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The neutral current can be determined by adding the three phase currents together as complex numbers and then converting from rectangular to polar co-ordinates. If the three-phase root mean square (RMS) currents are I L 1 {\displaystyle I_{L1}} , I L 2 {\displaystyle I_{L2}} , and I L 3 {\displaystyle I_{L3}} , the neutral RMS current is:
A three-phase motor is more compact and less costly than a single-phase motor of the same voltage class and rating, and single-phase AC motors above 10 hp (7.5 kW) are uncommon. Three-phase motors also vibrate less and hence last longer than single-phase motors of the same power used under the same conditions. [26]
The first three-phase alternating current using high voltage took place in 1891 during the international electricity exhibition in Frankfurt. A 15 kV transmission line, approximately 175 km long, connected Lauffen on the Neckar and Frankfurt. [10] [19] Transmission voltages increased throughout the 20th century.
The power factor is 1.0 when the voltage and current are in phase. It is zero when the current leads or lags the voltage by 90 degrees. When the voltage and current are 180 degrees out of phase, the power factor is negative one, and the load is feeding energy into the source (an example would be a home with solar cells on the roof that feed ...
Three-phase systems can be connected to give various combinations of voltage, suitable for use by different classes of equipment. Where both single-phase and three-phase loads are served by an electrical system, the system may be labelled with both voltages such as 120/208 or 230/400 V, to show the line-to-neutral voltage and the line-to-line ...
In 1895, after a protracted decision-making process, alternating current was chosen as the transmission standard with Westinghouse building the Adams No. 1 generating station at Niagara Falls and General Electric building the three-phase alternating current power system to supply Buffalo at 11 kV. [9]
Figure 2 shows the top and bottom views of an air-cooled 10 kW-Vienna Rectifier (400 kHz PWM), with sinusoidal input current s and controlled output voltage. Dimensions are 250mm x 120mm x 40mm, resulting in a power density of 8.5 kW/dm 3. The total weight of the converter is 2.1 kg [10]
With increasing power output, three-phase motors have preferable characteristics to single-phase motors; the latter not being available in sizes over 15 hp (11 kW) and, though available, rarely seen larger than 5 hp (3.7 kW). (Three-phase motors have higher efficiency, reduced complexity, with regards to starting, and three-phase power is ...