จำนวน Repository ( 2 )
การศึกษาผลของกระแสฮาร์มอนิกส์ต่อค่าสูญเสียของหม้อแปลงไฟฟ้าเลื่อนเฟสและการทำให้เป็นจริงด้วยหม้อแปลงไฟฟ้าเลื่อนเฟส 15 องศา
The trend of energy savings has been widely interested and phase shift transformers (HMT) have been extensively used. This paper presents the investigation of the effect of harmonic currents on losses of the HMT. In this paper a 15-degree HMT with quad secondary winding is applied to find the relationship between harmonic currents and losses of the HMT. This relation can be met by testing the active power of primary and secondary sides while the HMT supplies for two and four non-linear loads at 25% 50% 75% and 100% rated currents respectively. The results reveal that harmonic currents affect winding eddy current losses significantly and the losses for loading the two secondaries 1 and 2 are the same as loading the two secondaries 1 and 3 while both %THDi are different. However for loading the secondaries 1 and 2 the %THDi is more than 15% so it is not met IEEE 519 Std. while the HMT is supplied with four loads the %THDi has met IEEE 519 Std. and the losses are less than 57% compared to one load. As a result of these if the HMT is applied to an adjustable speed drive system it is not only reduced the harmonics but also saved the energies.
การออกแบบสถานีวัดอากาศขนาดเล็กราคาประหยัดโดยใช้โปรแกรม LabVIEW
The objective of this research is to develop a small and low-cost weather station. The station will be wireless transmit and receive data via radio signals. The 45mW solar cell will be used as a solar irradiance sensor which is very expensive for the weather station and the PIC18F97J60 controller will control the transmitter and receiver system. Moreover the author has developed the weather monitoring software by using LabVIEW. After testing the measurement percentage errors with the reference weather station the results showed that the relative humidity measurement error is equal to 3.106% the temperature measurement error is equal to 0.685% the wind speed is about 4.527% the wind direction measurement error is equal to 5.236% and the solar irradiance measurement error is equal to 0.501%. The longest working distance between the weather sensor and receiver unit is equal to 145 meters.