Squeeze damping of giant electrorheological fluid tuned by pulse width modulation

In this thesis, a boost chopper using PV (Photovoltaics) system and PWM (Pulse Width Modulation) voltage type power converter were constructed to provide a pleasant environment to the patients in the hospital wards by controlling temperature, humidity and air-conditioning & heating. For the stable modulation of solar cell, synchronizing signal and control signal were processed using one chip microprocessor. Power converter system was constructed with booster chopper and voltage source inverter and test was carried out for both devices. Constant voltage control method was used to track a maximum power point at boost converter control. For the inverter control, synchronizing signal and control signal were processed by microprocessor for the stable modulation according to the switching theory of SPWM (Sinusoidal Pulse Width Modulation) and directions to each sector. Test was carried out for inverter control using SPWM control method. In addition, grid voltage was detected and this grid voltage and inverter output were operated at the same phase for the phase locking with PWM voltage source inverter so that surplus power could be linked to grid. This characteristic was applied on the temperature and humidity sensors in the general buildings and buildings having specific purposes such as hospitals. The good dynamic characteristic of inverter could be obtained by these applications. Also, PWM voltage inverter maintains a high power factor and low-frequency harmonic output so that power can be supplied in the load as well as system.

This work proposes a methodology to estimate core losses under pulsewidth modulation (PWM) or dc bias ripple voltage excitations. A special hysteresisgraph was built to measure toroidal samples under pulsed voltages. An experimental methodology, based on the principles of ferromagnetism, was implemented to investigate minor loop losses in toroidal samples of oriented and nonoriented FeSi. Triangular induction waveforms with constant dB/dt were generated. The results demonstrated that minor loops produced by PWM voltage, do not affect the major hysteresis loop losses nor the losses of other minor loops measured at different points of the major loop. In these experiments, minor loop losses under PWM voltage were very similar to minor loop losses under dc bias ripple voltage. Aspects of the behavior of minor loop losses as a function of amplitude and magnetic flux density are reported in this work.

End turn grading with resistive–capacitive coupling experiences severe electrothermal stress when subjected to pulse width modulation (PWM) voltage. In this paper, several experiments and simulations were carried conducted for four types of end turn grading. First of all, the temperature rise in the end turn grading increased with a decrease in rise time. When the rise time was less than 500 ns, the temperature rise at the terminal was higher owing to the increased capacitive current coupled from the main wall insulation. Further, the current in the linear region exhibited minimal variation at different fundamental frequencies resulting in synchronized the temperature rise at the terminal and overlap. Furthermore, the jump voltage was the key factor influencing temperature rise in end turn grading, confirmed by comparing different voltage magnitudes. Finally, the transient behaviour of the maximum field in the stress grading material was determined at rise time. The experimental and simulation results indicate that balancing and interdependently addressing the electrical and thermal stress protection in end turn grading is crucial. The study aims to provide an experimental and theoretical foundation for an insulation system of inverter‐fed rotating machinery operating under PWM voltage.

The number of voltage levels available in pulsewidth modulation (PWM) voltage source inverters can be increased by using a split-wound coupled inductor within each inverter leg and interleaved PWM switching of the upper and lower switches. The magnetizing inductance of the symmetrical split-wound inductor filters the high-frequency PWM voltage differences between the upper and lower switches. The same inductor presents a three-level PWM voltage at the inverter output terminals, with the winding leakage inductance being located in series with the low-frequency output current. Deadtime PWM signal delays can be reduced as DC-rail short circuits are not possible: as a result, the quality and voltage range of the PWM output is improved. Since the inductor windings are technically exposed to high-frequency PWM AC voltages with no DC components, device voltage drops help to reduce the buildup of winding DC currents. Theoretical analysis and a sample design case are presented to illustrate how to design suitable inductors for the various topologies. Simulation and experimental results are used to illustrate the operation of the proposed inverter structures.

Saliency-based position sensorless drive with the pulse width modulation (PWM) voltage injection has advantages of high estimation bandwidth and low acoustic noise. However, multiple currents should be sampled every PWM cycle for spatial saliency calculation. Considering the standard SVPWM control, the PWM voltage injection distorts the symmetric voltage pattern with additional position estimation errors. This paper proposes a modified PWM through the measurement vector insertion (MVI) for PWM injection based position estimation. By integrating the MVI with discontinuous PWM (DPWM), the proposed PWM injection maintains the symmetric voltage pattern for FOC. This MVIPWM injection is compared to other PWM injection methods on an interior PM machine. All the advantages of MVIPWM on the saliency-based drive are verified by experimental results.

