A new tracking method with FPGA chip for ultrasonic welding system
A new feedback control method of using field-programmable gate array (FPGA) chip for ultrasound welding system is appeared in this article. This feedback control circuits of ultrasound welding system consists of microprocessor control unit, signal generator, power amplifier, the feedback of voltage detector and current detector, etc. The experimental results exhibited this feedback control method can effectively and automatically catch frequency and rack a proper frequency for the ultrasound welding system.
Frequency control of MOSFET full bridge power inverter for maximizing output power to megasonic transducer at 3 MHz
The frequency of the MOSFET DC-to-RF power inverter is precisely set at the series resonant frequency of a megasonic transducer by controlling the oscillation frequency of the PLL when the MOSFET DC-to-RF power inverter is used to drive the megasonic transducer having an impedance of as low as 5 to 6 ohms or less. The frequency control system features a current sensor having an effective internal impedance of as low as 0.25 ohm which is negligible compared with the impedance of the megasonic transducer at the series resonant frequency. The impedance of the inverter load composed of the output transducer, matching capacitor, coaxial cable, megasonic transducer, and current sensor is calculated to determine the frequency control range of the PLL. In accordance with the result of calculation, the performance of the phase-frequency comparator, low pass filter, and VCO is decided. When the RF output power of the MOSFET power inverter was 60 W with a power conversion efficiency of 95%, the frequency control range was 2.8 MHz to 3.2 MHz. The PLL covers the range of frequency shifts and variations in the megasonic transducer and VCO.
Numerical Simulation of Induction Heating Process of Continuous Casting Slab
Compared with traditional blazing furnace, the Continuous Casting-Direct Rolling is an advanced manufacturing steel technology, which can reduce energy waste, decrease pollution and enhance efficiency. The characteristics of steels during induction heating are complex, the change of material properties with temperature makes exact analysis methods very difficult to implement. Therefore, a powerful computer aided numerical tool (i.e., finite difference analysis) is selected to numerically model the induction heating process in this paper. The mathematic model coupling with electromagnetic field and thermal field was established, and it was solved by finite difference method (FDM), thus the slab temperature distribution and its variation with time were obtained, and the characteristics in whole induction heating process were studied. To validate the program feasible, the results were evaluated and compared with experiment results, which showed that the simulation results are reliable and effective. The skin effect in heating process from the two results was studied and demonstrated, the temperature change caused by different parameters such as the induced power intensity and the corner radian were also presented, which indicate that the slab temperature can be heated uniformly through adjusting these parameters, thus the continuous casting slab can meet the rolling requirement.