A vibration machine that drives an object to move by the electromagnetic force generated by the interaction of a constant magnetic field and a coil winding (supported on a spring) in the magnetic field is called an electro-dynamic shaker. The electro-dynamic shaker is currently the most widely used in environmental and reliability testing. The most efficient vibration testing equipment.
Compared with various types of vibration testing equipment, electro-dynamic shaker have many unique advantages:
a) Wide frequency range: the low frequency of the electro-dynamic shaker can reach below 1Hz, and the high frequency can reach 5kHz or even higher;
b) Large amplitude: The displacement of the electro-dynamic shaker is usually ±25mm. The peak-to-peak displacement of the electro-dynamic shaker used for impact testing can reach 100mm. To meet special needs, a longer peak-to-peak stroke can also be achieved.
c) Large excitation force: the thrust force of the electro-dynamic shaker can be as small as a few hundred Newtons or as large as hundreds of thousands of Newtons;
d) Small waveform distortion: various types of vibration tests can be realized, such as broadband random, sine + broadband random, narrowband random + broadband random, transient waveform reproduction, etc.
Working principle of electro-dynamic shaker
The core parts of the electro-dynamic shaker are the excitation winding that passes DC current and the moving coil winding that passes AC current. The moving coil winding is suspended in the annular gap in the closed-loop magnetic circuit of the excitation winding.
According to the principle of electromagnetism, if DC current is passed through a wound coil, the coil becomes a magnet according to the “right-hand spiral rule” (Figure 1), and a closed-loop magnet is formed through the magnetic conductive material connected to the coil. path, an air gap is intentionally cut in this closed-loop magnetic circuit. Since the air in the air gap has a much greater magnetic resistance than the magnet, the magnetic field lines in the middle section of the air gap will continue to pass forward, while the magnetic field lines at the edge of the air gap will continue to pass forward. There is arc-shaped divergent leakage. The wider the air gap, the greater the magnetic resistance and the greater the magnetic circuit leakage. Therefore, the air gaps of the electric vibrating table are all very narrow annular gaps. If a energized coil (moving coil winding) is placed in this annular air gap, according to the “left-hand rule” of the magnetic field on the energized conductor (Figure 2), the energized moving coil winding will move under the action of electromagnetic force. , if the moving coil winding is supplied with an alternating current signal, the energized moving coil winding will produce reciprocating motion – vibration.
