Research on a permanent magnet passively compensated pulsed alternator with ultra low mutual inductance research on a permanent magnet passively compensated pulsed alternator with ultra low mutual inductance
In this investigation, a permanent magnet passively compensated pulsed alternator (PMPCPA) with ultra low mutual inductance has been designed to provide an electrical pulse with the large power for the load in the shorter period. The electric excitation is replaced by the permanent magnet excitation, the passively compensated mode is adopted, and two-phase symmetrical windings with an electric angle difference of 90 degrees are respectively placed in the stator slots with both deep and shallow specifications to reduce the mutual inductance between the windings. On the basis of design scheme, the inductance of armature winding of alternator is calculated. Both noumenon and short circuit discharge models for the PMPCPA are established to perform the simulation, and the mutual inductance of PMPCPA is measured. The simulated and experimental results show that the present alternator can meet the design requirements, and the effectiveness of method for reducing the mutual inductance is verified.
Investigation on the Current Pulse Formation of Compulsators
A compensated pulsed alternator is a special synchronous generator which is based on the law of electromagnetic induction and the law of flux compression. It is intentionally designed to maximize short circuit current output by minimizing internal impedance through the action of flux compression and air-core topology. It is an attractive compact high pulsed power supply which is composed of energy storage, energy conversion and pulse formation. In order to investigate the principle of compulsators and the pulse formatting current, the expression of pulsed current in three different compensation models is derived in detail, which is based on the simplified schematic and some assumptions. The main purpose of this paper is to analyze the factors which determined the pulsed power current waveforms. The selective passive compensated model is taken as an example for the analysis. The software MATLAB is used to calculate and draw the pulsed current waveform. Some typical pulsed current waveforms are obtained and then compared. The pulsed current waveform which is determined by many facts, such as the trigger angle, the relative position of winds, the coupling depth, the compensation model and so on, is analyzes. The waveform with and without compensation is also compared. Through the analysis of the pulse formatting current of compensated pulsed alternator, the relationship which is between the current pulse and the factors listed above is obtained. In the end, some conclusion is obtained by theory analysis,which is valuable for design of compensated pulsed alternators.
New Sweet-Tasting C21-Pregnane Glycosides from Pericarps of Myriopteron extensum.
Ten novel C21 pregnane glycosides, extensumside C-L (1-10), were isolated as highly sweet-tasting substances from the edible pericarps of Myriopteron extensum (Wight) K. Schum by sensory-guided fractionation and purification. Their structures were determined through 1D and 2D NMR, such as HSQC, HMBC, 1H-1H COSY, HSQC-TOCSY, and ROESY, as well as other spectroscopic analysis combined with chemical evidence. These compounds shared the same aglycone, 3β,16α-dihydroxy-pregn-5-en-20-one, and contained the deoxysugar chain and the glucose chain which were linked to C-3 and C-16 of the aglycone, respectively. The sweetness potency was evaluated by a human sensory panel test and preliminary structure-taste relationship was discussed. The sweetness intensities of these compounds are between 50 and 400 times greater than that of sucrose. Furthermore, quantitation analyses of compounds 1, 3, 4, and 6 in different parts of M. extensum indicated that the concentrations of these sweet components in the pericarps are obviously higher than those in stems and roots.