# Research on Output Voltage Stability of Non-Contact Excitation Motor
## 3 System Topology and Principle  
Since the inductance in the primary coil will consume reactive power when resonance occurs, thereby reducing the transmission performance of the system, a compensation circuit needs to be added to compensate for the reactive power. Standard compensation circuits include series circuits and parallel circuits, adding a series circuit or similar to the primary side circuit, and adding a series circuit and a secondary side circuit to the secondary side circuit. This compensation method has a simple structure, and the output current and voltage are easy to calculate, but this has many shortcomings in the actual application process. As the load increases, so does the wind in the primary coil, causing more unnecessary losses and making the components more prone to burnout. Based on this, we adopt a high-order compensation method. The primary side uses a compensation circuit that combines inductance and capacitance. The compensation circuit of the secondary side is still a series capacitor. It is found through a calculation that the current in the primary coil is completely independent of the system load. The circuit model and calculation process are explained in detail below. The main circuit structure of the contactless excitation synchronous motor includes the following modules. The circuit topology is shown in Figure 4. The primary circuit consists of inductance \(L_{R}\), inductance \(L_{P}\), capacitors \(C_{1}\), \(C_{P}\), and resistance \(R_{P}\), in which inductance \(L_{R}\) and capacitor \(C_{P}\) form a resonant loop, and inductance \(L_{P}\), capacitor \(C_{1}\), and capacitor \(C_{P}\) form a resonant loop. At this time, the resonant frequencies of the two loops are equal. The secondary circuit includes inductance \(I_{S}\), resistance \(R_{S}\), and capacitance \(C_{S}\). At this time, inductance \(L_{S}\), and capacitance form a resonant circuit. The secondary circuit includes inductance \(I_{S}\), resistance \(R_{S}\), and capacitance \(C_{S}\). At this time, inductance \(I_{S}\) and capacitance \(C_{S}\) form a resonant circuit. When the resonant frequencies of the three courses are equal, electromagnetic resonance occurs in the circuit, and the energy in the primary circuit will be transmitted to the secondary circuit through electromagnetic resonance. The primary coil and the secondary coil transmit power through electromagnetic coupling. The brush on the traditional motor is banned, the wear of the meeting is avoided, and the motor works more stably. Figure 3: Porcelain tank transformer structure. \(R_{eq}\) is the equivalent resistance after full-bridge rectification, ignoring the loss of the rectifier. In the primary circuit, there are two resonant circuits, which are the resonant circuit composed of the inductor. Inductance \(L_{R}\) and capacitor \(C_{P}\) form the first resonant circuit. The other resonant circuit is where inductor \(L_{P}\) connects with capacitor \(C_{1}\) and then resonates with \(C_{P}\). The primary coil has two resonant circuits: In the secondary coil, capacitor \(C_{S}\) and inductor \(L_{S}\) form a resonant circuit, and the primary coil and the secondary coil resonate to meet the above frequency requirements. Therefore, capacitance and inductance, respectively, satisfy the following mathematical relationships:  
\[\omega L_{R}=\frac{1}{\omega C_{P}} \tag{1}\]  
\[\omega L_{P}-\frac{1}{\omega C_{1}}=\frac{1}{\omega C_{P}} \tag{2}\]  
\[\omega L_{S}=\frac{1}{\omega C_{S}} \tag{3}\]  
According to the above relationship between capacitance and inductance, resonance occurs in the circuit, and the energy in the primary coil can be transferred to the secondary coil through electromagnetic resonance. The equivalent impedance of the secondary circuit can be expressed as  
\[Z_{S}=R_{eq}+R_{S}+j\omega L_{S}+\frac{1}{j\omega C_{S}} \tag{4}\]  
where \(Z_{r}\) is the reflected impedance of the secondary side circuit to the primary side.