Research And Manufacture Of Un-touched Dynamic Loading System Under Centrifuge Overweight Condition Based On Wave Simulation

Caisson-Cylindrical Foundation Structures is a new structure which is applicable to deep water and soft foundation. In order to explore the representative behaviour and cognition that Caisson-Cylindrical Foundation Structures endured with horizontal force and periodic horizontal dynamic load, adopting the method of the Geotechnical Centrifuge Model Test, that is, simulating the horizontal force load and periodic horizontal dynamic load under the 105g supergravity circumgyrated by centrifugal machine.Under the 105g supergravity circumgyrated by centrifugal machine, it is not easy to bring to bear the horizontal dynamic load. The common loading system, such as Electro-hydraulic servo loading system, electromotor cam mechanism loading system etc, is out of reach preconcerted indices. So it is better to use the technique of un-touched electromagnetic Dynamic Loading System.This dissertation focuses on the hardwares of the electromagnetic loading system. mainly including electromagnetism and power amplifier analysis and design.The characteristic of this loading system is: large electromagnetic force, large air gap in magnetic circuit, large electrical current in coil, smaller installation size, low frequency Closeing to DC. hereby, must consider comprehensively the characteristics of DC and AC electromagnetism when designing. Given full consideration to both the magnetic circuit characteristics and time response characteristics. For one thing, selected ferromagnetic materials for core and armature in accordance with the characteristics of the work of electromagnet. And it is important to figure out the structure factor according to relationship between electromagnetic force and magnetic gap to design the type of electromagnet ofΠstructure. Then with the analytical methods, according to the Maxwell equation of engineering, we can calculate the relationship with magnetic induction, electromagnetic force and coil magnetometive force (ampere-turn). Next, according to the calculation results, we can make initial design of electromagnetism ,involving the core and armature's size, coil ampere-turn and wire diameter etc. After the initial design, we can check computations of initial data. Analyse the magnetic circuit According to the coil ampere-turn and air gap, it is easy to determine the characteristics of magnetic force with the anticipation force. Lastly, we should calculate coil ampere density and working temperature, so as to ensure the normal hours when coil working. After it is designed, it will proceed processing. Upon completion of processing, an experiment perform experiment on the actual electromagnetism will be conducted . The experimental results are basically the same design specifications. After the completion of electromagnetism design and process, it will determine the inductance and resistance by measurement, and analyse the coil drive current. The data are the next design requirements - power amplifier.Power amplifier (PA) is designed to drive coil to work. Power amplifier must be enough current output capacity. The design requirements is, 30A maximum output current (one-way),and 1? or so large output DC resistance, that is mainly expressed in inductive load. For this current level, high power silicon switches, such as GTO,IGBT etc, is more and more used for power drives now in the world. However, its turn-on/off time for controling of the electromagnetic coil can not be predicted. So the structure of power amplifier using the traditional one - traditional bipolar transistor power amplifier circuit. Through multi-stage amplification transistor constitute a form of class-b. Due to the larger current, Power transistor at the end of class is very important to use, so Pcm, Icm and Vbeo carried out a detailed analysis to select the power BJT - BUS14A. There are two type of connection about the BJT BUS14A at the end of class: Common Collector Circuit and Common Emitter Circuit. These two type of circuit were analyzed to determine a suitable circuit in the PA. The power capacity of BJT Products, that currently used for high-power application-level, is less than 250W, This is far enough to the PA (one-way about 1800W). So multiple paralle of high-power BJT way is used to improve the output capacity. Therefor it is described that current is impelled and distributed. Heat transfer is another key issue for high-power BJT. When temperature on high-power BJT maintain below a certain temperature (Tc), PA can be guaranteed the normal operation. so the problem of heat transfer is analyzed and researched in order to sign the structure with excellent cooling capacity. Since the PA driving a smaller DC resistance load, of which inductance is larger. When di/dt changes in current, there will be high enough electromotive force.It would be absolutely fatal to the high-power BJT. Therefore this problem is analyzed and researched to design suitable protection circuit to restrain the anti-electromotive force, and restrict on max current in high-power BJT. Ensure the high-power BJT for working safely in connection,disconnection or performance status. This section circuit is also connected to power supply, automatic temperature control circuit, to design of a set of logic, circuit protection and control functions. The power amplifier supply voltage use two part of DC voltage : power output supply useing DC60V30A simulation, the part of pre-amplification,protection and logic circuit using low voltage DC12V, the 60V power voltage is only connected just before working, and, disconnected through urgent stop switch, to ensure the safety of equipment. After above parts of the circuit design and manufacture, adjust all the circuit to determine the optimal DC operating point. Because of vast difference in the larger environment and the work environment in our country, there are certain requirements for the appropriate operating temperature and environment, to ensure the normal operation of the entire system. After completed, the PA was tested and applied in Changchun and Nanjing. The PA is meet the design requirements.After the whole system is completed, model test was carried out on the ground and geotechnical centrifuge testing machine with satisfactory results.