SU1787316A3 - Tube electric heater and method of its manufacture - Google Patents

Description

The invention relates to electrothermal, in particular the production of tubular electric heaters for domestic and industrial heating devices.

Known electric heater containing a tubular base of natural mica, a heating coil and an external mica cylinder. In its manufacture, the wire wound on the mica cylinder is brought to red heat, sprinkled with boric acid, allowed to melt and put on the outer mica cylinder.

Such an electric heater has insufficient mechanical and electric strength, since the fused boric acid kit of diameter 2 is made of mica-containing material, the smaller of which is wound with a heating coil, and a sleeve of a larger diameter is worn. One of the sleeves or both are made combined of mica-containing materials with different values of the dielectric constant at the operating temperature of the heater, the ratio of dielectric constant is not less

1.5, with layers with a higher dielectric constant located directly in contact with the heating coil and make up 25-50% of the thickness of the sleeve. As mica material with a high dielectric constant, mica paper impregnated with an aqueous solution of a phosphate binder can be used, with a lower dielectric constant of mica paper impregnated with an organosilicon binder. 2 sec P. f-ly, 4 ill.

lot is very fragile and hygroscopic. Abundantly absorbing moisture from atmospheric air, the heater loses its electrical insulation properties. The outer mica cylinder during operation can be easily shifted, because it is. firstly, it is not mechanically fixed, and secondly, the brittle fused boric acid breaks out, which also affects the electrical insulation of the heater. In addition, with direct contact of a hot conductor with a mica cylinder, mica swells and mica base is destroyed with a loss of electrical strength. And finally, the use of natural mica for the manufacture of cylinders, except

-1787316AZ high cost, limits the minimum diameter of the cylinders - ιϊριτ decreasing the diameter of the mica cracks and breaks. The closest in technical essence and the proposed result is 5 electric heater made of. two electrical insulating mica sleeves of various diameters. A heating spiral, then mica paper, is wound on a sleeve of smaller diameter. 1 (impregnated with a creme with an organic binder, the assembly is run on a micalex plate, mounted on a larger diameter and heat treated at a temperature of degradation of the silicone binder.

In this case, a monolithic, mechanical, durable electric heater is obtained, however, its electric strength at operating temperatures of 500-600 ° C is limited to 2 (per. Reliable value of the test voltage at the indicated temperatures is 1250 V, t, e. The heater corresponds to the zero electrical safety class. This is caused by the destruction of the organosilicon binder at the indicated temperatures and the formation of air gaps between the mica flakes in the insulation material, which drastically reduce the dielectric strength by . Revatelya 3I Tsely invention - increase the electric strength of the electric heater.

This goal is achieved by the fact that one of the sleeves or both, depending on the direction of heat removal fc electrically heating-3! .bodies made of Y mica-containing materials combined with different values of dielectric constant at the operating temperature of the heater. 4'

The ratio of the dielectric permittivity '· <of the material capacities is at least 1.5, *' and moreover, from mica material with a higher dielectric constant, they are facing the zone of direct contact of the sleeve with 4: a heating spiral and make up 25.Υ 50% of the entire thickness of the sleeve. As mica material with great value. dielectric constant at operating temperature, mica paper was used, impregnated with an aqueous solution of a phosphate binder, and mica paper impregnated with an organosilicon binder was used as a mica material with a lower dielectric constant. 5

The use of a combined sleeve allows increasing the electric strength of the heater due to the fact that in the proposed design there is a redistribution of the applied working or test voltage in the insulating materials depending on the values of the dielectric constant of the materials at a working temperature of 5 heater - gradation of the electric FIELD. ;

When a material with a higher dielectric constant is located directly in the zone of contact with the heating coil, it accounts for a lower applied voltage, because in the case of the sequential arrangement of two electrical insulating materials with different dielectric constants, the voltages are redistributed inversely with the dielectric constants.

