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The transformers are usually rated at 5 kVA, 10 kVA, and 25 kVA. The load densities are usually below 0.5 kVA per kilometer (0.8 kVA per mile) of line. Any single customer's maximum demand will typically be less than 3.5 kVA, but larger loads up to the capacity of the distribution transformer can also be supplied.
Closer to the customer, a distribution transformer steps the primary distribution power down to a low-voltage secondary circuit, usually 120/240 V in the US for residential customers. The power comes to the customer via a service drop and an electricity meter. The final circuit in an urban system may be less than 15 metres (50 ft) but may be ...
Pad-mount transformers are (nearly always) oil-filled units and so must be mounted outdoors only. The core and coils are enclosed in a steel oil-filled tank, with terminals for the transformer accessible in an adjacent lockable wiring cabinet. The wiring cabinet has high and low-voltage wiring compartments.
Pole-mounted transformers may have lugs allowing direct mounting to a pole or may be mounted on cross-arms bolted to the pole. Aerial transformers, larger than around 75 kVA, may be mounted on a platform supported by one or more poles. [13] A three-phase service may use three identical transformers, one per phase.
A typical one-line diagram with annotated power flows. Red boxes represent circuit breakers, grey lines represent three-phase bus and interconnecting conductors, the orange circle represents an electric generator, the green spiral is an inductor, and the three overlapping blue circles represent a double-wound transformer with a tertiary winding.
Parallel operations: All the transformers should have same phase rotation, vector group, tap setting & polarity of the winding. Ground fault Relay: A Dd transformer does not have neutral. To restrict the ground faults in such systems, we may use a zigzag wound transformer to create a neutral along with the ground fault relay.
A wiring diagram for parts of an electric guitar, showing semi-pictorial representation of devices arranged in roughly the same locations they would have in the guitar. An automotive wiring diagram, showing useful information such as crimp connection locations and wire colors. These details may not be so easily found on a more schematic drawing.
A transformer steps up the output of the system's amplifier to the distribution voltage. At the distant loudspeaker locations, a step-down transformer matches the speaker to the rated voltage of the line, so the speaker produces rated nominal output when the line is at nominal voltage.