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An initial SFRA test is carried out to obtain the signature of the transformer frequency response by injecting various discreet frequencies. This reference is then used for future comparisons. A change in winding position, degradation in the insulation, etc. will result in change in capacitance or inductance thereby affecting the measured curves.
In the power systems analysis field of electrical engineering, a per-unit system is the expression of system quantities as fractions of a defined base unit quantity. . Calculations are simplified because quantities expressed as per-unit do not change when they are referred from one side of a transformer to t
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.
Other advantages of autotransformers include lower leakage reactance, lower losses, lower excitation current, and increased VA rating for a given size and mass. [ 2 ] An example of an application of an autotransformer is one style of traveler's voltage converter , that allows 230-volt devices to be used on 120-volt supply circuits, or the reverse.
The transformer utilization factor (TUF) of a rectifier circuit is defined as the ratio of the DC power available at the load resistor to the AC rating of the secondary coil of a transformer. [ 1 ] [ 2 ]
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A further transient problem is that with a single coil construction and a star switch, the autotransformer acts as a step-up transformer during the <5 microsecond period at contact separation of the Star point switch. With the motor connected to the 80% voltage tap there will be an escalation of the transient by 5:1 ratio.
The service factor is typically in the 1.15-1.4 range, with the figure being lower for higher-power motors. For every hour of operation at the service-factor-adjusted power rating, a motor loses two to three hours of life at nominal power, i.e. its service life is reduced to less than half for continued operation at this level.