Magnetic circuit

About: Magnetic circuit is a research topic. Over the lifetime, 15707 publications have been published within this topic receiving 118099 citations.

Multi-range, high-speed A.C. over-current protection means including a static switch

Abstract: An electronic circuit breaker for use in A.C. power circuits is provided with means for varying the overload current response level at which the circuit breaker removes power from the load. The load current is conducted through a primary winding of a transformer, and a circuit breaker switch is responsive to voltage across the secondary winding of the transformer exceeding a predetermined magnitude corresponding to the selected overload current level to remove power from the load. A lockout circuit prevents reapplication of power other than by a manual reset switch. The overload current response level corresponding to the predetermined magnitude of the voltage across the secondary winding is variably selected by varying the inductive coupling between the primary winding and the secondary winding. The primary winding is wound about one leg of a magnetic core and the secondary winding is wound about another leg of the magnetic core. In one embodiment, the inductive coupling is varied by altering a reluctance gap between the first and second legs of the core. In another embodiment, the inductive coupling is varied by changing the effective reluctance of a third leg of the core in parallel magnetic circuit with the first and second legs of the core. Both means for varying the gap and means for varying the effective reluctance of a third leg of the core may be combined to provide different ranges of selectibility. The overload current response level may also be adjusted by varying a reluctance gap in the first leg of the transformer core.

Magnetic force control based on the inverse magnetostrictive effect

Abstract: We describe a novel magnetic force control method. The method employs a mechanical stress applied to a magnetostrictive material to control the attractive force between fixed and movable members of a magnetic circuit that includes a permanent magnet. The method has the advantage over electromagnet control that a constant force can be maintained without energy consumption. We discuss the variation of the magnetic force with compression of several magnetostrictive materials. The experimental results agree with theoretical predictions of magnetic force based on analysis of an equivalent magnetic circuit and the piezomagnetic properties of the magnetostrictive materials.

Generalised transformer model based on the analysis of its magnetic core circuit

Abstract: In this paper a new transformer model, named ‘geometrical’, is developed, based on the circuit analysis of its magnetic core. The method is general and can be used for any type of multiphase multiwinding transformer. The model simulates the transformer as a set of coupled branches and can be incorporated into the widely known electromagnetic transients program (EMTP). A basic advantage of the model is that it can represent any asymmetry of the transformer magnetic circuit. As a study case, the model of an actual 280 MVA autotransformer is derived and used for the simulation of various steady state and transient conditions.

Magnetic equivalent circuit modeling of induction machines under stator and rotor fault conditions

Abstract: In this paper, stator and rotor failures in squirrel-cage induction machines are modeled using the magnetic equivalent circuit (MEC) approach. Failures associated with stator winding and rotor cage are considered. More specifically, stator inter-turn short circuit and broken rotor bar failures are modeled. When compared to conventional modeling techniques, the MEC modeling approach offers two main advantages: 1) relatively high speed of execution, and 2) high accuracy. The developed MEC model is validated here with respect to the experimental tests and time-stepping finite-element simulations for healthy and various faulty conditions.