## 3 Experimental Verification
### Experimental Results  
Because the actual current data fluctuates greatly, the low-pass filtering is carried out in order to observe more clearly. The experimental results are shown in Figure 7 and Figure 8. With the passage of time, the train has experienced the process of static suspension, acceleration, deceleration, and static suspension. Moreover, during the period of 30-50 s, the train is running at the maximum speed (about 60 km/h). When the train moves forward at speed \(v\) in the direction shown in Figure 6, point 2 of the suspension module 101 is at the front and point 1 is at the rear.  
Figure 5: Tangshan maglev experimental line.  
Figure 6: Data acquisition position.  
It can be found that the influence of eddy current on the suspension system is reflected in the change of the suspension current. Furthermore, the electromagnet at the front of the train will increase the current to compensate for the attenuation of the suspension force caused by the eddy current effect, while the electromagnet at the rear is the opposite. Therefore, the change rate of the suspension current \(\Delta_{I}\) can be used as an index for studying the influence of the eddy current effect. Moreover, the larger the change rate, the greater the influence of the eddy current on the suspension system.  
By observing the variation curve of the empty-load current of point 2 in Figure 8, it can be obtained that: (1) In the period of 30-50 s, that is, when the train runs at the maximum speed (about 60 km/h), the current in point 2 is the largest, about 34.5 A. At this time, the induced eddy current intensity in the rail is the largest. (2) In the period of 90-100 s, that is, when the train is in static suspension, the current in point 2 is the smallest, about 27 A. At this time, there is no induced eddy current in the rail. It is worth noting that these  
Figure 8: Experimental data of current value (the point 2 of the suspension module 101).  
Figure 7: Experimental data of current value (the point 1 of the suspension module 101).  
two current data are consistent with the experiment data of the Changsha maglev line [25]. Then the change rate of the suspension current \(\Delta_{I}\) can be obtained as  
\[\Delta_{I}=\frac{I_{max}-I_{min}}{I_{min}}=\frac{(34.5-27)}{27}\approx 27.78\% \tag{7}\]  
This result means that the current of point 2 increases by 27.78% when \(v\) = 60 km/h compared with that when \(v\) = 0 km/h.  
Further, let \(\Delta_{F}\) represent the change rate of the suspension force. Thus, through Formula (5) can get  
\[\Delta_{F}=\frac{F_{max}-F_{min}}{F_{min}}=\frac{\frac{\mu_{0}SN^{2}I_{min}^{2} }{4\delta^{2}}-\frac{\mu_{0}SN^{2}I_{max}^{2}}{4\delta^{2}}}{\frac{\mu_{0}SN^{2 }I_{min}^{2}}{4\delta^{2}}}=\frac{(27^{2}-34.5^{2})}{34.5^{2}}\approx-38.75\% \tag{8}\]  
This result means that the suspension force decreases by 38.75% when \(v\) = 60 km/h compared with that when \(v\) = 0 km/h.  
Then the results shown in Table 2 can be obtained. It can be seen from Figures 7 and 8, and Table 2 that the variation of the suspension current is related to  
(1) the speed;  
(2) the load, that is positively correlated with the suspension current required.  
Because the variation of current in the experiment is caused by the eddy current effect, it can be said that the eddy current effect is related to the speed and the load or the suspension current required.