The acceleration and deceleration rate of the train depend on the tractive force. When the wheels of the train slip on the rails, the torque is decreased to avoid the continuous slipping. This reason is that the tractive coefficient between the wheels and the rails has a peak at a certain slip velocity. But this adhesive phenomenon is not clearly examined or analyzed.Thus we have developed a new tractive test equipment. In this paper, we measured the tractive force with this equipment, and clarified the adhesive phenomenon. Then we proposed a new tractive force control and verified theeffectiveness of the proposed control scheme.
This paper deals with a digital control scheme of multiple paralleled high frequency switching current amplifier with four-quadrant chopper for generating gradient magnetic fields in MRI (Magnetic Resonance Imaging) systems. In order to track high precise current pattern in Gradient Coils (GC), the proposal current amplifier cancels the switching current ripples in GC with each other and designed optimum switching gate pulse patterns without influences of the large filter current ripple amplitude. The optimal control implementation and the linear control theory in GC current amplifiers have affinity to each other with excellent characteristics. The digital control system can be realized easily through the digital control implementation, DSPs or microprocessors. Multiple-parallel operational microprocessors realize two or higher paralleled GC current pattern tracking amplifier with optimal control design and excellent results are given for improving the image quality of MRI systems.
State-of-the-art Internet technologies allow us to provide advanced and interactive distance education services. However, we could not help but gather students for experiments and exercises in an education for engineering because large-scale equipments and expensive software are required. On the other hand, teleoperation systems with robot manipulator or vehicle via Internet have been developed in the field of robotics. By fusing these two techniques, we can realize remote experiment and exercise systems for the engineering education based on World Wide Web. This paper presents how to construct the remote environment that allows students to take courses on experiment and exercise independently of their locations. By using the proposed system, users can exercise and practice remotely about control of a manipulator and a robot vehicle and programming of image processing.
The d-axis inductance of reluctance motor is affected by not only the d-axis current but also the q-axis current, because of cross magnetic saturation between the direct and quadrature axes. This situation is similar for the q-axis inductance. The authors propose a method to determine the d-axis inductance related to the d- and q-axis currents and the q-axis inductance related to the d- and q-axis currents from a standstill test. This method involves the following four steps. First a rectangular-wave voltage, alternated between plus and minus, is applied to the two armature winding terminals after braking the rotor in the d-axis position. Secondly the voltage and current between the terminals are measured. Thirdly the d-axis inductance related with d-axis current is calculated from the voltage and current. Finally the process above is repeated when a DC current flows from the remaining armature terminal to neutral point terminal and the d-axis inductance related to the d- and q-axis currents is derived. A similar treatment applies when determining the q-axis inductance related to the d-and q-axis currents in the q-axis rotor position. The method is implemented on a 1.1kW-178V- 6.3A-4P-2200min-1 flux barrier type reluctance motor. Results of load performance on a vector controlled reluctance motor measured by on-load tests and calculated from the d- and q-axis inductances obtained by the proposed method clearly demonstrate the validity of the proposed method.
The The development of advanced Insulated Gate Bipolar Transistor (IGBT) has enabled high-frequency switching operation and has improved the performance of PWM inverters for motor drive. However, the high rate of dv/dt of IGBT has adverse effects on motor insulation stress. In many motor drive applications, the inverter and motor are separated and it requires long motor feds. The long cable contributes high frequency ringing at the motor terminal and it results in high surge voltage which stresses the motor insulation. The inverter output filter and RDC snubber are conventional method which can reduce the surge voltage. In this paper, we propose the new low loss snubber to reduce the motor terminal surge voltage. The snubber consists of the series connection of charging/discharging capacitor and the voltage-clamped capacitor. At IGBT turn-off, the snubber starts to operate when the IGBT voltage reaches the voltage-clamped level. Since dv/dt is decreased by snubber operating, the peak level of the surge voltage can be reduced. Also the snubber operates at the IGBT voltage above the voltage-clamped level, the snubber loss is largely reduced comparing with RDC snubber. The proposed snubber enables to reduce the motor terminal surge voltage with low loss.
In the proposed adhesion control methods with sensors, the wheel speed is required for the tractive force estimation.However, in the railway field, the pulse generator (PG) used forthe wheel speed measurement is attached on the main motor and with only 60 pulse-per-revolution (ppr).Therefore, when the train is in the low-speed region, the speed value cannot be obtained in each control period.To solve this problem, the adhesion control in low-speed region with considering the low-resolution PG is proposed in this paper.In this control method, a disturbance-instantaneous-speed observer is designedto (1) estimate the instantaneous wheel speed from the motor torque and the corrected tractive torque, (2) correct the estimated tractive torque when the real speed signalis measured from PG.The simulation and experiment verification results of the effectiveness of the proposed adhesion control with the instantaneous wheel speed estimation are reported.
