Magnetic Potential Difference Research Articles

Synthesis of Consequent Pole Vernier Permanent Magnet Machine Based on Oscillating Magnetic Potential Difference Model

Synthesis of Consequent Pole Vernier Permanent Magnet Machine Based on Oscillating Magnetic Potential Difference Model

Adaptive control of an unsteady stress oscillation in a functionally graded multiferroic composite thin plate

An unsteady stress oscillation is known to be caused in a functionally graded material (FGM) thin plate by the action of impact loading. Since the stress then changes alternately and intensively from compression to tension as time advances, it may lead to serious damage to the FGM thin plate. Therefore, the development of an analytical model for control of the dynamic stress adapted to the action of impact loading is required. In this paper, adaptive control of an unsteady stress oscillation is investigated for a functionally graded multiferroic composite (FGMC) thin plate subjected to uniform impact pressure. Material properties of the FGMC thin plate are assumed to vary in the thickness direction according to a power law distribution. This elastodynamic problem is analyzed under the assumption that the volume fraction exponent and uniform impact pressure are unknown, whereas a piezoelectric voltage is measured across the thin plate during the first cycle of the oscillation. The magnitudes of the unknown exponent and pressure as well as an appropriate magnetic potential difference for control of the unsteady stress oscillation are considered to be determined within the period of the second cycle from knowledge on the basis of the measured piezoelectric voltage. Finally, numerical calculations have been carried out for the case where the appropriate magnetic potential difference is applied to the FGMC thin plate from the third cycle. Obtained results demonstrate that the maximum amplitude of the controlled unsteady stress oscillation is successfully reduced by about 46% and the performance of the adaptive control is monitored through the piezoelectric sensing. In consequence, the analytical model for adaptive control and monitoring of the unsteady stress oscillation has been proposed.

Bending and free vibration of a circular magnetoelectroelastic plate with surface effects

Surface effects play a significant role in affecting the mechanical behavior of nanosized NEMS such as sensor, actuator, transducer. This paper studies the bending and free vibration of a magnetoelectroelastic plate with surface effects. By incorporating surface effects into the Kirchhoff theory of thin plates, the governing differential equation for bending and vibration of a magnetoelectroelastic plate is derived. Simply supported and clamped circular plates are analyzed for applied mechanical loading, electric voltage, and magnetic potential difference. An analytical method is presented to obtain closed form solutions for static deflection of bending and natural frequencies of free vibration. The well-known results of circular thin plates are recovered if ignoring the surface effects along with coupling coefficients. A comparison of the deflections and the natural frequencies with their counterparts in the absence of surface effects shows that surface residual tension plays a crucial role, which decreases the deflection and increases the natural frequencies. The influence of surface magnetoelectroelasticity is discussed and the small scale effect can be captured. The obtained results are helpful for design and application of NEMS.

FORCE OPTIMIZATION IN DC ACTUATORS

The use of electrohydraulic systems is becoming more widespread in industry. The control valve forms a vital component of any such system as it performs both power conversion and amplification. The valve is operated by a solenoid mounted on the end of the valve block. A typical solenoid actuator is shown in Fig. 1. Current through the coil generates a magnetic potential difference across the air‐gap, producing an attractive force between the opposing pole face and armature. The armature moves to close the air‐gap and minimize the reluctance of the magnetic circuit.

Die grundgleichungen des wanderfeld-MHD wandlers mit berücksichtigung der eisensättigung

In this report it is shown that it is possible to take the magnetic potential difference within the iron into account by generalized boundary conditions. Thus, the calculation does not require the addition of a further field section for the iron; the number of integration constants is not increased. The iron saturation needs to be taken into account because for the operation of a self-excited MHD generator it is necessary to have a curved voltage-current characteristic. Furthermore, greater channel heights require establishing certain ranges of saturation within the iron, in order to get the desired curved voltage-current line. With small channel heights the problem of saturation might exist in avoiding saturation in certain parts of the magnetic circuit. In both cases the equations mentioned in this report are applicable. Moreover, preparations were made to describe the electrical working conditions of the MHD generator. By limiting operation to small slips and by implying saturation it is possible to define impedances, which, in principle, shows that the working condition of an MHD generator has some analogy to that of the conventional induction generator. A corresponding equivalent circuit could also be developed. The power and the losses are calculated according to the instructions in [1].

Circuits Employing Toroidal Magnetic Cores as Analogs of Multipath Cores

Circuits which are analogous to multipath magnetic cores are described. Toroidal cores are employed to simulate the branches of the multipath core. The conservation of flux at a node is simulated by means of shorted windings connecting groups of cores. These insure that the sum of the flux changes in the cores on a given winding will vanish. Ampere's law is simulated by proper choice of both number of turns and core dimensions. Equations are derived which determine the parameters of the analog in terms of those of the multipath core. These state that the volume of a core must be proportional to the volume of the corresponding branch, that the number of turns a shorted winding makes on a core should be proportional to the ratio of core diameter to branch length, and that the number of ampere-turns of externally supplied drive should also be proportional to this ratio. Analog circuits employing single-turn coupling loops and cores of different diameters are discussed as a special case. Another special case employs multiturn windings but identical cores. It is shown that the current flowing in a shorted winding is proportional to the magnetic potential of the corresponding node of the multipath core. The use of the core analog for the direct observation of internodal magnetic potential differences is illustrated by means of oscilloscope photographs of the magnetic potential difference between the nodes of a three-rung laddic.

A magnetic bridge for testing straight specimens and an analysis of the hysteresis loop of cobalt-chrome steel

The author employs a permeameter resembling that of Iliovici, in which the currents in two coils providing the M.M.F. of a magnetic circuit containing the specimen are adjusted until no magnetic potential difference exists between a selected pair of fixed points on the specimen. In the present apparatus the required absence of magnetic potential difference is tested by bringing up a yoke till its ends abut upon the two points in question: the approach of the yoke should excite no current in a search coil wound on the specimen and connected in a low-resistance galvanometer circuit. Resistance is then added to the galvanometer, and the deflection caused by a reversal of the two magnetizing currents enables the flux density to be calculated. The hysteresis loss per c.c. per cycle in cobalt-chrome steel is found by this method to be approximately 0.056 Bmax1.7. ergs, though the index of Bmax. actually decreases with increasing values of the flux density. The magnetization curve for this substance, above the point of inflexion near the origin, is found to be given by H - c/β=d+H/βs, where β=B - H, βs is the saturation value of β, and c, d are constants. To form a permanent magnet whose external energy per c.c. is within 5 per cent. of the maximum obtainable, a magnetizing force of upwards of 1,000 C.G.S. units must be applied to cobalt-chrome steel. The βH loop between the +β and - H axes is given by a formula similar to that for the magnetization curve, with different constants instead of c, d, βs, the value corresponding to βs being much less than the true saturation density.