Saving energy while safeguarding quality in the long term

With the modernisation of the impregnation system, BENNING is setting the course for the long-term, economical production of windings of the highest quality at the Bocholt (North-Rhine Westphalia, Germany) site

The commissioning of the new, spacious drying oven with regenerative thermal oxidation (RTO) in the electrical machinery (BeM) area successfully achieves the first phase of the “Impregnation Modernisation and Expansion” project. Preparations for the second phase, in which the vacuum impregnation systems will also be replaced during the course of next year, are already in full swing. With these investments, BENNING is securing the energy-efficient and environmentally friendly production of wound equipment such as coils and transformers for the next one or two decades.
It is a clear commitment to Bocholt as a location.

Wound equipment is everywhere. They can be found in medical technology systems, in the automotive sector, in electrical engineering and electronics, in electric motors as well as in energy generation and supply systems.

A finished component is moved out of a drying oven
A finished component is moved out of the drying oven
Power supply systems with open door and bottom with winding goods
Power supply systems above with winding components
DC rotor after impregnation and drying
DC rotor after impregnation and drying
Newly wound stator before impregnation
Newly wound stator before impregnation

In these demanding areas, the components used must meet high technical requirements and withstand high demands. A defect and the associated failure – such as of a hydropower generator – is usually associated with large economic losses for the operator of the plant. Once installed, these components can often only be replaced on site with a great deal of time or not at all.

High voltage and insulation resistance

Therefore, at BENNING, the transformers for stationary power supply systems, traction chargers as well as coils and other components or component groups for electrical machines, are cast with special resins and lacquers under vacuum. This sealing with so-called secondary insulating materials guarantees high mechanical resistance and protection against environmental influences. In addition, maximum high-voltage and insulation protection is achieved.

Three factors are decisive for the quality of the impregnation and the associated service life of the winding; the secondary insulating materials used, the vacuum impregnation and the final drying process.

The respective purpose of the various components to be treated requires an individual composition of the insulating materials to be used. After curing, the precisely coordinated formulations give the impregnated component exactly the desired electrical, mechanical and thermal properties it needs for its application. For example, the rated voltages range from a few volts (< 100 V) to high-voltage coils with 13,000 volts.

Another challenge is the careful impregnation of the components themselves. Because of the complexity of the components with many edges and corners, cavities can quickly form. The air bubbles trapped inside would significantly reduce the high-voltage insulation and possibly even render the component unusable. Therefore, a vacuum is created in the impregnation container, which eliminates even the smallest air pockets and accurately fills all cavities with the impregnation medium.

Newly wound electrical motor after and before impregnation
Newly wound motor (left) after and (right) before impregnation

Robust, durable insulation system

Finally, the drying and curing process takes place in the new chamber oven. In order for the substances present in the formula of the impregnation medium to react with each other as desired, the temperature curve must be finely adjusted during the drying time. For this purpose, individually adjusted temperature curves can be programmed and stored in the control system of the new chamber oven. The result is a robust and durable insulation system of the best quality.

The furnace chamber has an internal dimension of 3 x 3 x 3 m and is loaded with the impregnated windings such as transformers, coils, chokes, motor or generator windings via a movable table – the so-called furnace trolley. With a maximum output of 200 kW, temperatures of up to 180 °C can be generated inside in a controlled manner. Specially programmable temperature-time curves are used for this purpose.

The volatile hydrocarbons (VOC – Volatile Organic Compounds) produced during the curing process are completely converted into harmless components post-combustion in the regenerative thermal oxidation plant (RTO plant).

A finished component is moved out of a drying oven
A finished component is moved out of the drying oven

Efficient energy recovery

Two heat recovery chambers are located below the central combustion chamber, where the thermal oxidation of the pollutants takes place. They are equipped with a heat storage mass that can absorb, store and release energy. This way, the heat from the clean exhaust air is transferred to the raw gas. Thus, by the time it reaches the combustion chamber, it is preheated close to the temperature needed for oxidation. The combustion of the organic components contained in the raw gas, which already takes place autothermally from a concentration of approximately 1.8 g/Nm³, is now sufficient to transform the raw gas into clean gas by means of oxidation.

This reduces the use of the main burner to the start-up phase of the oven. From the combustion chamber, the hot clean gas flows through the heat recovery chambers and leaves the plant as clean exhaust air.

Installation of the drying oven: Delivery and installation of the chimney
Installation of the drying oven: Delivery and installation of the chimney

Quality, sustainability, economic efficiency

This efficient form of heat recovery, combined with the modern oven control, now saves about 70 % of the natural gas used in the BeM compared to the old system. At the same time, these optimised manufacturing methods contribute to a reproducible level of quality that guarantees the longevity of the manufactured windings for electrical machines as well as for the transformers of the company’s stationary power supplies and traction chargers used worldwide.

Cost-effectiveness, quality and a careful approach to our environment go hand in hand here. The project “Watering House Modernisation and Expansion” is another example of a corporate philosophy that intelligently combines the sustainable use of our natural resources with economic action and maximum quality standards.

Further Information

author/contact: Volker Jenneßen
telephone: +49 2871 93 269

Go back