As a rule, piezo transformer has a form of a plate or a bar, where the main resonance frequency oscillations or external mode longitudinal oscillations along the piezo transformer length are excited. The resonance frequency is dictated by a piezo transformer design and properties of the piezo ceramic material. The resonance frequency of the longitude mode oscillations is defined by the following expression:

f_res = m N/L , where:

m - mode number of excited oscillations
N - frequency constant of the piezo ceramic material (Hz.m)
L- piezo transformer length (m)

The value of N varies for different piezo ceramic materials from 1700÷2300.
Depending on application of a piezo transformer in the equipment, two methods of its mounting are possible.
  The piezo transformer located inside the equipment, which is protected from the influence of environment, is usually mounted on a special mounting film.
  When the transformer is mounted outside the equipment, as well as in the equipment not providing its reliable protection from environment influence, the piezo transformer is mounted in a special case, which ensures its protection from mechanical and other factors during its operation.
When the piezo transformer is mounted on a plate or in a case, the terminals should be soldered to the transformer. Soldering wires (diameter > 1.5 mm) is made by the solder of ПСр 2.5 type with ФКСП flux. To minimize the effect of heating on piezo transformer properties, the heating time should be 3 sec, max. The heating temperature should not exceed ºC. To fix the location of soldering, it is recommended to cover the place of soldering with glue K-400.
Piezo transformer is an acousto-mechanical resonator and therefore to minimize the effect of mounting on its parameters, it should be fixed only in certain points. The diagram of distributing oscillations in a piezo transformer shows that effect of mounting is minimized, when a piezo transformer is fixed in two points at the distance L from the end surfaces.

Mounting piezo transformer on a plate.

To mount the piezo transformer on a plate, a ring rubber pads having the width of 2 - 4 mm and the thickness of 1 - 2 mm are used (the diameter is dictated by the piezo transformer external dimensions and should ensure the tight mounting on a plate).

After mounting two pads at the distance ¼ L, they are fixed to the plate by two cramps. It is possible to use as a cramp ø 1.5-2 mm wire, which ends are soldered to the plate.

Mounting piezo transformer in a case

When a piezo transformer operates in conditions with low heating, it is recommended to use plastics or plexiglass as materials for its case. To facilitate mounting and wiring of a piezo transformer, it should consist of two parts: a base, to which the piezo transformer is fixed and where the wiring of electrical contacts is made, and a cover, which is used later for sealing the case. As a rule, electrical terminals are mounted on the end surface of the base. The case constitutes a four-pole network with two input terminals on the left and two output terminals on the right. Depending on the design, an input excitation circuit, including a high-frequency generator, can be housed in the same case. The piezo transformer is attached to the case by two rubber pads. The pads are fixes in the case slots or are clued both to the transformer and the case. The distance between the piezo transformer end surface and the pad should be about ¼ L. In order to increase mechanical strength, it is possible to fix the rubber pads by special cramps. The design and the form of the pads are similar to the ones used for mounting a piezo transformer on a plate. After mounting the piezo transformer and soldering its contacts, the base is closed by the cover and sealed by a screw joint or a hermitic composition. When a piezo transformer operates in conditions with considerable heating, it is recommended to use a case made of a light material. The gap between the piezo transformer and the case should not exceed 1 to 1,5 mm. The metal case also requires additional insulation of terminals from the case.

Pizo transformers mounted in a case by rubber pads stand the following tests:

Vibrations with frequency up to 2500 Hz and acceleration up to 25 g;

Linear acceleration up to 100 g;

Multiple shocks with acceleration up to 100 g;

Single shocks up to 500 g;

These recommendations are given for information only and should be specified for each case of a particular application of the piezo transformer in equipment and operating conditions.

Transformers.