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For example, a 24 VCT transformer will measure 24 VAC across the outer two taps (winding as a whole), and 12 VAC from each outer tap to the center-tap (half winding). These two 12 VAC supplies are 180 degrees out of phase with each other, measured with respect to the tap, thus making it easy to derive positive and negative 12 volt DC power ...
location and specifications for distributed control devices such as tap-changing transformers, switched shunt compensation, static Var compensators, flexible AC transmission systems, etc., location and specifications for protection devices such as relays and load shedding, and
A transformer supplying a three-wire distribution system has a single-phase input (primary) winding. The output (secondary) winding has a center tap connected to a grounded neutral. As shown in Fig. 1, either end to center has half the voltage of end-to-end. Fig. 2 illustrates the phasor diagram
Center-tapped delta transformer Center-tapped delta transformer voltages. High-leg delta service is supplied in one of two ways. One is by a three-phase transformer (or three single-phase transformers), having four wires coming out of the secondary, the three phases, plus a neutral connected as a center-tap on one of the windings.
Assuming the desired voltage is the same on the two and three phase sides, the Scott-T transformer connection (shown right) consists of a centre-tapped 1:1 ratio main transformer, T1, and a √ 3 /2(≈86.6%) ratio teaser transformer, T2. The centre-tapped side of T1 is connected between two of the phases on the three-phase side.
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 ...
If the secondary is a delta winding, the ground may be connected to a center tap on one winding (high leg delta) or one phase may be grounded (corner grounded delta). A special purpose polyphase transformer is the zigzag transformer. There are many possible configurations that may involve more or fewer than six windings and various tap connections.
Both linear spacing and power-of-two-style Vernier spacing can be employed in establishing the tap positions, e.g., a four-tap transformer can provide taps at 0.25, 0.5, 0.75, 1.0 (linear) or 0.0625, 0.125, 0.25, and 0.5 (Vernier). (The limitations of the Vernier—in this case, that the maximum obtainable amplitude is 0.9375—are less ...