Recent developments in power electronic technologies lead to new challenges for insulation systems. This contribution aims to clarify the influence of a broad range of mixed-frequency (MF) medium-voltage and environmental stress parameters on the aging of epoxy insulation. For this purpose, test samples are stressed with an AC (50 Hz) or a DC voltage, superimposed with a pulse-width-modulated (PWM) voltage (kHz range). An analysis of the samples’ health state is carried out after the aging by the evaluation of potential aging markers (AC breakdown strength, dielectric permittivity, glass transition temperature, Fourier-transform infrared spectroscopy spectra). Although the main focus of this work is on aging below the inception of partial discharges (PDs), it was first confirmed that PD-related aging depends mainly on the peak voltage stress. In contrast, the results obtained by aging below PD inception suggests a dependence on the root-mean-square of the applied voltage stress, and consequently on the energy dissipation. Aging in the PD-free regime was only observed at alternating electric field stress and high relative humidity or elevated temperatures. No influences of space charge and of the slew rate of the PWM voltage were observed. Remarkably, higher PWM frequencies lead to less insulation aging. This might be attributed to the increasing hindrance of polymer side chain movement at higher frequencies, as observed by dielectric spectroscopy. In addition, it is indicated that the aging mechanisms under MF voltage stress result from superimposed single-frequency aging mechanisms and that aging is activated after a latency period. Of the investigated potential aging markers, only the residual breakdown strength revealed aging effects, which correlates with lifetime observations in the PD-free voltage stress regime. It is hypothesized that the aging mechanism is associated with a rearrangement of the free volume in the polymer, followed by a localized breaking of van der Waals bonds.

To improve the vibration isolation performance, a conventional passive two-parameter vibration isolator (VI) usually adopts the method of adding constant damping for energy dissipation. A compromise is made between the suppression of resonance peak and the rapid attenuation of transmissibility in the high-frequency band. A four-parameter-VI with frequency-dependent damping is a potential solution for this problem. The theoretical models of system transmissibility and equivalent damping are established by a normalization method, and the vibration isolation performance is compared with that of the two-parameter-VI and the three-parameter-VI. A novel four-parameter-VI with damping generated by a giant electrorheological fluid (GERF) damper is designed. The mechanical properties of the GERF damper are tested, and its damping effect is evaluated using an equivalent linearization method. Then, the vibration isolation performance of the four-parameter-VI is tested. The results show that: the vibration isolation performance of the four-parameter-VI can be affected by the damping ratio and the mass ratio. The four-parameter-VI exhibits the frequency-dependent damping characteristic of large damping in the low-frequency band and small damping in the high-frequency band by appropriately setting parameters. The vibration isolation ratio of the four-parameter-VI to white noise reaches 91.1% in the time domain with appropriate parameters, and the peak of the power spectral density curves decreases from 1.2 × 10−3 g2 Hz−1 to 0.16 × 10−3 g2 Hz−1 with a reduction of 1.04 × 10−3 g2 Hz−1 .

This paper presents a new approach for diagnosis of short circuit Insulated Gate Bipolar Transistor (IGBT) faults in a three-phase voltage-fed motor drive. The three-phase Pulsewidth Modulated (PWM) voltage signals are monitored and digitised into two discrete levels. The combination of discrete voltage levels of the three phases composes eight voltage states. For a healthy Sinusoidal PWM (SPWM) motor drive, all eight states are monitored within one carrier period. However, when a fault occurs certain states cannot be obtained. A fault signature set is defined for each switch fault. By comparing the monitored states with the fault signature sets, the faulty switch is detected and isolated. A PWM voltage source inverter that feeds a threephase Permanent Magnet Synchronous motor with IGBT switch faults is simulated and the fault diagnosis algorithm is applied. The results show that the faults can be diagnosed within tens of microseconds. The robustness of the proposed fault diagnosis and isolation (FDI) approach to the load changes is tested by connecting the motor to a variable mechanical torque.

