Isolation transformer

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

Modem with digital isolation

Abstract: The MODEM WITH DIGITAL ISOLATION removes the relatively large heavy isolation transformer from the Data Access Arrangement and substitutes two tiny pulse transformers between the Integrated Analog and Digital Signal Processor with multiplexers and demultiplexers to eliminate analog distortion and multiple leads, and to accommodate Lap Top/Palm Top computers, while enhancing data speeds. The combination with surge protection enables both uncommon and common mode protection.

Electrosurgical generator safety apparatus

Abstract: Leakage cancelling apparatus suitable for use in electrosurgery apparatus to prevent electrical burns is disclosed. The apparatus comprises a transformer which is connected in the electrical circuit between the electrosurgical source and the patient. The transformer has a primary winding connected in series with the active surgical electrode and a secondary winding connected in series with the return path to the electrosurgical generator. The connections to the windings are polarized so that during normal operation the magnetic fields in the transformer core generated by current flow are almost completely cancelled. Consequently, the transformer windings present very small impedances in series with the electrosurgical circuit. If a break occurs in the return lead of the electrosurgical circuit and the patient becomes ungrounded, a condition which would normally result in a high risk of a burn, the currents in the primary and secondary windings of the transformer become unequal, the magnetic fields in the transformer core do not cancel and the transformer windings present a significant impedance to the flow of electrosurgical current which reduces the occurence of electrosurgical burns. In addition, the uncanceled inductance presented by the transformer windings during a break situation may be chosen to resonate with the leakage capacitance of the electrosurgical circuit, further reducing the current flow and preventing burns.

Multilevel power amplifier architecture using multi-tap transformer

Abstract: A multi-level power amplifier architecture using a multi-tap transformer implemented on a single CMOS integrated circuit wireless communications device is described. By providing a multi-tap transformer for coupling a plurality of power amplifiers to a shared output impedance, such as an antenna, power transmission may be made at different levels while maintaining efficiency. With a multi-tap transformer having “N” taps featuring “N” different impedance levels, each tap may be connected to an amplifier cell which delivers power into the transformer at the tap for coupling to the output load. Any one of the “N” amplifier cells can be turned on at once along with any combination of the “N” amplifier cells.

LVRT Capability Enhancement of DFIG With Switch-Type Fault Current Limiter

Abstract: A low-voltage ride-through (LVRT) strategy for a doubly fed induction generator (DFIG) with a switch-type fault current limiter (STFCL) is presented in this paper. The STFCL is composed of fault-current-limiting inductors, isolation transformers, a diode bridge, a semiconductor switch, a snubber capacitor, and a fault energy absorption bypass. The presented STFCL can insert fault-current-limiting inductors in series with the stator branches on occurrence of a grid fault, which can limit the rotor overcurrent and weaken the rotor back electromagnetic force voltage simultaneously. The safety and controllability of the rotor side converter can thus be guaranteed. The STFCL can also absorb the excessive energy stored in the stator during LVRT with the fault energy absorption bypass so as to prevent the semiconductor devices from overvoltage. The feasibility of the proposed approach is validated by simulation studies on a typical 1.5-MW wind-turbine-driven DFIG system. The validity of the proposed approach is further verified by the experimental results on a 2-kW DFIG prototype.

A Wavelet-Based Transformer Differential Protection With Differential Current Transformer Saturation and Cross-Country Fault Detection

Abstract: The current transformer (CT) saturation phenomenon has been one of the main problems for the power transformer differential protection, leading to incorrect current measurements and relay misoperation. This paper proposes a fast and efficient transformer differential protection scheme with additional differential CT saturation and cross-country fault detection modules after the external fault detection, all of them based on the differential wavelet coefficient energy with border distortions in order to stabilize the relay during external faults and distinguish accurately CT saturation from cross-country internal faults. The proposed method was assessed by using representative simulations of internal faults, transformer energizations, and external faults with CT saturation followed by cross-country internal faults, and good results were achieved.