To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors,the temperature rise of various components in the motor is analyzed by coupling the ...To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors,the temperature rise of various components in the motor is analyzed by coupling the equivalent thermal circuit method and computational fluid dynamics.Also,a cooling strategy is proposed to solve the problem of temperature rise,which is expected to prolong the service life of these devices.First,the theoretical bases of the approaches used to study heat transfer and fluid mechanics are discussed,then the fluid flow for the considered motor is analyzed,and the equivalent thermal circuit method is introduced for the calculation of the temperature rise.Finally,the stator,rotor loss,motor temperature rise,and the proposed cooling method are also explored through experiments.According to the results,the stator temperature at 50,000 r/min and 60,000 r/min at no-load operation is 68℃ and 76℃,respectively.By monitoring the temperature of the air outlets inside and outside the motor at different speeds,it is also found that the motor reaches a stable temperature rise after 65 min of operation.Coupling of the thermal circuit method and computational fluid dynamics is a strategy that can provide the average temperature rise of each component and can also comprehensively calculate the temperature of each local point.We conclude that a hybrid cooling strategy based on axial air cooling of the inner air duct of the motor and water cooling of the stator can meet the design requirements for the ventilation and cooling of this type of motors.展开更多
Magnetic shielding is very important in the design of a high-power dc comparator. This paper addressed the application of magnetic circuit method to calculate the magnetic shielding effectiveness of high-power dc comp...Magnetic shielding is very important in the design of a high-power dc comparator. This paper addressed the application of magnetic circuit method to calculate the magnetic shielding effectiveness of high-power dc comparators when an external radial magnetic field is added. The mathematical relationship between the magnetic shielding effectiveness and the parameters of the magnetic shielding body were obtained. To verify the validity of the calculation method, we developped a procedure to measure the magnetic shielding effectiveness of the magnetic body by measuring the induction voltage of the detection winding instead of the magnetic intensity at a point in the magnetic shielding body, making the manipulation much easier. The result calculated with the magnetic circuit method turns out to be closer to the measured one compared with that calculated with a conventional algorithm proposed by Ren, suggesting that the magnetic circuit method is an applicable tool for estimating the toroidal cavity magnetic shielding effectiveness of a heavy current comparator when a radial magnetic field is added.展开更多
The objective in this presentation is to introduce some of the unique properties and applications of nullors in active circuit analysis and designs. The emphasis is to discuss the role nullors can play in symbolic rep...The objective in this presentation is to introduce some of the unique properties and applications of nullors in active circuit analysis and designs. The emphasis is to discuss the role nullors can play in symbolic representation of transfer functions. To show this we adopt the topological platform for the circuit analysis and use a recently developed Admittance Method (AM) to achieve the Sum of Tree Products (STP), replacing the determinant and cofactors of the Nodal Admittance Matrix (NAM) of the circuit. To construct a transfer function, we start with a given active circuit and convert all its controlled sources and I/O-ports to nullors. Now, with a solid nullor circuit (passive elements and nullors) we first eliminate the passive elements through AM operations. This produces the STPs. Second, the all-nullor circuit is then used to find the signs or the STPs. Finally, the transfer function (in symbolic, if chosen) is obtained from the ratio between the STPs.展开更多
Magnetoelectric equivalent circuit analytical method is presented for laminate composites of magneto- strictive Terfenol-D (TbxDy1-xFe2) and piezoelectric Pb(Zr1-xTix)O3 (PZT) operated in longitudinal mag- netized and...Magnetoelectric equivalent circuit analytical method is presented for laminate composites of magneto- strictive Terfenol-D (TbxDy1-xFe2) and piezoelectric Pb(Zr1-xTix)O3 (PZT) operated in longitudinal mag- netized and transverse polarized (or L-T), and transverse magnetized and transverse polarized (or T-T) modes. Magnetoelectric (ME) couplings both at low-frequency and resonance-frequency have been studied, and our analysis predicts that (i) the ME voltage coefficients of both L-T and T-T modes in- crease with increasing the thickness of the piezoelectric phase whereas magnetostrictive phase thickness keeps constant, and then tend to saturation when the thickness ratio of piezoelectric phase to magnetic phases is >3; (ii) there are the optimum thickness ratios that maximize magnetoelectric (ME) voltage coefficients for the two modes, which are dependent on elastic compliances ratio of piezoelec- tric phase and magnetostrictive phase; and (iii) the ME voltage coefficients are dramatically increased by a factor of ~Qm, when operated at resonance frequency. A series of Terfenol-D/PZT laminates were fabricated, and the results were compared with the theoretical ones. Experiments confirmed that equivalent circuit method is a useful tool for optimum designs of ME laminates.展开更多
