Magnetic field dependence of shielding current density in Y-Ba-Cu-O rings at 77 K

A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ _cs and the intergranular transport current densityJ _cr are identical if the measurement conditions are similar. A degradation ofJ _cs measured in the external field with AC ripple has been observed.     

A new three-phase power-factor correction (PFC) scheme using twosingle-phase PFC modules

In this paper, a new three-phase power-factor correction (PFC) scheme is proposed using two single-phase PFC modules. In this approach, the "three" phase input is first transformed to "two" phase by means of a 0.14-pu-rated autotransformer. Two standard single-phase PFC modules are then employed to process the "two" phase power to DC output. Split inductors and diodes are employed to limit interaction between the two PFC stages. Due to cascade operation of two PFC stages, low-frequency (120 Hz) ripple in the DC-link capacitor is cancelled. Detailed analysis and simulation results are presented. A 220-V 1.5-kVA design example along with experimental results is shown     

Analysis and design of electronic transformers for electric powerdistribution system

A transformer performs many functions such as voltage transformation, isolation and noise decoupling, and it is an indispensable component in electric power distribution systems. However, at low frequencies (60/50 Hz), it is a bulky and expensive component. In this paper, the concept of electronic transformers is further extended and explored for its suitability in power distribution systems. It should be noted that from the input/output behavior, the electronic transformer and the conventional transformer are identical. Possible topologies employing static converters connected on the primary and secondary sides are explored to realize high-frequency operation of the magnetic core. To assist the commutation process, a four-step switching has been developed which does not require the use of snubbers. Reduced size, losses, higher efficiency, and better voltage regulation are some of the advantages of this approach. A 10 kVA design example along with experiment results are discussed. It is shown that a transformer designed with a conventional grain-oriented silicon-steel core can process three times the power at 1 kHz operating frequency as compared to 60 Hz. The proposed method is scalable in voltage/current with the currently available insulated gate bipolar transistor (IGBT) devices connected in series without special snubbers     

Integrated reactive components in power electronic circuits

Methods of integrating capacitive and inductive components into new compact devices are presented. Configurations for integrating various combinations of L-C networks are shown. A example of the construction of an integrated L-C for a series-resonant converter is evaluated both practically and experimentally     

A new active interphase reactor for 12-pulse rectifiers providesclean power utility interface

In this paper, a new active interphase reactor for twelve-pulse diode rectifiers is proposed. The proposed system draws near sinusoidal currents from the utility. In this scheme, a low kVA [0.02 P_o (PU)] active current source injects a triangular current into an interphase reactor of a twelve-pulse diode rectifier. This modification results in near sinusoidal utility line currents with less than 1% THD. It is further shown that a low kVA, 12-pulse system with an autotransformer arrangement [kVA rating of 0.18 P_o (PU)] can be implemented with the proposed active interphase reactor. The resulting system draws clean power from the utility and is suitable for powering larger kVA AC motor drive systems. Detailed analysis of the proposed scheme along with design equations is illustrated. Simulation results verify the concept. Experimental results are provided from a 208 V, 10 kVA rectifier system     

Characterization of Programmed-Waveform Pulsewidth Modulation

Programmed-waveform pulsewidth modulated (PWM) waveforms, applicable to ac-dc/dc-ac converters, are synthesized and analyzed in terms of several structural parameters. By invoking sensitivity studies and heuristics, optimal PWM structures are identified and contrasted. The results show total harmonic performance as a function of switching levels, waveform types, commutations per cycle, and filter bandpass.     

Computer-aided design and application of integrated LC filters

In this paper, methods of design and application of an integrated inductor-capacitor-transformer (LCT) are presented. A generalized modeling approach is also described. On the basis of this model and by using practical data, CAD software is developed for LCT, Several integrated LC and LCT samples were designed, built, and tested. Finally, a resonant power converter, using the integrated LCT, was built and tested     

Experimental assessment of wavelength margin in 20 Gbit/s WDMsoliton system over 18 Mm distance

The authors show that the operating wavelength range of a 10 Gbit/s single-channel soliton system using sliding-frequency guiding filters over a 18 Mm distance reduces from 1.3 to 0.2 nm when the system is upgraded to 20 Gbit/s with a second wavelength channel. A record WDM propagation distance >19 Mm is obtained by tuning the channels in the centre of the operating wavelength range. This result is achieved without the use of dispersion management