# Three-Phase Unbalance Analysis Method Based on Three-Phase Motor Current Instantaneous Information
## 3 Simulation Analysis and Experimental Verification
### Experimental Validation and Analysis  
The main components of this section of the test bench are shown in Figure 25, which are mainly composed of an inverter, motor, phase controller, gearbox, magnetic powder clutch, and other components, of which the motor is replaceable. The current sensor was clamped to the motor power input, model Fluke i200 s, 100 mV/A range. The sensor data were collected using a NI-USB 9234 data acquisition card. The sampling frequency was 3200 Hz. The speed (rotational frequency) settings were 5 Hz, 10 Hz, 15 Hz, and 20 Hz. The fault motor is a motor with voltage unbalance and a single phase (abbreviated as MVUSP). Adjustment of the motor current three-phase unbalance is achieved by rotating the phase controller knob, gradually adjusting it up from small, then adjusting it down, and then repeating it once. The motor runs at 5 Hz, 10 Hz, 15 Hz, and 20 Hz, and the three-phase current signal obtained by adjusting the three-phase unbalance through the knob is shown in Figure 26. When the knob is rotated clockwise, the W-phase current amplitude decreases and the three-phase unbalance increases; when the knob is rotated counterclockwise, the W-phase current amplitude increases and the three-phase unbalance decreases. Figure 24: Results of instantaneous information after superimposing harmonics with a sliding window of 0.5 s: (**a**) instantaneous frequency; (**b**) instantaneous amplitude; (**c**) the C.V. of the instantaneous frequency; (**d**) the C.V. of the instantaneous amplitude. The segmented signals in different periods (0-1 s, 15-16 s, 21-22 s) at a 15 Hz rotational frequency are shown in Figure 27.  
Figure 25: Gearbox dynamics test bench: (**a**) composition of the experimental bench; (**b**) phase controller; (**c**) current sensor clamping. Figure 26: Three-phase current signal to adjust the degree of three-phase unbalance at different rotational frequencies: (**a**) 5 Hz; (**b**) 10 Hz; (**c**) 15 Hz; (**d**) 20 Hz. The sliding window size is 1 s. The instantaneous frequency and instantaneous amplitude at 15 Hz are shown in Figure 28. The results of the C.V. of the instantaneous information are shown in Figure 29. The results of the symmetrical components method are shown in Figure 30. Comparing Figures 29 and 30, it can be seen that the C.V. of the instantaneous frequency and the C.V. of the instantaneous amplitude have the same trend as the three-phase unbalance results calculated using the symmetrical components method as the 1 s sliding window. The C.V. of the instantaneous frequency and the C.V. of the instantaneous amplitude were calculated for the three-phase unbalanced signals at 5 Hz, 10 Hz, and 20 Hz rotational frequencies, respectively, with a sliding window size of 1 s. The results are shown in Figure 31. Comparing the C.V. of the instantaneous frequency, the C.V. of the instantaneous amplitude, and symmetrical components method coefficients at the same rotational frequency, it can be seen that they have similar trends and are consistent with the results at a 15 Hz rotational frequency. The above results show that both the proposed method and the symmetrical components method can reflect the change in the three-phase unbalance. Figure 28: Instantaneous information at a 15 Hz rotational frequency: (**a**) instantaneous frequency; (**b**) instantaneous amplitude. Figure 24:0 Three-phase current at 15 Hz rotational frequency of different periods: (**a**) 0–1 s; (**b**) 15–16 s; (**c**) 21–22 s.  
Figure 24:1 The results of the proposed method at a 15 Hz rotational frequency: (**a**) the C.V. of the instantaneous frequency; (**b**) the C.V. of the instantaneous amplitude. The effects of different sliding window lengths on the method proposed in this paper and the symmetrical components method are analyzed as follows. For the three-phase unbalanced signal at a 15 Hz rotational frequency, its single-phase signal period is \(1/15\) s (about 0.067 s).