A.A. Korobtsov, post-graduate;
A.P. Leonov, Cand. Sc. (Engineering), Associate Professor of Electromechanical Systems and Materials Department;
Yu.P. Pokholkov, Dr. Sc. (Engineering), Professor, Head of Organization and Technology of Higher Professional Education Department;
E.Yu. Soldatenko, graduate student; Tomsk Polytechnical University;
I.A. Kochetkov, Chief Technologist, ZAO “Sibkabel”
Use of enameled wires in windings of frequency-controlled induction motors
When frequency method is used for stepless control of electric drives based on induction motors with a short-circuited rotor the stator insulation experiences overvoltages that significantly exceed the supply voltage value. This causes corona discharges leading to fast ageing of winding wires.
Tests of various type enameled wires were carried out under the exposure to high voltage causing surface discharges in order to determine the ability of the winding wire enamel insulation to withstand long-term operation under frequency control conditions. It was established that of all tested wires the ПЭТД 2-К-180 wire had the highest level of corona resistance.
Enameled wires, ageing, winding wire, frequency control
A.V. Petrov, Cand. Sc. (Engineering), Associate Professor of Electroinsulating and Cable Technology Department, Tomsk Polytechnical University
Method for the estimation of physical and chemical properties of varnishes used for wire enameling
This is the conclusive article in the “Enameled wire production technology” series of articles. It is devoted to the study of properties of enamel varnishes used in the production of winding wires with enamel insulation. The study was based on a thermogravimetric analysis.
A procedure is offered for the determination of dissolvent evaporation time, granularity and degree of enamel destruction when calculating the wire enameling process parameters.
It is shown that the thermogravimetric analysis results for varnishes of different batches help to reveal the specific temperature conditions of the enameling process and the maximum allowed temperature of wire heating in order to achieve the required enamel granularity.
Wire enameling, enamel varnish, enamel insulation, winding wire
E.O. Avtsynova, Student of Physics and Technology of Electrical Materials and Components Department, MPEI
V.A. Govorov, Cand. Sc. (Chemistry), Deputy Director of the Research Laboratory of REC “Nanotechnologies”, Associate Professor of Physics and Technology of Electrical Materials and Components Department, MPEI;
E.A. Maskaev, Student of Physics and Technology of Electrical Materials and Components Department, MPEI
Investigation of montmorillonite dispersion mixture of phthalic anhydride
The authors describe a method for preparing a dispersion by way of mechanical grinding of montmorillonite (MMT) in an organic matrix (FA) using a bead mill in order to obtain a colloidal solution of montmorillonite as a component of the formulation for the insulating material. The stabilization of the dispersion was carried out with the help of special surface-active agents. In the course of the grinding process the particle size distribution was defined and the dispersion viscosity was studied. The study of the particle distribution was performed by the dynamic light scattering method. The viscosity of samples was measured using a rotational rheometer with variable shear stress and shear rate.
Based on the obtained data the conclusions were drawn about the dynamics of the grinding process and the stability of the system. After milling the stability of the dispersion was monitored over several days. The experiment resulted in the formulation of the insulating varnish component comprising a concentrated dispersion of montmorillonite that was stable over time and could be introduced into the formulation after being diluted with pure solvent.
Montmorillonite dispersion , phthalic anhydride, dispersoid solution, organic matrix