| Abstract:Introducing ultrasonic field into aluminum alloy melt in its solidification process plays an important part in improving the properties of casting ingots. The ultrasonic power supply is the central part of ultra-sonic casting system and its working performance has a directly effect on the kinetic characteristics of ultrasonic vibration system and then influ-ences the effect of ultrasonic treatments on the melt. Based on the tech-nical characteristics of ultrasonic casting, this article designed a new gen-eration of digital ultrasonic power supply and constructed the overall de-sign scheme with the diode rectifier, chopper voltage regulation and sin-gle-phase bridge inverter frequeney modulation. The study mainly fo-cused on the resonant frequency tracking system including the control methods and configuation of hardware and software. At the same time, the impedance characteristics of the load of ultrasonic vibration system was investigated and the relevant matching circuit was designed. At last a simulation of the power supply system was made, testing of the ampli-tudes of ultrasonic vibration system and ultrasonic casting experiments were performed. The results showed that:1. The frequency tracking method using fuzzy control theory and Phase-locked loop circuits together can modulate the frequency in a wide range and lock the resonant frequency quickly and accurately in a narrow frequency range.2. The tuning inductance and high-frequency transformer which de-signed for the load of transducer have a good effect on the tuning match-ing and impedance matching of the ultrasonic transducer, thus improving the power output and working stability of the system.3. When the power supply was used in ultrasonic casting of aluminum alloy, it had a quick response, low frequency offset, a stable work per-formance, a high output power and showed the best effect on grain re-finement. The performance parameters of the power supply reached the expected design goals. |
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