NdFeB magnet double magnet magnetic circuit2018-07-11
The appearance of a double magnet magnetic circuit
Devices such as televisions and recorders cannot be separated from devices with magnetic circuits like speakers, but they cannot tolerate their stray magnetic fields. This stray magnetic field can distort the image and color of the color TV set and also adversely affect the recorder.
The inner magnetic magnetic circuit made of an alloy magnet can reduce magnetic flux leakage and has a small volume. But it brings a problem that cannot be taken seriously, that is, the cost is too high.
It is precisely because of this situation that the double magnetic ferrite magnetic circuit first appeared in Germany, which solved the contradiction between magnetic shielding, price and performance.
Structure and principle of double magnet touch
The magnetic flux distribution diagram of the two magnets shows that the magnetic field of the two magnets increases the magnetic flux density in the air gap and reduces the total magnetic flux.
About the magnetic line distribution of the double magnetic circuit:
(1) Similar to the single magnetic flux distribution.
(2) The magnetic flux distribution of the original magnetic circuit is increased.
(3) The magnetic leakage of the closed magnetic circuit is extremely small.
(4) The magnetic flux leakage resistance of the stray magnetic field is extremely large.
From practical and theoretical analysis, we can know:
(1) The auxiliary magnet will increase the magnetic flux in the air gap by 10% ~ 20%.
(2) The auxiliary magnet is magnetized in an open state, so it is desirable that its coercive force He is high.
(3) The magnetic conductive bowl provides a circuit with small magnetic resistance, which reduces the leakage magnetic flux and has a good shielding effect on the outside of the magnet. The larger the radius of the magnetic bowl, the better.
The dual magnetic circuit design can be designed separately for the main magnetic circuit and the auxiliary magnet, and then superimposed and corrected.
AC magnetic circuit
In order to limit the length of this book, the book does not intend to discuss magnetic circuits with excitation coils such as transformers. Here is a brief description of the AC magnetic circuit.
AC magnetic circuit: It includes two parts of AC and DC magnetic circuits, so the situation is more complicated. However, the principles and methods of the straight soul can still be used.
There are fixed magnetic fluxes generated by N and S magnets, and there is also an AC magnetic flux generated by alternating current.
The magnetic field is proportional to the square of the magnetic flux under the suction of the diaphragm. The 1 pass cannot be increased indefinitely. It is necessary to increase the magnet and the magnetic conductor to increase the elasticity and thickness of the vibration system, so that the weight of the vibration system increases and the electroacoustic performance is caused. It is getting worse.