2 nd International and 17 th National Conference on Machines and Mechanisms iNaCoMM2015-148 Vishal Bagade Swithgear R&D, Crompton Greaves Ltd, Nashik, Maharashtra, India, E-mail: vishal.bagade@cgglobal.com. 1 Optimization of High Voltage Circuit Breaker Mechanism Design using Six Sigma Methodologies Vishal Bagade Abstract The functions of circuit breaker spring operating mechanism are identified as closing spring charging, closing operation and opening operation. Suitable mechanisms for these identified functions are discussed based on gear, linkage, cam, and intermittent motion elements. This paper presents the structural synthesis of opening mechanism considering the higher pair joints which results in several combinations of mechanisms. The focus of this work is on the design of opening mechanisms that open with high velocity using minimum opening spring energy. Two six-bar linkages are selected for detailed evaluation, one based on Watt’s mechanism and the other on toggle linkage. The toggle linkage is considered with link lengths, mass and inertia same as that of the Watt’s mechanism. This enhanced the opening speed by 30% for the same amount of input i.e. opening spring energy. Effect of different parameters, such as spring stiffness, compression, stroke, rotation of the lever, the initial angle of the lever, on opening speed is studied. The range of each parameter for optimization process is finalized. Plackett-Burman design in the design of experiments (DOE) is used to eliminate the non-significant factors. Then a full factorial DOE is conducted on the vital factors to maximize the opening speed. 20% enhancement is achieved in the opening speed after optimization for the same opening spring energy. The optimized toggle mechanism exhibits 50% higher the opening speed than the Watt’s mechanism for the same opening spring energy. Keywords: Circuit breaker mechanism, Structural synthesis, Watt’s mechanism, and DOE (design of experiments), Plackett-Burman design, full factorial DOE, Optimization 1 Introduction Circuit breakers are crucial devices in an electrical substation. They are essentially switches that break (i.e., open) an electrical circuit manually or automatically to protect against faulty conditions. A circuit breaker should also be able to connect the circuit back (i.e., close) after normal conditions are restored. This is achieved in circuit breaker mechanisms with the help of potential energy stored in opening and closing springs. This warrants quick closing and opening of the circuit breaker contacts. The operation of a circuit breaker mechanism is divided into three stages: charging the closing spring, closing the contact, and opening the contact. The focus of this paper is on the study of dynamic characteristics of opening mechanism. The status of springs, links, and latches in closing and opening operations is illustrated in Table 1. Changing the status of six different parts shown in the table is achieved with mechanism topologies that connect them.