A new method for analyzing high-speed circuit systems is presented. The method adds transmission line end currents to the circuit variables of the classical modified nodal approach. Then the matrix equation describing...A new method for analyzing high-speed circuit systems is presented. The method adds transmission line end currents to the circuit variables of the classical modified nodal approach. Then the matrix equation describing high-speed circuit system can be formulated directly and analyzed conveniently for its normative form. A time-domain analysis method for transmission lines is also introduced. The two methods are combined together to efficiently analyze high-speed circuit systems having general transmission lines. Numerical experiment is presented and the results are compared with that calculated by Hspice.展开更多
This paper presents an analytical method for electromagnetic acoustic transducers (EMATs) under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs inc...This paper presents an analytical method for electromagnetic acoustic transducers (EMATs) under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs including the non-uniform biased magnetic field, a pulsed eddy current field and the acoustic field is built up. The pulsed voltage excitation is transformed to the frequency domain by fast Fourier transformation (FFT). In terms of the time harmonic field equations of the EMAT system, the impedances of the coils under different frequencies are calculated according to the circuit-field coupling method and Poynting's theorem. Then the currents under different frequencies are calculated according to Ohm's law and the pulsed current excitation is obtained by inverse fast Fourier transformation (IFFT). Lastly, the sequentially coupled finite element method (FEM) is used to calculate the Lorentz force in the EMATs under the current excitation. An actual EMAT with a two-layer two-bundle printed circuit board (PCB) coil, a rectangular permanent magnet and an aluminium specimen is analysed. The coil impedances and the pulsed current are calculated and compared with the experimental results. Their agreement verified the validity of the proposed method. Further- more, the influences of lift-off distances and the non-uniform static magnetic field on the Lorentz force under pulsed voltage excitation are studied.展开更多
Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application...Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application environment and topological structure and operating principles of hybrid circuit breakers, and key stress parameters in transient state process of two time dimensions are extracted. The established digital simulation circuit for PSCAD/EMTDC device-level operation of the circuit breaker has verified the stress properties of millisecond level breaking process and microsecond level commutation process. Then, equivalent test method, circuits and parameters based on LC power supply are proposed on the basis of stress extraction. Finally, the results of implemented breaking tests for complete 200 kV circuit breaker, 100 kV and 50 kV circuit breaker units, as well as single power electronic module have verified the accuracy of the simulation circuit and mathematical analysis. The result of this paper can be a guide to electrical structure and test system design of hybrid HVDC circuit breaker.展开更多
Instead of normally tackling electric circuits by virtue of the Kirchhoff's theorem whose aim is to derive voltage,electric current, and electric impedence, our aim in this paper is to derive the characteristic fr...Instead of normally tackling electric circuits by virtue of the Kirchhoff's theorem whose aim is to derive voltage,electric current, and electric impedence, our aim in this paper is to derive the characteristic frequency of a three-loop mesoscopic LC circuit with three mutual inductances, e.g., for the radiating frequency of the three-loop LC oscillator, we adopt the invariant eigen-operator(IEO) method to realize our aim.展开更多
