1 Introduction
Due to its simple structure and high power density, permanent magnet generators are widely used in aviation equipment. However, with the requirement of aeronautical engine airborne full authority digital electronic control system against short circuit, wide speed and high reliability generator power system, Generators with dual or multiple winding redundancy and long-term short-circuit operation are inevitably a top priority.
Although some current generators have two sets of windings, which also allow short-time short-circuit conditions, they cannot achieve true redundancy, that is, when one winding has a short circuit or an equal failure, it directly affects the other winding. Working performance; even if one of the windings can withstand short-time short circuit, its short-circuit current is very large, it will reach several dozen times, several hundred times or even thousands of times of the rated current, and the high heat generated will directly affect the other winding damage. . Conventionally designed generators are generally difficult to withstand high temperature working environments close to 200 ° C. High temperature, short circuit conditions even cause irreversible demagnetization of rotor permanent magnets, which brings devastating disaster to the CNC system and seriously affects the reliability of the engine system.
In this paper, the design scheme of a new type of short-circuit-resistant generator is given from the aspects of rotor structure and stator winding form. The simulation results of Ansoft simulation and comparison show that the design scheme is feasible, and the developed generator has good short-circuit resistance. High temperature resistance, wide speed resistance and true redundancy.
2. Design of anti-short circuit generator
2.1 System requirements for generators
The engine numerical control system requires the generator wide resistance range of 2000r/min~25000r/min, the voltage regulation in the full speed range is 28.5V±0.5VDC, and the 160°C high temperature working environment (short time 180°C), long-term short-circuit resistance In this case, the ultimate power demand in the full speed range is not less than 250W, and the limit power demand in the range of 3000r/min~25000r/min is not less than 280W. Any one-phase condition at 45% speed does not affect the normal operation of the other channel. Dual channels allow for long periods of short circuit without affecting other accessory equipment in the system.
The system requires generator weight ≤ 3.5kg, shape φ113mm & TImes; 125mm (excluding the outer circumference of the mounting flange), good air tightness, interchangeability, maintainability, reliability, safety, environmental adaptability, meet airworthiness requirements Wait.
2.2 Design ideas
Combined with the requirements of various performance indicators of the generator, the designed generator should meet the requirements of wide speed, high speed and high power density. The permanent magnet rotor becomes the preferred design scheme; it must meet the redundancy of the single channel phase loss fault. The residual function, the conventional winding design idea is not feasible, and a new anti-short-circuit winding scheme must be adopted.
According to the requirements of wide speed and short-circuit resistance, the design of the rotor selects the tangential magnetic circuit structure and multi-pair type; the stator design focuses on the design of the new winding, and theoretically increases the winding turns of the generator to reduce the generator. The short-circuit current multiple, but the actual design is not feasible due to the limitations of the shape structure, output demand, etc. In the design, the total number of turns is kept constant, and the scheme of reducing the number of coils and increasing the number of turns of a single coil to increase the leakage reactance is adopted. To improve the generator short-circuit current, the independent winding design type is used to realize the true redundancy function of the channel.
2.3 Simulation Analysis
The simulation model of the generator is established according to the design idea, and the simulation optimization design is carried out by Ansoft. The internal magnetic density characteristics of the generator are shown in Fig. 1. The magnetic point at the top of the intersection of the magnetic steel and the yoke is high, and the other rotor and stator parts are The magnetic density is lower than 1.3T.
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