Study on Seismic Performance of a Mold Transformer through Shaking Table Tests

Abstract

This study presents an experimental seismic investigation of a 1000 kVA cast resin-type hybrid mold transformer through tri-axial shaking table tests. The input acceleration time histories were generated in accordance with the specifications recommended by the International Code Council Evaluation Services Acceptance Criteria ICC-ES AC156 code, with scaling factors in the range of 25–300%. The damage and the dynamic characteristics of the mold transformer were evaluated in terms of the fundamental frequency, damping ratio, acceleration time history responses, dynamic amplification factors, and relative displacement. The shaking table test results showed that the damage of the mold transformer was mainly governed by the severe slippage of the spacers and the loosening of the linked bolts between the bottom beam and the bed beam. In addition, the maximum relative displacement at the top beam in Y and Z-directions exceeded the boundary limit recommended by the Korean National Radio Research Agency. Moreover, the operational test of the specimen was performed based on the IEC 60076-11 Standard before and after the shaking table test series to ensure the operational capacity of the transformer.

Experimental Investigations of the Seismic Performance of a Base-Isolated Uninterruptible Power Supply (UPS) through Shaking Table Tests

“…is shaking table reproduces earthquake input ground motions through a system of eight hydraulic actuators. Table 2 presents the specifications of the shaking table [11].…”

“…In contrast, the use of a vibration system consisting of spring isolators and incorporating snubbers could retain the spring isolators in the elastic stage, and the vertical restrained rods were not damaged. Dinh et al [11] experimentally investigated the seismic performance of an electrical mold transformer through tri-axial shaking table tests.…”

Seismic Vulnerability Assessment of Hybrid Mold Transformer Based on Dynamic Analyses

“…The accuracy of the aforementioned analytical modeling approach was assessed by comparing the analytical results to the experimental data from the shaking table tests [27]. In the shaking table test, the input acceleration-time histories were generated based on AC156 code for nonstructural elements [24].…”

“…When correlating the performance levels and damage states, the values of the limit states were defined for each target performance level corresponding to the damage states. The parameters by which the limit states were evaluated were partly based on the observation from shaking table test results [27] and partly based on judgment. Specifically, for the DS1, the peak response acceleration at the coils (PRA) in the Y-direction is strongly related to the spacer damage due to the fact that the lowest effective stiffness is in this direction.…”

“…Accordingly, the values of the limit states corresponding to the OP and PR performance levels were determined to be 50 mm and 75 mm, respectively, based on the provisions as well as the recommendations of the Korea Research Institute [43]. For the DS3, the maximum displacement in the Z-direction at the bottom beam is strongly related to the degree of loosening of the link bolted between the bottom beam and bed beam; and the values of the limit states corresponding to the OP, PR, and LS performance levels were determined to be 2.2 mm, 6.6 mm, and 12.45 mm, respectively, based on the experiment test results [27]. The summary of the value of the limit state corresponding to each damage state is presented in Table 6.…”