This paper introduced the basic theory and algorithm of the surrogate data method,which proposed a rigorous way to detect the random and seemingly stochastic characteristics in a system.The Gaussian data and the Rossl...This paper introduced the basic theory and algorithm of the surrogate data method,which proposed a rigorous way to detect the random and seemingly stochastic characteristics in a system.The Gaussian data and the Rossler data were used to show the availability and effectivity of this method.According to the analysis by this method based on the short-circuiting current signals under the conditions of the same voltage and different wire feed speeds,it is demonstrated that the electrical signals time series exhibit apparently randomness when the welding parameters do not match.However,the electrical signals time series are deterministic when a match is found.The stability of short-circuiting transfer process could be judged exactly by the method of surrogate data.展开更多
The increasing use of color terminals for personal computers has raised a demand for video graphic adapter(VGA)-format panel displays. Since only monochrome(ZnS∶Mn) electroluminescence(EL) displays of suitable size a...The increasing use of color terminals for personal computers has raised a demand for video graphic adapter(VGA)-format panel displays. Since only monochrome(ZnS∶Mn) electroluminescence(EL) displays of suitable size and speed are available, lack of colors has to be replaced by grayscale in the first place. There are two basic driving methods to achieve grayscale in thin-film EL displays: pulse amplitude modulation(PAM) method and pulse width modulation(PWM) method. But there are serious disadvantages of the two traditional methods. For the former method, the high voltage PAM ICs are too expensive to produce the grayscale EL display in bulks and the driver integrated circuit(IC) is complex. Though the PWM method has good grayscale display quality, the hardware implementation is too complex. A new driving method with which the width and the amplitude of the pulse can be modulated and simultaneously the challenge can be solved efficaciously is presented.展开更多
Symbolic analysis has many applications in the design of analog circuits. Existing approaches rely on two forms of symbolic-expression representation: expanded sum-of-product form and arbitrarily nested form. Expanded...Symbolic analysis has many applications in the design of analog circuits. Existing approaches rely on two forms of symbolic-expression representation: expanded sum-of-product form and arbitrarily nested form. Expanded form suffers the problem that the number of product terms grows exponentially with the size of a circuit. Nested form is neither canonical nor amenable to symbolic manipulation. In this paper, we present a new approach to exact and canonical symbolic analysis by exploiting the sparsity and sharing of product terms. This algorithm, called totally coded method (TCM), consists of representing the symbolic determinant of a circuit matrix by code series and performing symbolic analysis by code manipulation. We describe an efficient code-ordering heuristic and prove that it is optimum for ladder-structured circuits. For practical analog circuits, TCM not only covers all advantages of the algorithm via determinant decision diagrams (DDD) but is more simple and efficient than DDD method.展开更多
Reducing the power and energy required by the device/circuit to operate is the main aim of this paper. Here the new design is implemented to reduce the power consumption of the device using the triggering pulses. The ...Reducing the power and energy required by the device/circuit to operate is the main aim of this paper. Here the new design is implemented to reduce the power consumption of the device using the triggering pulses. The proposed triggering method uses a complementary MOS transistor (pMOS and nMOS) as a voltage divider and ground leakage suppressor (i.e.);these designs are named as Trig01 and Trig10 designs. In Trig01 design the pair of CMOS is placed in the voltage divider part;similarly in Trig10 design the pair of CMOS is placed at the ground leakage suppressor part. Standard CMOS gates like NOT, NAND, NOR, EX-OR etc. are designed with these technologies and these gates are designed with 180 nm technology file in the cadence tool suite;compared to the normal CMOS gates, the Bi-Trig gate contains 4 inputs and 2 outputs. The two extra inputs are used as Bi-Trig control signaling inputs. There are 2 control inputs and thus 2<sup>2</sup> = 4 combination of controlling is done (i.e.);both pMOS and nMOS are ON, both pMOS and nMOS are OFF, pMOS ON and nMOS OFF and pMOS ON and nMOS ON. Depending on the usage of the circuit, the mode of operation is switched to any one of the combination. If the output of the circuit is not used anywhere in the total block, that specified circuit can be switched into idle mode by means of switched OFF both the pMOS and nMOS transistor in the control unit. This reduces the leakage current and also the power wastage of the circuits in the total block. Bi-Trig controlled circuit reduces the power consumption and leakage power of the circuit without affecting a performance of the circuits.展开更多
