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Transformers
Published in Jacek F. Gieras, Electrical Machines, 2016
A Scott transformer (Fig. 2.34) is a special electromagnetic device used to convert a three-phase system to a two-phase system, or vice-versa. It consists of two single-phase transformers. The first single-phase transformer is called the main transformer. It has a center-tapped primary winding connected to the three-phase circuit with the secondary winding connected to the two-phase circuit. The ends of the center-tapped main primary winding are connected to two of the phases of the three-phase circuit. The second single-phase transformer is called the teaser transformer. It has one end of its primary winding connected to the third phase of the three-phase circuit and the other end connected to the center tap of the primary winding of the main. The Scott connection requires no primary neutral connection, so zero-sequence currents are blocked. The secondary windings of both the main and teaser transformers are connected to the two-phase circuit.
Review of Control Topologies for Shunt Active Filters
Published in L. Ashok Kumar, S. Albert Alexander, Computational Paradigm Techniques for Enhancing Electric Power Quality, 2018
L. Ashok Kumar, S. Albert Alexander
While considering the kV A rating, T-connected and Scott transformers are lower compared to other schemes and, on the basis of comparing the economic aspect, Scott transformer with ZSBR is preferred since it requires only two single-phase transformers. The T–T-connected transformer investigated introduced values of negative- and zero-sequence currents of less than 1.5%. The level of voltage unbalance (dependent upon the amount of negative- and zero-sequence current flowing in the circuit) introduced by the T–T-connected transformer is quite acceptable in a distribution system, since the winding-to-winding impedances of the T–T-connected transformer are a small percentage of the total load impedance(s). The T–T-connected transformer, however, cannot be used as a high-voltage power transmission device since the higher per unit winding-to-winding impedances normally associated with this type of transformer would cause a prohibitive increase in the voltage unbalance. It can be concluded that The negative- and zero-sequence currents introduced by the T–T-connected transformers may be found by utilizing the interconnected positive-, negative-, and zero-sequence impedance circuits of the transformer.The T–T-connected transformer, when used as a distribution transformer, introduces negligible negative- and zero-sequence voltages and therefore maintains an acceptable three-phase voltage balance under full load conditions. This is due primarily to the low per unit winding-to-winding impedances inherent in the constituent single-phase transformers.
Signal Converter with Three-Phase and Quadrature Outputs for Driving Synchros and Resolvers
Published in IETE Journal of Research, 2022
Darko Vyroubal, Vedran Vyroubal, Damjan Belavić, Zoran Halić
The block diagram depicting this process according to Equation (1) is in Figure 2. The reference signal (Ref) from the outside signal generator is used as the in-phase (I) and phase A signal, as well as, the input signal for I/Q converter where the quadrature signal (Q) is generated. The phase B and phase C signals are derived from A and Q signals in the electronic implementation of the Scott-T transformer circuit [3,4]. Practical realization of the block diagram in Figure 2 was done both with digital [5,6] and analog circuits [7,8]. Analog solution to the problem is adopted in this paper, primarily because of versatility, simplicity and cost. Analog implementation of the Scott-T transformer according to Figure 2 is straightforward, but care must be taken to preserve precision when realizing the 0.866, i.e. /2 gain (it will be addressed later).