A shaft generator system, which consists of a shaft generator, a rectifier, an externally commutated thyristor inverter, an ac reactor, and a synchronous compensator, is widely used in a ship to feed sufficient power to the electric apparatus by using a part of the power produced by the main engine. We have already analyzed the steady-state performances of this type of generating system in some detail. However, transient characteristics of the shaft generator system have been investigated little. In this paper, transient performances of the shaft generator system are analyzed in detail. A set of transient equations is derived first for the systems with ordinary ac reactor or duplex reactor to achieve output voltage without distortion, and a block diagram representation of the equations is then obtained. Transient responses of the system when the load was changed are calculated through the diagram and compared with experimental results. Also, the block diagram is modified to take the effects of the magnetic-saturation phenomenon of synchronous compensator into account to obtain an accurate simulated result. Moreover, the effects of the duplex reactor and inertia constant of synchronous compensator on the transient responses are clarified for the cases when various system variables are changed.
This paper proposes a series active filter for mitigation of the 3rd-harmonic voltage in a three-phase four-wire power distribution system in a building.The active filter which consists of a single-phase inverter can suppress the harmonic voltage of the system. The active filter is characterized by acting not only as a capacitor but also as a resistor for the 3rd-harmonic components. A Hilbert transformer is applied to the controller of the active filterin order to realize the accurate 3rd-harmonic detection on a single-phase active filter. Measurement results of harmonic distortion of source voltage in a building is also shown in this paper. It is clarified in a simulation and experiment that the active filter can suppress the 3rd-harmonic voltage without increasing neutral conductor current.
A novel current source inverter system interconnected to the single-phase grid is proposed. It has the same construction as the conventional three-phase current source inverter that is interconnected to the single-phase three-wire distribution system. Though the proposed circuit has no output transformer, it can be equivalently performed as the single-phase double cascade inverter by diverting the pole transformer in the utility system. By controlling the appropriate scheme, the output currents can be obtained as the five-level waveforms and their distortions can be decreased sufficiently. It is applied to the interactive electric energy storage system with batteries and the basic discharging characteristics are discussed experimentally.
Recently, various types of vernier motor are developed. The VR type vernier motor is a kind of three-phase reluctance motor, and its stator has slots and distributed three-phase windings. The rotor is slotted iron core without windings. Relationship between S, R and P is S = R±2, where S and R are the numbers of stator and rotor slots per pair of poles, and the number of poles P is two. The rotor of the vernier motor moves at a sub-multiple of the angular velocity of the stator mmf. The multiplying factor is P/R. Authors had reported that the VR type vernier motors are analyzed as a three-phase reluctance motor, and have obtained the voltage equations on the γ-δ axis and expression of the torque.However, the asynchronous characteristics of the vernier motor are not clear yet. In this paper, the asynchronous characteristics of the vernier motors are analyzed with the symmetric components transformation and the commutator transformation. The voltage equations on the symmetrical co-ordinates and asynchronous and synchronous torque expression at steady state condition are obtained. The tests were performed on the trial motor. The calculated asynchronous torque has agreed well with the measured values.
We have presented a powerful scheme of investigating hybrid stepping motor characteristics by using 3D finite element method. A linear magnetic field analysis is effectively applicable to predict relative performance of several motors in an extremely short computing time. The waveforms of cogging torque by linear and nonlinear analysis resemble each other, while the wave amplitude in the linear analysis is about 2 times larger than one in the nonlinear analysis in the presented example. The overestimation factor of cogging torque is approximately constant for the same material composition.
This paper describes the effect of rotor-bar configuration on the starting and load performance characteristics of the self-starting permanent magnet synchronous motor. It becomes clear by using the time-stepped finite element technique that the rotor-bar configuration mainly affects the starting characteristics.
A novel high-frequency inverter circuit suitable for high-frequency current output utilizing distributed constant lines is presented. By taking the reflection phenomenon on the distributed constant line into account, conversion action from voltage to current, or vice versa, of the inverter can be explained. Hence, the proposed inverter generates a stable high-frequency current regardless of the output impedance of the load circuit. Its performance is verified through the 100-W 1-MHz inverter setup.