Search

The Electromagnetic Damping Generator (EDG) used for petroleum exploration is faced with the problem of high local temperature during its downhole work. To avoid the damage to its internal circuit caused by high temperature, the key EDG circuit is required to be heat-resistant based on the electromagnetic induction principle and the current heating effect. First of all, the working condition with the maximum heating power was figured out after studying the heating power characteristics of EDG. Then the multi-field coupling model of the temperature field, electromagnetic field and structure of the damper, as well as its iterative analytic model were established to identify the relationship between the temperature rise of the key location of the damper part and its working time in the downhole environment and the room-temperature experimental environment, which provided data support for EDG optimization design. Finally, a EDG prototype was developed, and the test bench was set up by replacing the load with resistors to verify the accuracy of the iterative analytical model. The results showed that the temperature value calculated by the model well fit the experimental value. Therefore, the downhole operation reliability of the EDG and the safety of corresponding bench tests are guaranteed, which has certain guiding significance for EDG optimization design and its experimental study. [ABSTRACT FROM AUTHOR]

In this article, a clear and concise analytical method for predicting the performance of a Liquid-cooling eddy current brake (LC-ECB) is proposed. The LC-ECB has a coolant channel in the rotor to allow direct cooling of the inner surface of the stator. The static air-gap magnetic field distribution is obtained by the dynamic magnetic equivalent circuit (MEC) method, and the magnetic flux leakage and global magnetic saturation effects are fully considered. The magnetic field intensity distribution function of the eddy current reaction magnetic field is derived for the first time based on Ampere circuital theorem. Considering the local magnetic saturation and skin effect, a novel double-iteration algorithm based on the conservation principle of magnetic pressure drop is applied to obtain the transient air-gap flux density distribution, and then the brake torque expression is obtained. The finite element method (FEM) and experimental results show that the proposed method is feasible and effective. The new model is easy to program and can be easily used in the initial design and optimization of LC-ECB. [ABSTRACT FROM AUTHOR]

This paper proposes an electromagnetic damping generator (EDG), which is a novel downhole generator for the rotary steerable system (RSS). The EDG is designed to solve the problem of unstable voltage output by the RSS generator. The generator is designed by integrating a traditional generator and an eddy current retarder (ECR). The system converts the excess kinetic energy of the EDG rotor into heating energy by the principle of eddy-current braking and resistance heating. The electromagnetic finite element models of the generator part and ECR part are established and solved by computer. The voltage and torque generated by the generator part and the braking torque of the ECR part are predicted. In the bench test, When the input power is 2537 W < Pinput < 3304 W, the EDG is able to output 300.8 V. When the input power is 3304 W, the output voltage of the ordinary generator is 346 V. The EDG can be adjusted by a decrement of up to 45.2 V to output the rated voltage. The problem of generator output voltage instability in the RSS is solved when mud flow is unstable. [ABSTRACT FROM AUTHOR]

We propose a novel dual air-gaps and liquid-cooled eddy current retarder (ECR) based upon observing the (1) heat fade of the continuous braking and (2) large rotor weight of the traditional ECR for heavy vehicles. The new ECR maintains a low working temperature because of the liquid cooling stator structure. The eddy current distribution and braking torque characteristic curves are obtained by finite element method (FEM). Combining with 3-D FEM, Kriging approximation model is employed to optimize the structural parameters of rotor tooth. Based on the optimization method, the number of rotor teeth is determined to be 12. The braking torque increases by 14.8% after optimization and the rotor tooth weight decreases by 9.5%, which reduces the adverse influence on the vehicle transmission system. The bench test was carried out to verify the optimized calculation results and the braking torque can be stepless controlled by adjusting the excitation current. Compared with traditional ECR, the dual air-gaps and liquid-cooled ECR has better continuous braking performance and is more suitable for heavy vehicle auxiliary braking. [ABSTRACT FROM AUTHOR]

In this paper, an electromagnetically actuated tube type micropump is proposed, conceptually designed and experimentally investigated. The micropump mainly consists of two electromagnets, a NdFeB permanent magnet, a ball-valve and a Teflon tube. The reciprocating movement of the permanent magnet is realized when the two electromagnets excitated alternatively. The liquid in the tube flows from the inlet to the outlet while the permanent magnet reciprocating in the tube regulated by a one-way valve. Maximal flow rate of 208.75 µL/min and maximum backpressures of 539 Pa were achieved at a applied current of 0.5 A when the actuation frequency is 5 Hz. Compared to other micropumps with membrane structure driven by an external electromagnetic actuator, the tube type micropump is more reliable, small in volume, easy to be fabricated and has zero dead volume and less turns of coil. [ABSTRACT FROM AUTHOR]