[SOLVED] Inductor Design in Ultrasonic Cleaner

I already have designed an Ultrasonic Cleaner circuit with IR2110 High and Low side driver. While referring other circuits, I noticed a series inductor in the path of Ultrasonic transducer. Why is a series inductor required and how can I design that inductor. How many turns and which wire to use etc.

40KHz(Generated By a Microcontroller) is at which I am Operating.
EF19 Core and Bobbin is available in market here. Can I use EE19 for this inductor??

The inductor may act as a choke or ballast, reducing AC current through the transducer after it gets running.

Or it may filter out high frequency (RF) harmonics so they don't radiate into space or travel into the house wiring.

You won't know how to construct it until you know what is the proper henry value, amp capacity, frequency response, etc.

gladiss said:

I already have designed an Ultrasonic Cleaner circuit with IR2110 High and Low side driver. While referring other circuits, I noticed a series inductor in the path of Ultrasonic transducer. Why is a series inductor required and how can I design that inductor. How many turns and which wire to use etc. 40KHz(Generated By a Microcontroller) is at which I am Operating. EF19 Core and Bobbin is available in market here. Can I use EE19 for this inductor??

Click to expand...

The series inductors act like frequency filters ( As the one used in audio network) Calculated, wound and alligned with air gaps to give a particular value which will act as a filter when used with parellel or series of capacitors ( which you have not noticed). Winding purely depends on what value you need. Any other or similar Cores can be used provided the winding fit in and you can get the same value of the inductor as in the later.
Cheers

Thanks BradtheRad and Pranam77. I got the point
1. I have to know the value of the inductor
2. Any Core can be used, important is value should be correct.

May I know how can I find out which value is required.

Here is my circuit.
I just used an inductor from another board..
I got a pure sine wave across Point A and B and I am Getting a Square wave across B and C.
Does it make any sense...
Power rating of the Ultrasonic Crystal is 30W.

To determine the optimal inductance value, you would need to measure the piezo transducer's impedance root locus. As a first guess, a 40 kHz series resonant circuit with the statical (low frequency) capacitance of the piezo can be choosen.

The inductor core should have an air gap, to achieve stable inductance and avoid core saturation. Number of windings for a given inductance value can be precalculated from datasheet data, or better adjust according to an inductance measurement.

Sorry, I don't have experience with ultrasonic cleaners.

I looked at your circuit. I believe the inductor's purpose is to create a resonance with the capacitors, to send current back and forth through the crystal.

The frequency may be at the crystal's self-resonant frequency. On the other hand it may be an off-frequency with the intention of preventing the crystal from going into overly strong oscillations on its own.

Did you get the inductor out of another ultrasonic cleaner? It may be a suitable value as is.

If it's operating at 40kHz then that suggests using components which yield a time constant in the vicinity of 2.5 x 10^(-5). The coil value would likely be under 1 mH.

However this depends on whether the crystal is meant to be exposed to 230 V or higher. If the crystal can only endure low voltages, then the coil may serve to choke current. Then a larger henry value would be in order, maybe over 1 mH, to generate reactance (impedance). Of course this depends on what other effective impedances are present in other components.

I think the actions of the inductor are :- 1. At the resonant frequency of the transducer, it might act like a resistor, this is the mechanical energy being put into the fluid plus a capacitor in series. The inductor then tunes out this capacitance to make the overall impedance lower so more power can be delivered to the "resistive" bit, i.e. more energy into the fluid for the same drive voltage. 2. It will act as a high impedance to the harmonics of the drive frequency, so while their voltages are present, the FETs don't consume any current at these frequencies, so a, their dissipation is lower and b, less power is consumed from the power supply.
The normal way to select the coil would be to put a small resistor (1 ohm?) in series with the transducer and swing the drive frequency for maximum AC volts across the resistor (transducer at resonance) then adjust the inductor for a maximum (additional capacitance now tuned out). As your kit is connected to the mains this method would seem dangerous. You could put a higher value resistor say 20 ohms in series with the transducer and rig up a diode detector with a meter (suitablely insulated) instead.
Frank