A New Rapid-Response Hydraulic Actuator—Design, Analysis and Test Results

Abstract

This paper describes the development of a new hydraulic operator with rapid response (< 0.003 seconds) and high operating velocity (10 m/sec.) to be used in a high voltage DC circuit breaker [1]–[6] now under development [8]. A new “two-way” valve employs the eddy current repulsion principle for actuation and opens to 8 cm2 flow area within 0.0005 sec. By a novel exploitation of hydraulic fluid inertia, it has proven possible to achieve with only a single, directly-actuated “two-way” valve, plus a latch, the functions which normally require a pilot-operated “three-way” valve or two “two-way” valves. These features have led to a significant simplification, reduced response time and improved reliability of the hydraulic operator and the system it operates. The paper covers unique features of the hardware design, the analysis and the test results. On the basis of theory and test, the principle sources of time delay in the hydraulic system are identified and analyzed, leading to general design principles. Both closed form and numerical analytical solutions have been developed which are in excellent agreement with experiment. A systematic evaluation has been made of the relative merits of initiating motion by increasing the pressure above a piston as contrasted to decreasing the pressure below a piston in order to achieve the fastest response. Tests run over a wide range of ambient conditions and at hydraulic pressures up to 340 atm confirm the ability of the system to move masses of the order of 10 kg a distance of 2 cm with total response time approaching 2.5 milliseconds.