Magnetic Circuit Length Research Articles

Magnetic measurement of nanocrystalline alloy based on a single sheet tester

Generally, for the measurement of magnetic characteristics of nanocrystalline alloy, the magnetic circuit length (lm) is assumed as a constant, and magnetic measurement under square waveform is rarely focused. This paper examines that magnetic characteristics of nanocrystalline alloy are measured under sinusoidal waveforms and square waveforms based on a single sheet tester. The factors related to lm are analysed from the tested data under sinusoidal excitations, and a novel method to determine lm is presented, which is then extended to the case under square waveforms. By combining with a power electronic inverter, the influence of power electronic topology on measurements is analysed, and the oscillation mechanism of excitation current of single sheet tester is revealed. As a result, the limitation of the H-coil method for acquiring the magnetic field intensity H under square waveforms is pointed out, and improved magnetic circuit method is introduced. It is shown from experimental results that the proposed measurement system is useful for acquiring magnetisation characteristics of the nanocrystalline alloy.

Simulation of the Magnetic Field Distribution and Voltage Error Characteristics of the Three-Phase Three-Component Combined Transformer With New Three-Cylinder Core Structure

The disadvantages of the traditional three-column core structure three-phase three-component (TPTC) transformer are its incomplete symmetry, the different magnetic circuit length, and the coupling parameters, which lead to each phase voltage error varying differently. In this article, a new structure optimization design of a new type of three-phase three-element combined transformer with a new three-cylinder core structure was proposed. The simulation analysis of the magnetic field distribution and the voltage error characteristics of the voltage transformer with the new three-cylinder core structure was carried out. Compared with the traditional three-column core structure TPTC transformer, the magnetic induction intensity distribution of the voltage transformer with the new three-cylinder core structure is more uniform. The simulation results of the voltage error characteristics under normal load condition also show that with the increase in voltage, the voltage error of the voltage transformer with the three-cylinder core structure changes gently, and the error difference between the three phases is smaller. The TPTC combined transformer with the new three-cylinder core structure has better error characteristics under normal load conditions.

Investigation of the influence of the length of the intermediate magnetic circuit on the characteristics of magnetic gripper for robotic complexes of the mining industry

The analysis of the existing systems of mechanical grippers of various operating principles and operating environments, in the design of which both soft and hard magnetic materials are executed. The characteristics of existing prototypes are shown and the results of our own research are presented.The article presents a study of the effect of the intermediate magnetic circuit length on the characteristics of magnetic gripper, the principle of which is based on the control of the field of a permanent magnet. The gripper based on this principle of action does not require constant energy expenditures to maintain both on and off states.The description of the magnetic gripper design and the design of the test bench is given, as well as the results of a series of experiments to determine the strength of the release of the gripper at different lengths of the magnetic circuit in the on and off states, followed by statistical processing of the data. The intervals of the ranges in which with a high degree of probability there will be a value of the gripping disengagement force for various lengths of the intermediate magnetic circuit are identified. The nature of the distribution of a random variable, which is the force of decoupling of the gripper, is determined. The dependences of the gripper decoupling force on the length of the intermediate magnetic circuit for each of the gripper states are constructed. It has been established that a decrease in the length of the intermediate magnetic circuit is the cause of a decrease in the gripping adhesion force. Plots of the dependence of the gripper decoupling force were constructed using the modes of the force values varieties to visually display the experimental results. The maximum adhesion force of magnetic pickup – 9.5 kg – was achieved with an intermediate magnetic core length of 50 mm, the minimum with a length of 25 mm – 5.6 kg.

Current and Voltage Distribution Analysis of Control Winding in a 35-kV HTS-CR Considering AC Losses

A 35-kV/100-A high-temperature superconducting controllable reactor (HTS-CR) is under development based on the principle of adjusting the main magnetic flux density and the length of magnetic circuit. The control winding of the HTS-CR is made up of double pancakes (DPCs) that are wound with HTS tapes. In order to increase the current margin of HTS winding, a four-tape bundle conductor is adopted in DPCs. Although tape transportation is utilized to balance the inductance, the current of each parallel conductor should be calculated to get the critical current. In particular, the ac losses caused by the high leakage of flux density on HTS tapes may aggravate imbalance of current and voltage distribution. This paper builds the equivalent circuit model of the parallel conductor and calculates the distribution characteristic of ac losses. Current redistribution has been analyzed by importing the equivalent resistance. Meanwhile, voltages of parallel inductance have been detected to acquire a more intuitive reference, which will provide a basis and support for quench detection and protection.

Compact Magnetic Lenses for HV Electron Microscopy

The number of ampere turns NI at a given Bsat is the major factor in determining the size of conventional magnetic lenses in HV microscopes. As a consequence of increased size of the winding and hence of the length of magnetic circuit, the iron cross section has to be made large. This leads to large overall dimensions, high power consumption and difficulties in cooling and handling.