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However, a transformer may include a tap changer on each winding if there are advantages to do so. For example, in power distribution networks, a large step-down transformer may have an off-load tap changer on the primary winding and an on load automatic tap changer on the secondary winding or windings. The high voltage tap is set to match long ...
The ammeter reading gives the primary equivalent of full load current I L. As the voltage applied for full load current in short circuit test on transformer is quite small compared to the rated primary voltage of the transformer, the iron losses in the transformer can be taken as negligible here.
The ratio of the voltage bases on either side of a transformer is selected to be the same as the ratio of the transformer voltage ratings. With these two rules, a per-unit impedance remains unchanged when referred from one side of a transformer to the other. This allows the ideal transformer to be eliminated from a transformer model.
Real transformer equivalent circuit. One case of voltage regulation is in a transformer. The unideal components of the transformer cause a change in voltage when current flows. Under no load, when no current flows through the secondary coils, V nl is given by the ideal model, where V S = V P *N S /N P.
For example, wall switches intended to control incandescent lamps will have a "T" rating, indicating that they can safely control circuits with the large inrush currents of incandescent lamps. The inrush may be as much as 14 times the steady-state current and may persist for a few milliseconds for smaller lamps up to several seconds for lamps ...
For AC-operated devices (e.g. coaxial cable, loudspeakers), there may even be two power ratings, a maximum (peak) power rating and an average power rating. [ 5 ] [ 6 ] For such devices, the peak power rating usually specifies the low frequency or pulse energy, while the average power rating limits high-frequency operation. [ 5 ]
Distribution transformers typically have ratings less than 200 kVA, [3] although some national standards allow units up to 5000 kVA to be described as distribution transformers. Since distribution transformers are energized 24 hours a day (even when they don't carry any load), reducing iron losses is vital in their design.
The quarter wave transformer is an alternative to a stub; but, whereas a stub is terminated in a short (or open) circuit and the length is chosen so as to produce the required impedance transformation, the λ/4 transformer is in series with the load and its length and characteristic impedance are designed to produce the required impedance ...