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The capacity of concrete beams will decrease by many external factors. To find simple and reliable method to monitor the quality of concrete beams is a challenging task. An optical-based fiber sensors is very interesting to develop for such task because of its many advantages. In this study, the optical fiber sensors were embedded in reinforced concrete beams to detect and to monitor deflection of the beam where a straight-line configuration of optical fiber was used. We perform experimental work to test performance of the use of optical fiber sensor by collecting data from flexural testing the concrete beam with the Universal Testing Machine (UTM). While the concrete deflection was measured by (linear variable differtial transducer (LVDT) as elongation unit, the fiber optic sensor output was observed in volts unit. We test the sensitivity of the optical fiber sensor by analyzing the relationship graph between the changes in the deflection of the concrete beam and output voltage of optical fiber sensors. The results show that optical fiber sensors have good sensitivity to detect and monitor concrete beam deflection.

A current source type power inverter is an inverter converting the dc current source to be ac current with magnitude, frequency and phase angle can be controlled. In a voltage source inverter, a short circuit condition is prohibited, because an excessive current may destroy the inverter circuits. In contrast, because inductors are used as energy buffer, an open circuit must be avoided in the operation of a current source inverter. In order to operate inverter properly, overlap-time is attached in the firing signals of power switches to avoid open circuit condition. However, adding overlap-time will generate distortion of the ac output current. Hence, compensation of overlap-time is absolutely needed for current source inverter to output high quality current waveform. A new overlap-time compensation method for current source inverter is proposed in this paper. The method utilized triangular carriers and sinusoidal signal for modulation strategy to generate gating signals of inverter with overlap-time compensation capability. The new method was examined using computer simulations. Further, experimental tests of inverter circuits applying overlap-time compensation method were also presented and discussed. The test results verified that the proposed method worked well suppressing distortions and harmonics of the ac current waveform caused by the overlap-time.

The design of a 1 kW buck-boost chopper with proportional-integral (PI) control is presented and discussed in this paper. The buck-boost chopper was proposed as a photovoltaic power converter to achieve a stable dc output voltage. In the design, the circuits employed IGBT power switch to function the PWM control signals to adjust the chopper’s output voltage. The circuits were tested to investigate the output waveform set at 24 V from various dc input voltage values. The chopper circuits were connected to ten solar PV modules with a total capacity of 1 kW. Simulation test results confirmed that the system was able to output 24 dc voltage with output current about 41 A. Furthermore, a prototype of the buck-boost chopper was set up and tested. The circuits worked well to output a stable 24 V DC voltage from PV output voltage varied 15 V-32 V.

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