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Open AccessArticle

Effects of Electric Circulation on the Energy Efficiency of the Power Split e-CVT Hybrid Systems

Department of Vehicle Engineering, National Formosa University, Yunlin 63201, Taiwan
Undergraduate Program of Vehicle and Energy Engineering, National Taiwan Normal University, Taipei 106, Taiwan
Author to whom correspondence should be addressed.
Energies 2018, 11(9), 2342;
Received: 8 August 2018 / Revised: 24 August 2018 / Accepted: 3 September 2018 / Published: 5 September 2018
(This article belongs to the Section Energy Storage and Application)
This paper aims at investigating the fundamental characteristics of energy efficiency for power split electronic-continuously-variable-transmission (e-CVT) hybrid systems under the operation of electric circulation, i.e., circulating part of the engine power through the generator and motor in form of electric energy to improve system efficiency as well as perform the continuously-variable-transmission (CVT) functionality. The relations of kinematics and energy conservation for each power component are constructed and analyzed to classify how the operating points of the engine in term of torque and rotational speed may vary under different degrees of electric circulation indicated by a parameter called ratio of circulating power. Thereby, power split e-CVT hybrid systems can be classified into three types: upward circulation, downward circulation, and neutral circulation. Accordingly, two power split e-CVT hybrid systems, one of input split type and the other of output split type, are selected to be analyzed regarding their operating characteristics and simulated on their performances of energy efficiency. As a result, the former is a type of downward circulation in favor of driving at low speed and high driving load, while the latter is a type of upward circulation with an advantage of driving at high speed and low driving load. Thereby, applying this analysis to investigate the effects of electric circulation on power split e-CVT systems may help the developers implement suitable energy management and control strategy in accordance with their corresponding operating characteristics of energy efficiency. View Full-Text
Keywords: hybrid system; energy management; power split e-CVT; electric circulation hybrid system; energy management; power split e-CVT; electric circulation
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Chung, C.-T.; Wu, C.-H.; Hung, Y.-H. Effects of Electric Circulation on the Energy Efficiency of the Power Split e-CVT Hybrid Systems. Energies 2018, 11, 2342.

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