Abstract
The 4-leg inverter can adjust the load current or output voltage even under unbalanced load conditions, but it is known that the additional switch arm to the 3-leg inverter can increase the overall cost and the failure rate. This paper aims to analyze the failure rate and mean time between failures (MTBF) of 3-leg inverters and 4-leg inverters using part count failure analysis (PCA) and fault-tree analysis (FTA), and to compare the price of the inverters. The FTA can analyze the failure rate, including the type, number and connection status of the circuit components, and moreover the redundancy effect of the 4-leg inverter. For more accurate failure-rate prediction, the failure rate and MTBF of the 4-leg inverter according to the lifecycle of the controller are analyzed. Finally, by comparing the price of 3-leg inverters and 4-leg inverters using the cost model of major parts, the degree of reliability improvement against price increase is quantitatively analyzed.
Highlights
Compared with 3-Leg Inverters.An inverter is a power converter that converts DC into AC, which allows simultaneous control of output voltage and frequency, and is used for various purposes such as motor drives based on VVVF and grid-connection based on CVCF control
The reliability and economics of three-phase 3-leg and 4-leg inverters are analyzed in this paper by using the fault-tree analysis (FTA) technique, which can consider operational characteristics according to the redundancy characteristics of the 4-leg inverter
This study aims to accurately predict reliability according to the driving environment by analyzing the failure rate and mean time between failures (MTBF) by designing the fault-tree reflecting the operational risk according to the 3-leg and 4-leg inverter structure and control method
Summary
Various modulation techniques are being studied because of the advantages of increasing DC-link voltage utilization [8,9,10] and the presence of 16 switching states, enabling output voltage adjustments for unbalanced loads and control of energy flow for each phase [11,12,13,14,15,16,17,18]. The reliability and economics of three-phase 3-leg and 4-leg inverters are analyzed in this paper by using the fault-tree analysis (FTA) technique, which can consider operational characteristics according to the redundancy characteristics of the 4-leg inverter. This study aims to accurately predict reliability according to the driving environment by analyzing the failure rate and MTBF (mean time between failures) by designing the fault-tree reflecting the operational risk according to the 3-leg and 4-leg inverter structure and control method. Through the economic analysis of 3-leg and 4-leg inverters, the overall cost is compared to the effect of reliability improvement
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