Roman Rygal

Apparent core losses and core losses in five-limb amorphous transformer of 160 kVA

Significant modifications of the shape of magnetic flux in columns and yokes were observed in the magnetic circuit of four amorphous cores used in a 3-phase transformer. The magnetic losses measured experimentally were significantly higher than the ones calculated theoretically. The values quoted in this paper were obtained in our study, and they are indicative of the need of taking them into consideration when designing 5-limb amorphous distribution transformers.

An improved method/setup for extended testing after the Cigre, Method II

The authors describe an improved version of the Cigre Method II test techinque used for testing the resistance of insulating materials to partial discharges (PDs). The method was extended to continuous PD measurements and pulse analyses. It was sound that parameters such as selective fuse protection of the different test objects, and the sample production and preparation, among others, were of the utmost importance for the end results of this test. Results of using the system on epoxy with and without fillers are presented. Based on these results, the critical points of the method are discussed. The application of the system showed typical behavior of the discharges and lifetimes that was strongly dependent on the filler type.<<ETX>>

Large DC Electromagnet for Semi-Industrial Thermomagnetic Processing of Nanocrystalline Ribbon

A large dc electromagnet with a 200 mm long air gap was designed, constructed, and tested. Analytical calculations provided the first approximation of required parameters. The design was refined with the aid of finite element modeling. Thermomagnetic processing required nominal flux density level to be 0.35 T. It was validated on a prototype that the average flux density in the air gap exceeded this value. The magnetizing coils were designed to be cooled by natural air convection. Despite a large size (~1900 kg), the electromagnet was designed to consume less than 2.5 kW and could be energized from a single-phase mains socket.

Properties of Fe-based nanocrystalline magnetic powder cores (MPC) and structure of particle size distribution (PSD)

Abstract This paper discusses the influence of the Particle Size Distribution (PSD) of the nanocrystalline Fe-based granular-soft-magnetic material on the final magnetic properties of a Magnetic Powder Core (MPC). Here we show how PSD impacts the final magnetic properties. Mixing fine and coarse particles, with a dominance of coarse particles, significantly influences the magnetic permeability increase of the core. Better magnetic features are noted for MPCs constructed with certain mass ratio of fine and coarse particles due to improvement in the magnetic path in the cores. This allows to offer new induction components to industry.

Addressing an EMC Weakness Due to Strong Static Magnetic Fields

Strong stationary magnetic field from a permanent magnet, or strong electromagnetic field from many different sources, when used in a wrong way, can change a proper behavior in already optimized technical equipment. For example, many electronic electrical energy meters do not count correctly the consumption of electrical energy or low-voltage current transformers do not indicate proper level of output signal. This is the evidence of EM Compatibility lack. To prevent described situation from happen some actions have to be taken. The paper outlines the problem and proposes possible solution to the phenomenon of illegal using of the described EMC weakness.