The electromagnetic bearing

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Magnetic bearing is a kind of controllable electromagnetic force generated by electromagnet make rotor suspended in a magnetic bearing with a contact in the air gap between stator and rotor of new bearing. Compared with the traditional mechanical bearing, magnetic bearing has no friction, long life, simple without lubrication and maintenance etc, and has been widely used in vacuum and super clean room technology, turbomachinery, centrifuge, high-speed machines, high-speed motor, generator, flywheel energy storage device as well as the spacecraft attitude control of gyro, and other fields. The electromagnetic bearing In the electromagnetic bearing control system, the role of the power amplifier is to provide the corresponding to the magnetic bearing coil current to produce electromagnetic force that is needed. Electromagnetic bearing switching power amplifier for magnetic bearing control system of the actuator, seriously affect the stability of the electromagnetic bearing control system, the model precision of electromagnetic bearing switching power amplifier is also becomes the key to magnetic bearing control system stability analysis. The analysis of magnetic bearing control system, the model of the switch power amplifier is usually to equivalent with first-order inertia link. To equivalent electromagnetic bearing switching power amplifier with linear model, although can simplify the model of switch power amplifier, but electromagnetic bearing switching power amplifier is essentially a nonlinear link, therefore, switch power amplifier with first-order inertia link equivalent electromagnetic bearing model, switch power amplifier is difficult to guarantee the precision of the model. The authors in the literature on this problem, based on the electromagnetic bearing MATLABISIMULINK switch power amplifier power system simulation model, through the simulation of power system model were compared with the experimental results, confirmed that the power system simulation model can accurately reflect the actual characteristics of the electromagnetic bearing switching power amplifier. While using power system simulation model can solve the problems of the electromagnetic bearing switching power amplifier model precision, but the downside is that model of power system simulation model is complex, not intuitive, is easy to use mathematical language to describe. The electromagnetic bearing Magnetic bearing switching power amplifier for power system simulation model of this shortcoming, based on the reference [sichuan harmonic modeling of fluid pulse width modulation control system based on the electromagnetic bearing switching power amplifier of the harmonic modeling method is proposed, the model is simple and easy to practical. Harmonic model for simulation of the switch power amplifier, and the power model proposed in the literature and the results of simulation and experimental results are compared, the results show that the switching power amplifier harmonic model can more accurately reflect the characteristics of the switching power amplifier, as well as the stability of magnetic bearing control system analysis provides an important reference value. The electromagnetic bearing Use of permanent magnet biased magnetic field to replace the bias magnetic field generated by the bias current, not only can reduce the bearing heating, simplify the structure of bearing, but also can eliminate the bias current loss in the switching power amplifier, so the permanent magnet biased magnetic bearing is an important research direction of the magnetic bearing. The electromagnetic bearing Aiming at the application of permanent magnet biased magnetic bearing, magnetic bearing switching power amplifier main circuit requires a full bridge circuit, as shown in figure 1 in this way can the electromagnetic bearing switching power amplifier for magnetic bearing coil to provide two-way flow of current. R and L respectively equivalent resistance and inductance of coil electromagnetic bearing, U for dc bus voltage power supply. According to the circuit of the whole bridge four power switch tube n}} VT4 conduction and shut off to control different PWM generator of electromagnetic bearing switching power amplifier is usually divided into two level PWM generator and three level PWM generator. Pulse width modulation (PWM) control system of the electromagnetic bearing switching power amplifier, a simplified block diagram. The electromagnetic bearing