Simulation study on the improvements of machining accuracy by using smart materials

Fuzzy PWM based on Genetic Algorithm for battery charging

The inverters and control methods are applied in more and more fields with power electronics development. The technology of current hysteretic band PWM is a kind of easy and reliable control method. But the harmonic distortion of load current is big amplitude around switching frequency side band. The paper introduce a Varied Hysteretic-band Current control technique(VHBCC), this method can spreads the spectrum contents of load current around switching frequency side band, reduces the harmonic distortion of load current . At last, The results of simulation prove the method feasible and effective.

Vibration and acoustic noise are two critical issues for switched reluctance machine (SRM). The abrupt change of phase current mainly contributes to high vibration and noise under conventional unipolar excitation, sinusoidal bipolar excitation considered in this paper can suppress the vibration in SRM. However, to realize the smooth sinusoidal bipolar excitation, different pulse-width modulation (PWM) strategies can be employed. In this paper vibration and acoustic noise of a prototype 6/4 SRM under different load and speed, which employs hysteresis current control (HCC) and space vector pulse-width modulation (SVPWM), is investigated, together with the conventional unipolar excitation, which is modulated by voltage PWM. It shows that the lowest vibration and acoustic noise are obtained if the SRM excited by the sinusoidal bipolar excitation modulated by the SVPWM, regardless the speed and load. However, the HCC technique exhibits the worst vibration and acoustic noise due to random switching frequencies and mechanical resonances, although less sensitive to the load and speed. In contrast, the acoustic noise with the conventional unipolar excitation is sensitive to both load and rotor speed, when the sinusoidal bipolar excitation modulated by SVPWM is employed it is sensitive to the speed but not to the load.

A novel dimmable light‐emitting diode (LED) driver is proposed in this study. The circuit topology uses two active switches. One active switch shared by a buck–boost converter and a buck converter is operated at high‐switching frequency while the other one is low‐frequency pulse‐width modulated to dim high‐power LEDs. The buck–boost converter plays the role of a power‐factor corrector. It operates at discontinuous‐conduction mode to waveshape the line current to be sinusoidal and in phase with the input‐line voltage. The buck converter regulates the dc‐link voltage to output a low‐frequency pulse‐width modulation (PWM) voltage to drive high‐brightness LEDs. Since only one power‐conversion process is required, and the buck converter works only when the low‐frequency PWM voltage is at a high level, the proposed LED driver has the advantage of high efficiency. Besides, it achieves unity power factor and low total current harmonic distortion.

The designed switch mode power supply source (SMPS) is described. It consists of a net filter, power factor correction (PFC) circuits, pulse width modulation (PWM) controller, driver stage, PWM output stage, output transformer and voltage converter. The PFC principle is described in detail. The PWM output part was designed to deliver output power of the SMPS up to 1200 W. The calculated and the measured parameters of the output pulse transformer and the filter inductor are given. The measured values of the designed SMPS show the efficiency nearly 90% at the half and the maximum output power value.

When calculating the permanent magnet (PM) eddy current loss (ECL) in the interior permanent magnet synchronous machine (IPMSM) under pulse width modulation (PWM) voltage source inverter (VSI) supply, it is very important to take the high frequency harmonic voltages (HFHVs) in the input voltage into consideration because most of the PM ECL in IPMSM with distributed windings is caused by them [1–2]. However, common finite element analysis (FEA) with sinusoidal current source supply isn’t able to take the HTHVs into consideration and the coupled field-circuit time-stepping FEA under PWM VSI supply with fine time step is needed for the calculation, which is very time-consuming especially when conducting 3D FEA to take the end effect and axial segmentation into consideration. A hybrid method with the combination of 2D FEA and analytical method has been proposed in [3] for fast calculating the PM ECL considering axial segmentation. However, the 2D time-stepping FEA with fine time step, which takes several hours for one case study, is still needed for the PM ECL calculation under one load condition with the method proposed in [3]. In this paper, the analytical method in [3] is further developed and applied for the PM ECL calculation of an IPMSM applied in the HEV application [4]. Rather than calculating the PM ECL with the average flux density passing through the PM as input [3], the relationship between arbitrary HFHV and the corresponding PM ECL is established. Hence, the total PM ECLs can be calculated with the FFT results of the input line-line voltage directly without time-stepping FEA at a given load condition.