How to find the matching ultrasonic transducer?

Date:Jan 18, 2021

How to find the matching ultrasonic transducer?

Let the transducer, the driving power supply, and the welding mold cooperate well to form a complete ultrasonic equipment can be referred to as matching for short. Since the impact of matching on the performance of the whole machine is decisive, the importance of matching cannot be overemphasized. The main consideration for matching is the capacitance of the transducer, followed by the frequency of the transducer.

It should be emphasized that the ultrasonic transducer itself is not an energy generator, it is just an energy converter. It converts electrical energy into sound energy (mechanical energy). Under the premise that the input (drive power) and output (horn, mold) are well matched, it can convert (output) a large amount of energy.

Input matching refers to the matching of the transducer and the driving power supply. If the output matching is good but the input matching is not good, the transducer is weak and the welding is not strong. If the output matching is not good but the input matching is good, the transducer will be overloaded, causing chip dislocation cracking, broken, broken screw, aluminum cracking or burning the power tube of the electric box. For example, if a car slams on the accelerator in neutral, the engine must be easily damaged.

The matching of the transducer and the driving power supply mainly has 4 aspects, namely impedance matching, frequency matching, power matching, and capacitive reactance matching. The most important ones are capacitive reactance and frequency. As mentioned earlier, because the ceramic sheet is an insulator, you can almost understand that the transducer is not energized, it is just equivalent to a capacitor. To make the transducer work, it is actually applied to it through the drive circuit high AC voltage, so that the capacitance of the transducer is charged and discharged. The piezoelectric ceramic sheet undergoes synchronous expansion and contraction under the action of an alternating electric field, forming the longitudinal vibration of the entire transducer, thereby driving the vibration of the horn and the mold. Therefore, if the capacitor matching is not good, the lighter is the weak transducer and the welding is not firm; the heavy one, the transducer heats up seriously, burning the electrodes and the high-power tube of the power supply. Our transducer products are accompanied by a product performance parameter table, which shows the capacitance and frequency of each transducer. The driving power supply should adjust the parameters of the high voltage transformer, matching capacitor plate, peaking coil, and frequency modulation coil according to the capacitance of the transducer. Due to the sensitivity of inductance and capacitance, power amplifier boards, choke coils and other peripheral circuits also affect the matching. And as the work progresses, the temperature of the transducer will rise, resulting in an increase in capacitance and the change may exceed 50%. If the capacitance cannot be matched effectively, the current and voltage phase difference in the loop will be very large. , The power factor is very low and the virtual work is high. Look at the high current, but the transducer is weak, easy to heat, and the power device of the power supply is also easy to heat and damage. Generally, the transducer electrode (ear) cracks or burns out, which is probably caused by this.

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