# Three-Phase Unbalance Analysis Method Based on Three-Phase Motor Current Instantaneous Information
## 4 Conclusions  
This paper proposes a three-phase unbalanced analysis method based on the instantaneous information of the motor current. The basic process is as follows: obtain the three-phase current signal, construct the phase shift signal via vector demodulation to obtain the instantaneous frequency and instantaneous amplitude of the current signal, calculate its coefficient of variation, and compare and analyze the performance of instantaneous information characteristic coefficients under the three-phase unbalance condition.  
Simulation experiments are conducted to analyze the effects of amplitude deviation and phase deviation on the variation coefficients of the instantaneous frequency and instantaneous amplitude, respectively. The continuous change in a three-phase unbalance amplitude is simulated, and its instantaneous performance is analyzed. Compared with the symmetrical components method, the proposed method can still analyze the three-phase unbalance with a smaller sliding window size. Simulation results show that switching noise will affect the C.V. of the instantaneous frequency, while the C.V. of the instantaneous amplitude can still reflect the unbalance change trend. When harmonics are superimposed, the proposed method can still reflect the change in the unbalance trend for three-phase unbalance caused by changes in amplitude.  
The experimental verification analyzes the instantaneous frequency and instantaneous amplitude coefficient of variation characteristics when comparing and analyzing the continuous change of the three-phase unbalance of the motor at different speeds. Simulations and experiments show that the proposed method in this paper can analyze motor three-phase unbalance faults.  
Advantages: The instantaneous information of the three-phase current is obtained through Park vector demodulation, the calculation result is similar to the trend of the symmetrical components method, the time complexity of this method is smaller than that of the symmetrical components method, and a smaller sliding window is required.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**1 s Sliding Window**} & \multicolumn{2}{c}{**0.2 s Sliding Window**} \\ \cline{2-5}  & **The Proposed Method** & **The Symmetrical** & **The Proposed Method** & **The Symmetrical** \\  & **in This Paper (s)** & **Components Method (s)** & **in This Paper (s)** & **Components Method (s)** \\ \hline
5 Hz & 0.000238 & 0.010089 & 0.000078 & 0.002203 \\
10 Hz & 0.000175 & 0.010281 & 0.000079 & 0.002151 \\
15 Hz & 0.000218 & 0.010082 & 0.000084 & 0.002157 \\
20 Hz & 0.000276 & 0.010133 & 0.000072 & 0.002143 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The single sliding window calculation time at different rotational frequencies.  
**Author Contributions:** Conceptualization, X.Z.; Methodology, X.Z. and G.X.; Software, X.Z.; Validation, X.Z. and S.C.; Formal analysis, X.Z. and R.C.; Investigation, X.Z. and X.C.; Resources, X.Z. and G.X.; Data curation, X.Z.; Writing--original draft preparation, X.Z.; Writing--review and editing, X.Z., G.X., X.C., R.C., S.C. and S.Z.; Visualization, X.Z.; Supervision, G.X. and S.Z.; Project administration, G.X.; Funding acquisition, G.X. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was supported by the Key Projects in Shaanxi Province (Grant No. 2021 GXLH-Z-008), the Science and Technology Plan Project of Xi'an (Grant No. 20 KYPT0001-10), and the National Key Research and Development Program of China (Grant No. 2019 YFB2004400).  
**Institutional Review Board Statement:** The study did not require ethical approval.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data sharing is not applicable to this article.  
**Conflicts of Interest:** The authors declare no conflict of interest.