What is an electrical insulating varnish and why use it?

All paints and varnishes with electrical insulating qualities can be divided into the following groups: impregnating, coating, gluing. For example, electric insulating varnish ML 92, No. 318 and a number of others are used more as a protective impregnation. In addition, ML 92 and 318 are used to process the windings of electrical machines, apparatus, transformers, individual electrical insulating parts.

Content:

• Destination
• Characteristics of varnish ML 92
• Composition and technical characteristics of varnish 318
• Acrylic varnish with insulating properties

Destination

1. Impregnating. They are used as a connecting means of winding turns among themselves, including to reduce porosity in the insulation of windings. The solution, penetrating into the pores, fills the space, thereby giving the elements water-repellent properties. Increases electrical insulation strength, improves electrical conductivity.
2. Coverslips. They are used as an additional protective coating on already impregnated moisture-resistant or oil-resistant surfaces. Solutions of this nature are still used to insulate sheets of electrical steel in magnetic cores.
3. Adhesive. From the name of the group, the main purpose of the substances becomes clear - gluing together individual electrical insulating elements, for example, mica leaves, ceramics, plastics, and so on. One of the important characteristics is the high adhesive properties of the solution.

Despite such a strict distinction between groups, almost all of these solutions can be used to perform two tasks at once, for example, impregnation and coating.

The classification of electrical insulating varnishes includes the distribution not only by purpose, but also by other parameters:

• by the method of drying: cold (in vivo) and hot (under the influence of high temperatures - more than 100 degrees Celsius);
• based: resin, oil, oil-bitumen, etherocellulose.

Characteristics of varnish ML 92

ML 92 with electrical insulating properties is a liquid mixture of glyptal varnish with the addition of melamine-formaldehyde resin. Organic solvents act as a diluent. Typically, the solution is sold ready to use. But to reduce the viscosity of the substance, dilution with toluene, xylene, or a mixture of these substances with white spirit is allowed.

After polymerization, a shiny, brownish protective film is formed on the treated surface. Estimated consumption of the substance is 40-50 g per square meter. The polymerization time of single-layer varnishing is 60 minutes under conditions of high temperature conditions + 105-110. With multi-layer impregnation under the same drying conditions (or 10 degrees higher), curing will occur in about 16 hours.

Important technical characteristics of ML 92 are indicators of electric strength and specific volumetric electrical resistivity of the coating:

1. Electric strength, MV / m:

• at + 18-22 ° С - from 70;
• at + 128-132 ° С - from 40;
• after getting wet during the day at + 18-22 ° С - from 30;

2. Volume resistivity:

• at + 18-22 ° С - from 1.E + 12 Ohm. * m;
• at + 128-132 ° С - from 1.E + 9 Ohm. * m;
• after getting wet during the day at + 18-22 ° С - from 5.E + 10 Ohm. * m.

Due to the fact that volatile chemicals are present in the solution, you should adhere to the rules for working with the product and observe individual safety measures. Another precaution is the elementary fire safety rules.

Composition and technical characteristics of varnish 318

Oil-bitumen varnish 318 forms a black protective film on the surface. It is used for impregnation in the repair of low-voltage electrical machines. Contains organic solvents. It is diluted with white spirit and solvent naphtha.

The recommended drying mode is oven (hot) at a temperature of +105 degrees Celsius.

Of the obvious advantages of oil-bitumen varnish 318 with electrical insulation properties, it should be noted:

• increased moisture resistance;
• class A heat resistance

However, varnish 318 is weakly resistant to the influence of technical (transformer) oils, and is capable of dissolution.

Acrylic varnish with insulating properties

If you are looking for a substance with high dielectric characteristics, you can try acrylic insulating varnish. It is also used for protection against corrosion processes and atmospheric phenomena of the windings of motors and transformers, as well as for printed circuit boards.

Dries pretty fast. It forms a transparent protective film, strong enough and resistant to various influences. Of the undoubted advantages of the solution, we highlight:

• moisture resistance;
• dirt resistance;
• protection against oxidative reactions;
• chemical inertness;
• high dielectric abilities;
• wide range of operating temperature - from -70 ° С to + 100 ° С.

Electrical insulating varnishes and other similar means are needed in order to safely and efficiently use electrical equipment of various configurations.

Especially if such devices operate in automatic mode and perform important technological functions (in production, in everyday life).