A novel linear induction motor for electromagnetic aircraft launch system
A variable pole pitch linear induction motor (VPPLIM) is proposed as a new member of the family of electromagnetic aircraft launch system (EMALS). With proper designing of the variation of the pole pitch, the VPPLIM could accelerate the aircraft almost uniformly at the condition of usual AC supply, avoiding use of large scale power electronics converters. The special considerations in the design of VPPLIM, such as the structure topology and the variation of the pole pitch are discussed detailedly in the paper. The acceleration performance of the VPPLIM fed by a constant voltage constant frequency supply is analyzed by means of the quasi-steady-state 2D magnetic field model and the difference model of mover's dynamics. A two stage method is proposed to simulate the acceleration performance of the VPPLIM based on a 2D thrust table of the motor achieved by finite element method (FEM). The calculated features of the prototype VPPLIM consist well with those expected for EMALS.
A Maximum Constant Boost Quasi Z Source Invertor with Third Harmonic Injection for Linear Induction Motors
- Three phase voltage linear induction motors (LIMs) are emerging as a reliable means of providing both fast transport solutions and significant amount of linear thrust. However, conventional Voltage Source Invertor (VSI) and Current Source Invertor (CSI) motor drives applied to LIMs suffer from the generation of harmonic currents from the nonlinear nature of the LIM. This paper presents an improved Quasi-Z-Source Inverter (QZSI) for a linear induction motor (LIM) whose controller has been built, and its simulated results. The proposed QZSI controller herein for a LIM will injects uniformly spaced shoot through states, and promises a high output voltage gain and reduced THD.
Prophets praying for, or preying on people’s faith: A reflection on prophetic ministry in the South African context
In mainline churches, the ministry of prophecy or the prophetic ministry involves the proclamation of the gospel. This, in turn, is related to the every-believer ministry. However, there is now a resurgence of the prophetic ministry as a special office as evidenced by the establishment of neo-prophetic churches. This article argues that neo-prophetic churches are tapping into people’s longing for the fresh divine word to speak directly into their personal situations. The article also probes whether neo-prophets in the prophetic activities are not also preying on people’s faith.