Electrodynamic converter with efficient cooling


Created on 16.10.2019 23:21.

Updated 10.16.2019 23:37.

Author: Gorobtsov V.M.

The invention relates to electromechanical converters. In an electrodynamic converter with effective cooling, consisting of a magnetic circuit with an annular gap formed by its poles, a power (voice) coil is located. The coil can be moved by the action of the alternating current flowing through it.

The surfaces of the poles that form the annular gap are covered with a material with a higher thermal conductivity than that of the magnetic circuit. In this case, the heat exchange surfaces in contact with the air in the gap are rough and contain grooves.

In a particular case, the grooves can be made in the form of a lattice with inclined longitudinal components. As a result, the thermal regime in the “power (voice) coil – magnetic circuit” unit is improved and, as a result, the reliability and durability of its operation increases.

Rice. 1. Design of an electrodynamic loudspeaker with effective cooling

The essence of the invention is illustrated by the drawing, which shows an electrodynamic transducer in section. The converter contains a core magnet or electromagnet 1, a magnetic circuit 2, a pole piece 3, an upper flange 4, a power coil frame 5, a power coil winding 6, an annular gap 7, grooves 8.

When the power coil vibrates in the annular gap 7, a multidirectional movement of the air medium occurs, which, under the action of the roughness (not shown) of the surfaces and grooves 8, acquires a vortex character, which leads to the destruction of the boundary layer on the heat exchange surfaces and provides a sharp intensification of the processes of heat transfer from the power coil and transmission thermal energy through the air to massive parts of the magnetic system.

In a classical electrodynamic transducer (dynamics), in which the magnetic field is concentrated in the annular gap, and the conductor is wound on a cylindrical frame in the form of a voice (power) coil. In the process of conversion, part of the electrical energy supplied to the power coil is converted into mechanical energy, and part is dissipated in the form of heat. A certain thermal contribution is also made by eddy currents (Foucault currents) arising in the near-surface parts (at a depth of about 0.5 mm) of the magnetic circuit during movement power coil. The temperature of the power coil and the elements of the magnetic circuit causes mechanical damage to the coil, changes in the magnetic properties of the circuit, and an increase in the active resistance of the winding wire.

To improve the thermal regime of the power coils, magnetic fluids, heat pipes, semiconductor refrigerators, materials for frames of power coils with high thermal conductivity, radiators on magnetic circuits, as well as special heat-resistant materials for frames, wire insulation and adhesives for coils, withstand heating up to 200– 300 ° C without change in properties. All these measures improve the thermal conditions of the power coils, but the cost of many of them is quite high.

The specified technical solution, in contrast to the known technical solution, allows:

  1. To significantly improve the thermal conductivity in the contact zone of the heat-conducting air medium with the heat-removing magnetic circuit, i.e. improve the conditions for convection heat transfer.
  2. Create a higher degree of turbulence in the annular gap, destroying the boundary layer on the heat exchange surfaces, and ensure the intensification of heat transfer processes.
  3. Reduce or eliminate the formation of eddy currents / Foucault currents / in the near-surface parts of the magnetic circuit.

Source: patent RU 2 131 163 C1 dated May 1999