Isolation transformer

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

A Novel DC Current Injection Suppression Method for Three-Phase Grid-Connected Inverter Without the Isolation Transformer

Abstract: Due to current sensor errors, tolerance of power switching devices, and asymmetry of PWM gating driving pulses, grid-connected inverters without isolation transformer usually have certain amount of dc components injected to the ac grid. Many efforts, such as using a blocking capacitor, a current dc component feedback control, and a voltage dc component feedback control have been introduced to try to suppress the dc injection to the grid. This paper proposes a novel control strategy of suppressing dc current injection to the grid for a three-phase inverter by accurately sensing the dc component of line voltages of three-phase inverter and adding a dc component control loop. A dc suppression control scheme is presented, and the suppression performance of the proposed dc rejection method is evaluated and compared with the traditional method. Finally, the control scheme is verified on a 20-kW three-phase grid-connected inverter.

Control Power Self-Generation and Sensors Integration in Emitter Turn-off (ETO) Thyristor

Abstract: This paper highlights the design and demonstration of control power self-generation and integration in the emerging new power semiconductor switch emitter turn-off (ETO). It also discusses a method that is utilized to achieve complete sensor integrations in the ETO. Conventional high-power devices require dedicated external power supplies with isolation capability to operate. An isolation transformer lowers the system reliability and increases the cost of the power converter. At the same time, conventional converters rely on expensive external sensors to gather the voltage, current, and temperature information. The emerging ETO is a fully optically controlled power switch: The internal control power is self-generated; voltage, current, and temperature sensors are also integrated in the device.

Transformer modeling as applied to differential protection

Abstract: This paper presents a power transformer model to evaluate differential element performance. The paper analyzes transformer energization, overexcitation, external fault and internal fault conditions with this model. Test results with an actual transformer validate the model. The paper includes a guide for properly selecting current transformers for differential protection applications. Accurate power transformer modeling and proper current transformer selection leads to improved transformer protection.

Wide range regulated power supply utilizing optimized energy storage

Abstract: A fly-back type power supply includes a transformer, the primary winding of which is periodically connected to a DC source to establish current through such winding. When this current increases to a predetermined optimum value, the current flow through the primary winding is interrupted for producing collapse of the transformer''s magnetic field and generation of an output in the transformer''s secondary windings. The frequency at which the primary is periodically connected to the DC source is controlled by a secondary output voltage such that the frequency is increased when such output voltage tends to decrease. A plurality of secondary windings are each connected to a rectifier and filter capacitor combination, wherein the filter capacitors are coupled in series for production of a high voltage output.

A 10kW transformer with a novel cooling structure of a contactless power transfer system for electric vehicles

Abstract: A contactless power transfer system for electric vehicles is required to have high efficiency, a large air gap, good tolerance to misalignment in the lateral direction, and to be compact and lightweight. A new 10kW transformer with double-sided winding for fast charging has been developed. The proposed transformer has a novel cooling structure using aluminum bars, aluminum junctions, and aluminum plates. In this paper, the design concept, specifications, and test results of the new transformer are described. The other feature of this transformer is its interoperability with a 3kW transformer. The interoperability test results are also shown.