Presented field-circuit coupled adaptive time-stepping finite element method to study on permanent magnet linear synchronous motor (PMLSM) characteristics fed by SPWM voltage source inverter.In air-gap field where the...Presented field-circuit coupled adaptive time-stepping finite element method to study on permanent magnet linear synchronous motor (PMLSM) characteristics fed by SPWM voltage source inverter.In air-gap field where the direction or magnitude of the field is changing rapidly,the smallest elements are demanded due to high accuracy to use adaptive meshing technique.The co-simulation was used with the status space functions and time-step finite element functions,in which time-step of the status space functions was the smallest than finite element functions'.The magnitude relation of the normal elec- tromagnetic force and tangential electromagnetic force and the period were attained,and current curve was very abrupt at current zero area due to the bigger resistance and leak- age reactance,including main characteristics of motor voltage and velocity.The simulation results compare triumphantly with the experiments results.展开更多
文摘To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors,the temperature rise of various components in the motor is analyzed by coupling the equivalent thermal circuit method and computational fluid dynamics.Also,a cooling strategy is proposed to solve the problem of temperature rise,which is expected to prolong the service life of these devices.First,the theoretical bases of the approaches used to study heat transfer and fluid mechanics are discussed,then the fluid flow for the considered motor is analyzed,and the equivalent thermal circuit method is introduced for the calculation of the temperature rise.Finally,the stator,rotor loss,motor temperature rise,and the proposed cooling method are also explored through experiments.According to the results,the stator temperature at 50,000 r/min and 60,000 r/min at no-load operation is 68℃ and 76℃,respectively.By monitoring the temperature of the air outlets inside and outside the motor at different speeds,it is also found that the motor reaches a stable temperature rise after 65 min of operation.Coupling of the thermal circuit method and computational fluid dynamics is a strategy that can provide the average temperature rise of each component and can also comprehensively calculate the temperature of each local point.We conclude that a hybrid cooling strategy based on axial air cooling of the inner air duct of the motor and water cooling of the stator can meet the design requirements for the ventilation and cooling of this type of motors.
基金Funded by the Natural Science Foundation of China under the grant number 50277018.
文摘Magnetic shielding is very important in the design of a high-power dc comparator. This paper addressed the application of magnetic circuit method to calculate the magnetic shielding effectiveness of high-power dc comparators when an external radial magnetic field is added. The mathematical relationship between the magnetic shielding effectiveness and the parameters of the magnetic shielding body were obtained. To verify the validity of the calculation method, we developped a procedure to measure the magnetic shielding effectiveness of the magnetic body by measuring the induction voltage of the detection winding instead of the magnetic intensity at a point in the magnetic shielding body, making the manipulation much easier. The result calculated with the magnetic circuit method turns out to be closer to the measured one compared with that calculated with a conventional algorithm proposed by Ren, suggesting that the magnetic circuit method is an applicable tool for estimating the toroidal cavity magnetic shielding effectiveness of a heavy current comparator when a radial magnetic field is added.
文摘The objective in this presentation is to introduce some of the unique properties and applications of nullors in active circuit analysis and designs. The emphasis is to discuss the role nullors can play in symbolic representation of transfer functions. To show this we adopt the topological platform for the circuit analysis and use a recently developed Admittance Method (AM) to achieve the Sum of Tree Products (STP), replacing the determinant and cofactors of the Nodal Admittance Matrix (NAM) of the circuit. To construct a transfer function, we start with a given active circuit and convert all its controlled sources and I/O-ports to nullors. Now, with a solid nullor circuit (passive elements and nullors) we first eliminate the passive elements through AM operations. This produces the STPs. Second, the all-nullor circuit is then used to find the signs or the STPs. Finally, the transfer function (in symbolic, if chosen) is obtained from the ratio between the STPs.
