We already described the nine-phase inverter driving system providing both the triple three-phase voltage source inverter with 180 degree conducting period and the AC motor windings with triple three-phase construction. The nine-phase inverter driving system used three small capacity threephase coupling reactors having special windings for current balance and reduction of higher harmonics. In addition, for voltage control, current balance, and waveform improvement, optimal PWM pulse patterns were applied to the six-phase inverter driving system using a three-phase coupling reactor to provide double three-phase construction. In the system based on the mode in the title, the PWM control was applied to the nine-phase inverter driving system described above. The coupling reactors in the system balance the fundamental currents of three sets of three-phase inverters and also absorb higher harmonic voltages other than 18p±1 (p=1, 2, …) orders. The optimal pulse patterns found by the approach to make the performance index minimum using the Lagrange's multiplier method can be applied to the PWM to reduce the higher harmonic currents greater than those calculated by the modulation method comparing sinusoidal signal wave with triangular carrier signal. This system can have a larger capacity than the six-phase PWM inverter driving system in which coupling reactors absorb higher harmonic voltages other than the 12p±1 orders and also improve output current waveforms. In addition, the system includes the capacity of coupling reactors a little lager than the six-phase PWM inverter driving system but enables operation with smaller torque ripples and electromagnetic noises in low to high frequency ranges.
Harmonic components included in the output waveforms of inverter circuits cause magnetic noise, that is, audio noise, from the output transformers or load motors. In order to estimate the magnetic noise due to the harmonic components, we have already proposed the equivalent noise voltage Es and current Is. In this paper, by applying the above Es, we compare quantitatively the magnetic noise in the various ordinary voltage source inverters, both PWM inverters with multi-pulse waveforms and PAM inverters with multi-step waveforms. Then, in order to reduce the magnetic noise, we improve the output waveforms of the PWM inverters by applying Es into the idea of harmonic elimination. Moreover, by employing PAM system as voltage regulation in the above method, we can get the more improved output waveforms with lower noise and also lower distortion.
The progress of microelectronics and microprocessors has advanced digitization of control circuits so that sensors have been expected to have digital output. Current sensors are basic in electrical drives, and the control accuracy depends on their performance. However, a current sensor using Hall-device has a non-linear error of 1%. In order to solve this problem, a Hall-effect current sensor, or a so-called closed loop current sensor, has been developed, which is combined with a current transformer. The current of a secondary winding is compensated by the Hall-device so that the magnetic field in the toroidal core is kept at zero. In this case, the non-linear error is eliminated. In this paper, a digital output current sensor of 12 bits is developed, which is a combination of a closed loop current sensor with a voltage comparator and a counter. As this circuit includes a nonlinear component such as the voltage comparator, the limit cycle caused by non-linearity is analyzed. It is described that the oscillation can be suppressed by linearization using a flush type A/D converter of 4 bits.
A single-ended resonant type high frequency inverter using a Static Induction Transistor (SIT) described in this paper can be performed as a zero current switching (ZCS) operation without DC reactor. The SIT high frequency inverter is a low-cost one which has no transformer and it would be developed for a high intensity ultrsonic power supply and DC-DC converter. The circuit operation region not only ZCS but also ZCS • ZVS (zero current switching and zero voltage switching) were elucidated in the normalized plane. The characteristics of the inverter including the power control by frequency regulation were discussed. Furthermore the switching characteristics in the transientstate were investigated. These characteristics were substantiated on the basis of the numerical analysis and experimental results.
An on-line FMS scheduling system, which takes in consideration the routing flexibility is proposed in this paper. The FMS is modeled utilizing a Timed Petri net representation. This representation provides real time information about the production evolvement and the status of each machine and equipment. With this information the proposed system starts to search for the scheduling of the next orders to be assigned. The search is performed by a beam search based on-line decision method. The developed algorithm, integrating the Timed Petri net representation to the beam search, is described. To test the developed system Just-in-Time production objective was established. The performance of the system is evaluated through exhaustive simulations. The achieved results are very promising, as the proposed system leads not only to a better achievement of the production objective, but also to smaller variance under different scheduling conditions, suggesting greater reliability.
Because of its complicated flux behavior, shape effect of a ferrite orthogonal core (FOC) has not been made clear satisfactorily. In this paper, a shape effect of flux control characteristic by flux components for an FOC is presented. The flux control characteristics of component method, ratio of virtual flux-path-length, sectional area of body, ratio of permeance and thickness of common part are examined. Performance evaluation of flux control is examined between flux control sensitivity and flux control. The results, which are given by evaluation amount of flux control sensitivity and flux control ratio, show that the most respectable FOC has no thickness in common part, small amount of body and leg sectional area ratio, and the monoblock construction between the primary and the secondary side.
This paper proposes a disturbance suppression control with preview action for brushless & coreless type linear DC motor. Brushless & coreless type linear DC motor is coggingless and has long life. It is suitable for high speed and precise positioning control. Parameter variation and load change are regarded as equivalent disturbance signal and the compensation action is applied by utilizing the estimated value of the equivalent disturbance inside the inner loop. Next, Optimal preview control system is synthesized including the disturbance suppression control system mentioned above. Disturbance suppression, improving of phase delay and lowering of input peak value are attained in this control system. These effects are confirmed by applying the linear DC motor.
Recently, the influence on power supply systems and electronic instruments of noise from semiconductor circuits such as thyristor control circuits has become an important problem. In 1976, Kusko et al. proposed the transfilter, which is used both as a transformer and a low-pass filter to eliminate this noise. They proposed a simple equivalent T-type filter circuit having fixed circuit constants and a circuit equation for the transfilter. Then they showed that the transfilter has excellent frequency-cutoff characteristics through the use of the transfer admittance calculated from this equivalent circuit. However, this transfilter is both a R-L-C-low-pass filter and a leakage transformer having series and parallel ferroresonant circuits. Therefore, if the magnetic flux density in the core exceeds the linear range of magnetizing characteristics and enters the saturation range, the output waveform becomes distorted due to the effect of ferroresonances. To obtain good filter characteristics, we must keep the ratio of input voltage and output voltage constant. Waveform distortion by the effect of ferroresonances must also be eliminated. For this transfilter, we have developed an equivalent circuit and characteristics analysis method which considers the effect of magnetic saturation. We have shown that the proposed method has high accuracy, and we have also determined the designing conditions for obtaining a good transfilter.
High precision and good command response are the most important requirements in performance of constant speed rotation control systems. It is the rotational speed fluctuations caused frequent by rotational angle dependent disturbances that have hindered all efforts to improve the precision of such systems. This paper proposes a new approach focusing on the fact that this kind of disturbance constitutes cyclic function of the rotational angle. The proposed design is set in the ‘angle domain’ instead of the ‘time domain’ so as to eliminate such disturbances completely without regard to the rotational speed. The results of the simulation reported in this paper will prove that the constant speed rotation control system designed according to the proposed approach removes all rotational speed fluctuations apart from speed setting changes.