Isolation transformer

About: Isolation transformer is a research topic. Over the lifetime, 8145 publications have been published within this topic receiving 72396 citations.

Power supply operable on varying inputs

Abstract: A power supply provides the stable DC voltages needed for a computer terminal from a wide range of line voltages and frequencies. The line is rectified and fed to a flyback transformer wherein primary current is controlled in duration for providing the desired energy transfer to the secondary winding. The outputs from the flyback transformer are rectified and filtered. A separate start-up circuit uses a transformer across the line voltage, and a positive coefficient resistor provides a time limit to allow the use of a small transformer even though the line voltage may be high. The start-up circuit must produce a minimum voltage for the switching transistor in the flyback arrangement to allow operation of the power supply, and the start-up transformer is disconnected from the circuit after operation to prevent electromagnetic interference within the terminal. The output from the power supply is used in the control of the switching transistor so that, once the start-up circuit has achieved the needed voltage level, the power supply can assist in maintaining the operation.

Grounding transformer application, modeling, and simulation

Abstract: The grounding transformer is a transformer intended solely for establishing a neutral connection point on a three-phase ungrounded power system. The transformer is usually of the wye-delta or zig-zag transformer. This paper first reviews the state of the art of the grounding transformer to assist electric power engineers in the proper understanding of the use and applications of these devices, and then a zig-zag grounding transformer is modeled in PSCAD/EMTDC simulator. After a 27.6 KV ungrounded three-phase transmission system is constructed, different scenarios are simulated and verified under different conditions with the connection of the grounding transformer.

Development of a D-STATCOM prototype based on cascade inverter with isolation transformer for unbalanced load compensation

Abstract: This paper describes the distribution level static compensator (D-STATCOM) of three-phase three-wire distribution system for unbalanced load compensation First, a novel transformer-isolated multilevel H-bridges inverter is introduced, which is suitable for large unbalanced load compensation For solution to improve the power quality at the point of common coupling (PCC), the compensation scheme is proposed with dual d-q transformation and symmetrical components method In addition, the balancing design method is employed to equalize the phase currents of triangle connection transformer Then the computer simulation system is built with software PSCAD to test the functions of the D-STATCOM Finally, the hardware prototype is made based on two H-bridges voltage source inverter with 1700 V/75 A IGBT The switching frequency of the space vector modulation (SVM) PWM is set at 500 Hz to generate the compensation currents The DSP and FPGA based system is employed as the controller Simulation and experimental results are also given to validate the effectiveness of the proposed D-STATCOM

Pulse-controlled gate circuit with protection against short-circuit

Abstract: A pulse-controlled circuit for an insulate gate power transistor (Tp) comprises an auxiliary MOS transistor (T1) connected between the gate and a reference terminal of the power transformer in parallel with a pulse transformer secondary (W2). This circuit comprises two controlled unidirectionally conductive paths in parallel (D1, M1; D2, M2) between one terminal of the transformer secondary and the auxiliary transistor gate, these paths being alternatively rendered conductive when a positive or negative pulse is applied to the secondary of the transformer.

Stability analysis of air-core superconducting power transformer

Abstract: The air-core superconducting power transformer is being investigated as a transformer having the function of a shunt reactor. From the results of the authors' previous analysis, the magnetic field acting on the superconducting wires of an air-core transformer under load includes the rotating component besides the alternating component. Since this rotating component has a possibility of affecting the wire stability, the influence should be clarified. In this paper, a method of stability limit analysis based on the instantaneous magnetic field calculation is proposed. Quench tests of an experimental air-core superconducting transformer are carried out, and the stability limit of the air-core superconducting transformer is analyzed by using the proposed method. From the results of the analysis, it is seen that the load factor of the superconducting wire, which is defined in this paper, is almost the same regardless of the superconducting power transformer load.