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# Pzt ultrasonic transdcuer power

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#### engineer1000

I am trying to find out what the difference is between a 50W, 60W and 100W pzt 40khz ultrasonic transducer. The ceramic seems to be the same size on all three, is it that the metal pillars are bigger and so the transducer can assorb more heat?

I have an impedance plot of a 50W 40KHZ transduc which gives a resistance of 1.8R when at approx 40khz. So for 50W I should olny need to put in a 28V SINE WAVE and get a current of 5A. This doesn't work.

your maths is wrong, 28/5 = 5.6 ohms NOT 1.8 ohms, also 28 X 5 = 140 NOT 50. If you fed the device with 28V at the spot on frequency and its 1.8 ohms the current should be 28/1.8 ~15 A, 28 V at 15 A = 420W.
So start again with some meaningful figures. Most transducers have a high capacitance reactance (small value of capacitor) in series with the resistive bit, which is the bit that actually dissipates the power. This means that you have to put in a series inductance that tunes out the capacitance at the working frequency. So re-check your figures.
Frank

Thanks Frank,
What I really want to know is how a manufacture classes an ultrasonic transducer as 50Watts or 60 Watts or 100Watts, are the ceramic rings the same? or are they subtly different?

I don't make piezeo units, but it could just be that a substandard 100 W unit when driven at this level goes into a different mode and its frequency changes... As it works at 60W, its labeled "60W". Or as you say different ceramic thickness/mounting/heatsinking.... Why don't you check and see if other parameters have changed, this would indicate some difference in type.
frank

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