Pi Type Ferrite Magnetostrictive Vibrators

Product catalog summary

Introduction to Magnetostriction Vibrators
Magnetostriction involves dimensional changes in ferromagnetic materials when magnetized. TDK's V2X Series uses this to produce ultrasonic waves, offering unique characteristics compared to metal vibrators.

Features

High electro-mechanical energy conversion efficiency (85-90%).
Minimal eddy current loss due to high specific resistance.
No need for DC bias due to ferrite magnet usage.
Excellent anticorrosive properties, suitable for various solvents.

Applications

Ultrasonic cleaning
Sonar
Ultrasonic machining

Product Identification

Material name
Ferrite magnetostriction vibrator
Type and resonant frequency
Shape classification code

Material Characteristics

Temperature dependence of resonant frequency: 17×10^-5 1/°C
Motional impedance: 180 Ω
Quality factor: 350
Electro-acoustic efficiency: 90%
Electro-mechanical coupling factor: 18%
Maximum input power (water load): 10 W/cm²
Continuous input power (water load): 3 to 5 W/cm²

Resonant Frequency Deviations
Frequency deviations are color-coded for matching sets, with ranks potentially changing based on production.

Conformity to RoHS Directive
Complies with EU Directive 2002/95/EC, avoiding harmful substances except for exempted applications.

General Characteristics

Excitation and Driving: Utilizes the Joule effect for vibration, achieving maximum amplitude at resonant frequency.
Vibrator Life: Virtually permanent under appropriate conditions, with guidelines for temperature and bonding.
Corrosion Resistance: Ferrite vibrators resist corrosion in various liquids, though caution is needed with coil and magnet elements.

Applications in Ultrasonic Cleaners

Vibrator Selection: Ferrite vibrators are preferred for stability and cost.
Frequency Selection: Typically 28kHz for large-scale cleaners, 40-50kHz for smaller ones.
Cleaner Power: Relation between tank volume and oscillator output is crucial.
Input Power: Calculated based on load conditions, with guidelines for maximum allowable amplitude and stress.

Vibrator Arrangement and Impedance Matching

Proper arrangement ensures uniform load impedance and effective vibration.
Impedance matching is essential for optimal vibrator performance.

Impedance Determination for Vibrators
To determine the correct impedance for a vibrator, consider the medium generating ultrasonic waves, the radiating surface, support, temperature, amplitude, and cavitation. Three excitation methods affect matching impedance: parallel resonance (fa), series resonance (fr), and fm excitation, each with different circuit configurations and load impedance calculations.

Excitation Methods

Parallel Resonance (fa): Involves adding a capacitor to resonate with damping inductance, leaving only the resistance component.
Series Resonance (fr): Adds series capacitance to cause resonance with the vibrator’s damping inductance.
fm Excitation: Practical for maintaining constant impedance despite load fluctuations, often matched with the frequency generating intense cavitation.

Securing the Bias Magnet
Magnets can be secured using rubber-based or epoxy adhesives. Care must be taken to prevent contact with the vibrator, as this affects precision and resonant frequency. Mechanical strength may require additional support, ensuring no direct contact with the vibrator.

Ultrasonic Cleaning Applications
Ultrasonic cleaners come in various types, with 28kHz π-shaped vibrators suited for industrial use. Lower frequency vibrators are effective for large objects. Water is the preferred cleaning liquid, with detergents enhancing performance. Proper setup ensures efficient cleaning, avoiding attenuation of ultrasonic waves by using large mesh sizes.

Other Applications and Precautions
Vibrators are also used in fish detectors and ultrasonic machining tools. Handling precautions include avoiding impacts, not operating in open air, and ensuring correct magnet polarity. Closed cell sponges are recommended to prevent water absorption and maintain a loadless condition.

Catalog excerpts

Pi Type Ferrite Magnetostrictive Vibrators-4

Fig.5 Cleaner tank volume and oscillator output > 123 Cleaner tank volume( ) 1 100100050010550 Oscillator output(W)205010010005005000 Fig.6 Examples of loads(a) Heavy load(b) Light load (deep liquid)(c) Light load (shallow liquid) > VibratorRadiating surface area (cm > 2 )Maximum allowable input power with water loadMaximum allowable amplitudeMaximum allowable stress(kg/cm m)p-p20kHz > 2 )Light loads (W)Heavy loads (W)( Տ type134080715028kHz type82550540kHz type82550450kHz type82550375kHz type3.510202100kHz type2.15121.5 Fig.7 Node position of > 2 -shaped vibrator > C Node

Open the catalog to page 4

Pi Type Ferrite Magnetostrictive Vibrators-6

(6/9) 002-02 / 20080108 / e171.fm (9) Impedance MatchingThe vibrators will not vibrate if their impedance is not matched.If they are not matched, the vibrators Q - which constitute loads in an output matching circuitҒs design - would be high, preventing the impedance to vary significantly near the resonant frequency and cause the Q to be different from the resistance load because the vibrator has the impedance.Such problems can be resolved by adjusting the vibrators impedance using coils and matching it with the oscillatorҒs output impedance.The following table shows actual examples. Actual impedance...

Open the catalog to page 6

Pi Type Ferrite Magnetostrictive Vibrators-8

(8/9) 002-02 / 20080108 / e171.fm Another method is to secure the magnet onto bakelite or nonmag-netic metal using epoxy adhesive as shown in Fig.19. Rubber-based adhesives are not suited for this purpose. Another point to remember is that a plate must be inserted on the upper side (as shown in broken lines in the figures) in situations where mechanical strength is required. When doing so, a gap must be created or a sponge must be inserted so that the plate does not directly contact the vibrator. > Fig.19 Securing the magnet using an epoxy adhesive NNSNNGap or spongeSecure magnet on bakelite...

Open the catalog to page 8