基金Supported by the Office of Naval Research in USA
文摘Magnetoelectric equivalent circuit analytical method is presented for laminate composites of magneto- strictive Terfenol-D (TbxDy1-xFe2) and piezoelectric Pb(Zr1-xTix)O3 (PZT) operated in longitudinal mag- netized and transverse polarized (or L-T), and transverse magnetized and transverse polarized (or T-T) modes. Magnetoelectric (ME) couplings both at low-frequency and resonance-frequency have been studied, and our analysis predicts that (i) the ME voltage coefficients of both L-T and T-T modes in- crease with increasing the thickness of the piezoelectric phase whereas magnetostrictive phase thickness keeps constant, and then tend to saturation when the thickness ratio of piezoelectric phase to magnetic phases is >3; (ii) there are the optimum thickness ratios that maximize magnetoelectric (ME) voltage coefficients for the two modes, which are dependent on elastic compliances ratio of piezoelec- tric phase and magnetostrictive phase; and (iii) the ME voltage coefficients are dramatically increased by a factor of ~Qm, when operated at resonance frequency. A series of Terfenol-D/PZT laminates were fabricated, and the results were compared with the theoretical ones. Experiments confirmed that equivalent circuit method is a useful tool for optimum designs of ME laminates.
文摘A new method for analyzing high-speed circuit systems is presented. The method adds transmission line end currents to the circuit variables of the classical modified nodal approach. Then the matrix equation describing high-speed circuit system can be formulated directly and analyzed conveniently for its normative form. A time-domain analysis method for transmission lines is also introduced. The two methods are combined together to efficiently analyze high-speed circuit systems having general transmission lines. Numerical experiment is presented and the results are compared with that calculated by Hspice.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10974115)
文摘This paper presents an analytical method for electromagnetic acoustic transducers (EMATs) under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs including the non-uniform biased magnetic field, a pulsed eddy current field and the acoustic field is built up. The pulsed voltage excitation is transformed to the frequency domain by fast Fourier transformation (FFT). In terms of the time harmonic field equations of the EMAT system, the impedances of the coils under different frequencies are calculated according to the circuit-field coupling method and Poynting's theorem. Then the currents under different frequencies are calculated according to Ohm's law and the pulsed current excitation is obtained by inverse fast Fourier transformation (IFFT). Lastly, the sequentially coupled finite element method (FEM) is used to calculate the Lorentz force in the EMATs under the current excitation. An actual EMAT with a two-layer two-bundle printed circuit board (PCB) coil, a rectangular permanent magnet and an aluminium specimen is analysed. The coil impedances and the pulsed current are calculated and compared with the experimental results. Their agreement verified the validity of the proposed method. Further- more, the influences of lift-off distances and the non-uniform static magnetic field on the Lorentz force under pulsed voltage excitation are studied.
基金supported by SGCC Scientific and Technological Project(52110116004W)
文摘Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application environment and topological structure and operating principles of hybrid circuit breakers, and key stress parameters in transient state process of two time dimensions are extracted. The established digital simulation circuit for PSCAD/EMTDC device-level operation of the circuit breaker has verified the stress properties of millisecond level breaking process and microsecond level commutation process. Then, equivalent test method, circuits and parameters based on LC power supply are proposed on the basis of stress extraction. Finally, the results of implemented breaking tests for complete 200 kV circuit breaker, 100 kV and 50 kV circuit breaker units, as well as single power electronic module have verified the accuracy of the simulation circuit and mathematical analysis. The result of this paper can be a guide to electrical structure and test system design of hybrid HVDC circuit breaker.
基金Project supported by the National Natural Science Foundation of China(Grant No.11775208)
文摘Instead of normally tackling electric circuits by virtue of the Kirchhoff's theorem whose aim is to derive voltage,electric current, and electric impedence, our aim in this paper is to derive the characteristic frequency of a three-loop mesoscopic LC circuit with three mutual inductances, e.g., for the radiating frequency of the three-loop LC oscillator, we adopt the invariant eigen-operator(IEO) method to realize our aim.
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.51205283)
文摘This paper introduced the basic theory and algorithm of the surrogate data method,which proposed a rigorous way to detect the random and seemingly stochastic characteristics in a system.The Gaussian data and the Rossler data were used to show the availability and effectivity of this method.According to the analysis by this method based on the short-circuiting current signals under the conditions of the same voltage and different wire feed speeds,it is demonstrated that the electrical signals time series exhibit apparently randomness when the welding parameters do not match.However,the electrical signals time series are deterministic when a match is found.The stability of short-circuiting transfer process could be judged exactly by the method of surrogate data.
