Transformer Based Solutions to Power Quality Problems

In this paper we propose transformer-based solutions to several power quality problems. Elsewhere we have shown how to solve the acoustical noise emission problems. In this paper we introduce toroidal transformers with reduced inrush currents, transformers with reduced electromagnetic emissions, and other transformers useful to reduce the transfer of harmonics. With the low-inrush transformers we are able of eliminating (or reducing) voltage sags and nuisance service interruptions caused by false operation of breakers and fuses. The low-stray emissions transformers are used for reducing the electromagnetic interference (EMI) caused by stray fields emitted from the transformer. Electromagnetic noise reduction transformers (NRT) are used reduce the harmonic pollution problem. Because of their construction tape-wound toroidal transformers are more efficient and produce less acoustical and electromagnetic noise than standard E-I transformers. Therefore, properly designed and built toroidal transformers are smaller and/or work cooler. The power density (per volume or weight) is larger. The sole disadvantage could be that standard toroidal transformer designs produce larger inrush currents. We have solved the inrush problem right from the transformer design without resorting to external inrush limiting circuits. Therefore we increase the reliability of the overall system while simultaneously reducing cost. We have also reduced the electromagnetic field emissions even below the already reduced fields emitted by standard toroidal transformers. In addition, we have invented a transformer with a narrow frequency bandwidth to limit the transfer of harmonics from primary to secondary or viceversa.