A material with a lower value of the dielectric constant is redistributed20 a large value of the applied voltage. In this case, it is necessary to take into account the influence factor of various temperatures on the used insulating materials, i.e., located directly in the zone of contact with heating. With a natural spiral material, higher temperatures act than on the material from which the layers are made, which are remote from the heating spiral and are in 30 contact with surfaces that produce heat removal. A ratio of the dielectric constants of mica-containing materials of -1.5 is sufficient before normal gradation of the field, with lower ratios of 35 approaching 1.0, the insulation operation mode becomes close to the operation mode of uniform insulation.

In addition, it is necessary to increase the thickness of the insulation, which entails an increase in thermal resistance and a deterioration in the resistivity.

Based on this, it was suggested that Slyudoba45 be used as a material with a high dielectric constant, impregnated with an aqueous solution of a phosphate binder, having a dielectric at a working temperature of 700-800 ° C. permeability of the order of 12, and dielectric strength in an inhomogeneous 50 electric field - 5 kV / mm. As a material with a lower dielectric constant, use mica paper impregnated with an organosilicon binder. It has a working temperature of 55 to 600 ° С, the dielectric constant at a given temperature is 4, and the electric strength in an inhomogeneous field reaches

7.5 kV / mm. The thickness of the sleeve and the thickness of the layers ____ of various materials is determined from the condition of minimum resistance to heat flux and the breakdown voltage of the corresponding mica-containing materials in an inhomogeneous electric field at operating temperatures of the electric heater. At the maximum allowable working temperatures on a resistive material, the thickness of the layer of material with a higher dielectric constant is 25-50% of the entire thickness of the sleeve. At a thickness of less than 25%, a layer of mica-containing material with a higher dielectric constant is insufficient to lower the temperature to 600 ° C and ensure normal operating conditions for a layer with a lower dielectric constant, which leads to a decrease in its electric strength, with a thickness of more than 50% of the entire sleeve, the layer thickness mica-containing material impregnated with an organosilicon binder will be insufficient in its electric strength, since it is this layer that provides the electric strength of all electric heater. ·

In FIG. 1 is a perspective view of a tubular electric heater: FIG. 2 fragment of an electric heater with a combined sleeve of smaller diameter: in FIG. 3 - a fragment of an electric heater with a combined sleeve of a larger diameter; in FIG. 4 - a fragment of an electric heater with two combined sleeves.

The electric heater consists of a sleeve of a smaller diameter 1, a heating coil 2 wound around it, and a sleeve of a larger diameter 3, worn over Na15

The use of one of the sleeves or both combined allowed us to create a new high-voltage electric heater based on mica-containing materials, which has no analogues.

Claims (2)

Claim 1. A tubular electric heater containing two sleeves of different diameters made of mica-mica (its material, on a smaller one which is wound with a heating spiral and put on a sleeve of a larger diameter, Otl 4 and Yuschiy with the fact that, in order to increase the electric strength insulation of the heater, at least one of the sleeves is made of two-layer mica materials with different dielectric constants at the operating temperatures of the electric heater in each layer, the ratio of the dielectric constant of the layers is not less than e 1,5. moreover, the layer from SluYoma'terial with a higher dielectric constant adjoins the heating coil, and the thickness of this layer is 25-50% of the entire thickness of the sleeve. 2. An electric heater according to Claim 1, wherein the layer with a high dielectric constant at an operating temperature of the electric heater is made of mica paper impregnated with an aqueous solution of a phosphate binder, and the layer with a lower dielectric constant is made of mica paper impregnated organosilicon 1787316 Editor Compiled by T. Nikulin Tehred M. Morgenthal Corrector N. Gunko Order 275 Circulation Subscription VNIIIPI of the State Committee for Inventions and Discoveries under the State Committee for Science and Technology of the USSR 113035, Moscow, Zh-35, Raushskaya nab., 4/5 Production and Publishing Plant Patent, Uzhgorod, Gagarin St. 101