文摘The increasing use of color terminals for personal computers has raised a demand for video graphic adapter(VGA)-format panel displays. Since only monochrome(ZnS∶Mn) electroluminescence(EL) displays of suitable size and speed are available, lack of colors has to be replaced by grayscale in the first place. There are two basic driving methods to achieve grayscale in thin-film EL displays: pulse amplitude modulation(PAM) method and pulse width modulation(PWM) method. But there are serious disadvantages of the two traditional methods. For the former method, the high voltage PAM ICs are too expensive to produce the grayscale EL display in bulks and the driver integrated circuit(IC) is complex. Though the PWM method has good grayscale display quality, the hardware implementation is too complex. A new driving method with which the width and the amplitude of the pulse can be modulated and simultaneously the challenge can be solved efficaciously is presented.
文摘Symbolic analysis has many applications in the design of analog circuits. Existing approaches rely on two forms of symbolic-expression representation: expanded sum-of-product form and arbitrarily nested form. Expanded form suffers the problem that the number of product terms grows exponentially with the size of a circuit. Nested form is neither canonical nor amenable to symbolic manipulation. In this paper, we present a new approach to exact and canonical symbolic analysis by exploiting the sparsity and sharing of product terms. This algorithm, called totally coded method (TCM), consists of representing the symbolic determinant of a circuit matrix by code series and performing symbolic analysis by code manipulation. We describe an efficient code-ordering heuristic and prove that it is optimum for ladder-structured circuits. For practical analog circuits, TCM not only covers all advantages of the algorithm via determinant decision diagrams (DDD) but is more simple and efficient than DDD method.
文摘Reducing the power and energy required by the device/circuit to operate is the main aim of this paper. Here the new design is implemented to reduce the power consumption of the device using the triggering pulses. The proposed triggering method uses a complementary MOS transistor (pMOS and nMOS) as a voltage divider and ground leakage suppressor (i.e.);these designs are named as Trig01 and Trig10 designs. In Trig01 design the pair of CMOS is placed in the voltage divider part;similarly in Trig10 design the pair of CMOS is placed at the ground leakage suppressor part. Standard CMOS gates like NOT, NAND, NOR, EX-OR etc. are designed with these technologies and these gates are designed with 180 nm technology file in the cadence tool suite;compared to the normal CMOS gates, the Bi-Trig gate contains 4 inputs and 2 outputs. The two extra inputs are used as Bi-Trig control signaling inputs. There are 2 control inputs and thus 2<sup>2</sup> = 4 combination of controlling is done (i.e.);both pMOS and nMOS are ON, both pMOS and nMOS are OFF, pMOS ON and nMOS OFF and pMOS ON and nMOS ON. Depending on the usage of the circuit, the mode of operation is switched to any one of the combination. If the output of the circuit is not used anywhere in the total block, that specified circuit can be switched into idle mode by means of switched OFF both the pMOS and nMOS transistor in the control unit. This reduces the leakage current and also the power wastage of the circuits in the total block. Bi-Trig controlled circuit reduces the power consumption and leakage power of the circuit without affecting a performance of the circuits.
基金National Natural Sciences Foundation(60474043)Henan Province Science Fund for Distinguished Young Scholars(0412002200)Henan Province Major Projects(0223025300)
文摘Presented field-circuit coupled adaptive time-stepping finite element method to study on permanent magnet linear synchronous motor (PMLSM) characteristics fed by SPWM voltage source inverter.In air-gap field where the direction or magnitude of the field is changing rapidly,the smallest elements are demanded due to high accuracy to use adaptive meshing technique.The co-simulation was used with the status space functions and time-step finite element functions,in which time-step of the status space functions was the smallest than finite element functions'.The magnitude relation of the normal elec- tromagnetic force and tangential electromagnetic force and the period were attained,and current curve was very abrupt at current zero area due to the bigger resistance and leak- age reactance,including main characteristics of motor voltage and velocity.The simulation results compare triumphantly with the experiments results.