also of the triangular structure and is used for supporting the three side surfaces of the transformer main body, so that the whole transformer can be kept stable when being stressed in different directions, the anti-seismic capability of the transformer is greatly improved, and the safety level of the transformer is higher.

The invention discloses a Doherty amplifier with defected ground structures. The Doherty amplifier comprises a signal separator, a main amplification circuit, at least one auxiliary amplification circuit and a signal combiner; the signal separator separates input signals and then sends the separated input signals to the main amplification circuit and the auxiliary amplification circuits; the mainamplification circuit and the auxiliary amplification circuits amplify the signals separated by the signal separator respectively and then input the amplified signals to the signal combiner; the signal combiner combines the signals amplified by the main amplification circuit and the auxiliary amplification circuits and then outputs the combined signals; each auxiliary amplification circuit comprises a peak value amplifier, and the lower portion of a transmission line of an output end of each peak value amplifier is provided with a first defected ground structure. According to the Doherty amplifier with the defected ground structures, the lower portions of the transmission lines of the output ends of the peak value amplifiers are provided with the first defected ground structure, so that the harmonic component of the output signals of the auxiliary amplification circuits is inhibited, and the output power, power added efficiency and linearity of the Doherty amplifier are improved; meanwhile, through the arrangement of the first defected ground structures, the circuit size can be reduced, and the manufacturing cost is lowered.

The invention discloses a capacitive linear displacement sensor and a movable ruler thereof, the movable ruler comprises a movable ruler base body and an induction electrode, the induction electrode has a three-measuring-head or four-measuring-head structural form, the sensor comprises a fixed ruler and the movable ruler, the fixed ruler comprises a fixed ruler base body and an excitation electrode. The A-phase excitation signal lead and the C-phase excitation signal lead of the excitation electrode form a twisted pair on one side of the excitation electrode, and the B-phase excitation signal lead and the D-phase excitation signal lead form a twisted pair on the other side of the excitation electrode. The twisted pair structure can eliminate lead crosstalk, thereby reducing the influence of interference signals on the measurement precision, and ensuring the measurement precision. The three-measuring-head or four-measuring-head structural form can improve the area utilization rate of the sensing electrode and increase the coupling capacitance value, so that the signal-to-noise ratio is improved, data fusion is carried out on output signals of the sensing electrode, some harmonic errors of specific frequencies can be effectively eliminated, and the measurement precision is further improved.

The invention discloses a high-voltage electric field low-temperature plasma cold sterilization system circuit and device, and belongs to the technical field of frequency converter power circuits. Thehigh-voltage electric field low-temperature plasma cold sterilization system circuit comprises a power module used for outputting harmonic currents, a voltage regulating module used for regulating the load voltage, the load current and the load power, a switch module used for regulating the on-off state of the circuit and a transformer power supply module used for generating high voltage, whereinthe power module comprises a single-phase frequency converter and a first-stage inductor; the frequency converter comprises an input end and two output ends, the input end is connected with an alternating-current power supply, and the output ends are connected with the voltage regulating module; and the inductor is connected between the output ends of the frequency converter and a voltage regulator in series, so that the function of an electric reactor is achieved, harmonic components in SPWM waves output by the frequency converter are effectively restrained, the frequency spectrum is broadened, the harmonic currents entering the voltage regulating module are stable, the heating loss of the voltage regulating module is reduced, and the voltage regulating module is prevented from being burnt down.

The invention discloses a bearing fault diagnosis method adopting current signal analysis under a rotating speed fluctuation quasi-stable working condition. The method comprises the following steps of: firstly, respectively connecting corresponding quasi-resonance compensators in a current loop and a rotating speed loop of a vector control system in parallel to suppress a current measurement error and a current harmonic component caused by nonlinearity of an inverter, and secondly, designing an optimal band-pass filter by utilizing a fast spectral kurtosis algorithm to extract a transient impact fault component of a current signal; and then, extracting a square envelope line of the filtered current signal by adopting Hilbert transform, and further solving a square envelope spectrum by using discrete Fourier transform to realize accurate extraction of the fault feature component of the permanent magnet synchronous bearing. According to the method, motor current signal characteristic analysis is adopted, and meanwhile, the high gain and wide bandwidth characteristics of the quasi-resonance controller are utilized, so that the fault diagnosis of the permanent magnet synchronous motor bearing under the rotating speed fluctuation quasi-stable working condition can be realized.

The invention discloses a high-voltage electric field low-temperature plasma cold sterilization device, and belongs to the technical field of frequency converter power supply circuits. According to the high-voltage electric field low-temperature plasma cold sterilization device, a frequency converter, a first-stage inductor, an electric voltage regulator, an alternating-current contactor and a solid-state relay are arranged on the front portion in a shell, a transformer is arranged on the rear portion of the shell, the transformer with a large size is arranged on the inner side of the shell, and the frequency converter, the first-stage inductor, the electric voltage regulator, a second-stage inductor, the alternating current contactor and the solid-state relay which are small in size are located on the outer side of the shell, so that mounting and dismounting are convenient, and the working conditions of all structures can be observed conveniently. The frequency converter is externallyconnected with the first-stage inductor, so that the output voltage is controllable, harmonic components in modulation waves are suppressed, the frequency spectrum is expanded, and the harmonic current entering a voltage regulation module is stable.

The invention discloses a sine and cosine position encoder suitable for a stator non-magnetic-rail type linear motor. The sine and cosine position encoder comprises an installation support, an iron core, an excitation coil and a response coil. According to the main structure of the position encoder, the iron core, the exciting coil and the response coil are combined to form a position encoder bodyand fixed to an installation support, the body is installed in the vertical direction of a stator of the stator non-magnetic-rail type linear motor, and a certain air gap is reserved between the bodyand the stator of the stator non-magnetic-rail type linear motor. According to the working principle, after an excitation signal is input into the excitation coil, the iron core and the stator of thestator non-magnetic-rail type linear motor interact in the motor advancing process, magnetic flux density similar to sine change is generated, and then a response signal is generated in the responsecoil. And the response coil is connected in series or in parallel to reconstruct a response signal to obtain mutually orthogonal sine and cosine signals so as to reflect the real-time rotor position of the stator non-magnetic-rail type linear motor. The position encoder has the advantages of small size, reliable structure, high precision, low cost and the like.