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Circuit diagram for open-circuit test. The open-circuit test, or no-load test, is one of the methods used in electrical engineering to determine the no-load impedance in the excitation branch of a transformer. The no load is represented by the open circuit, which is represented on the right side of the figure as the "hole" or incomplete part of ...
A short circuit is an abnormal connection between two nodes of an electric circuit intended to be at different voltages. This results in an electric current limited only by the Thévenin equivalent resistance of the rest of the network which can cause circuit damage, overheating, fire or explosion.
A different form of short-circuit testing is done to assess the mechanical strength of the transformer windings, and their ability to withstand the high forces produced if an energized transformer experiences a short-circuit fault. Currents during such events can be several times the normal rated current.
Transmission lines terminated by an open circuit (top) and a short circuit (bottom). A pulse reflects perfectly off both these terminations, but the sign of the reflected voltage is opposite in the two cases. Black dots represent electrons, and arrows show the electric field.
The special cases of open circuit and short circuit lines are of particular relevance to stubs. Reflections cause standing waves to be set up on the line. Conversely, standing waves are an indication that reflections are present. There is a relationship between the measures of reflection coefficient and standing wave ratio.
The free end of the stub is either left open-circuit, or short-circuited (as is always the case for waveguides). Neglecting transmission line losses, the input impedance of the stub is purely reactive ; either capacitive or inductive , depending on the electrical length of the stub, and on whether it is open or short circuit.
For example, a short circuit is a fault in which a live wire touches a neutral or ground wire. An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire (phase or neutral) or a blown fuse or circuit breaker.
When the cell is operated at open circuit, = 0 and the voltage across the output terminals is defined as the open-circuit voltage. Assuming the shunt resistance is high enough to neglect the final term of the characteristic equation, the open-circuit voltage V OC is: