High power pulses such as those that occur in short-time tempering or spot welding cause tremendous costs: This is because the power companies calculate the costs on the basis of the maximum power, even if it is needed for only a few seconds. It, therefore, makes sense to supply the power for such applications independently of the mains – for example by means of capacitors that are designed for high power peaks.
IDEA GmbH is testing such a concept in a pilot project. The main role is played by custom capacitor cabinets from Mersen. IDEA develops high-efficiency products and solutions for induction heating applications, such as tempering, soldering and shrinking. “Our expertise also includes induction tempering applications”, explains Andreas Häußler, Managing Director of IDEA GmbH. “Our induction heating systems are in use worldwide for the efficient tempering of diverse workpieces with extreme precision.” The systems of the company based in Baden-Württemberg feature a flexible adaptation and frequency range, to enable optimal design of the custom heating process.
Figure 1: The control cabinets from IDEA are equipped with threaded aluminium electrolytic capacitors of the GM series from FTCAP Photo: Mersen
Saving Energy and Costs with Capacitor Cabinets
To be able to offer customers state-of-the-art technology at all times, IDEA continues to research new processes and methods. Currently the experts are analysing whether special capacitor cabinets can save energy and reduce costs in short-time tempering applications. “Induction heating and welding systems often require high power for a very short time, in the range of milliseconds”, explains Andreas Häußler. This is especially the case in spot-welding systems for automotive construction. But applications with requirements for precise contours in the tempering of gear wheels also require a high power pulse for a short time in order to quickly heat the surfaces of the components before they are quenched. “In the past, this process was implemented without capacitors, which means the high power pulses are drawn from the regular mains network.”
However, that puts a load on the mains and results in substantial energy costs, which are calculated on the basis of the maximum power draw. “Even if the application requires heat for only one second at 1 MW, you have to pay the power company the flat rate for the maximum power of 1 MW”, explains Andreas Häußler. “It then makes no difference how long the breaks are between the heating phases.” The mains elements must also be designed for high power outputs, which also causes additional costs. The problem could be alleviated by capacitor banks used as energy buffers between the mains connection and the application. “By buffering with capacitors and supplying a continuous charge of 100 kW, one has to pay only for the reduced power”, explains Andreas Häußler. “The upstream elements can likewise be designed for lower power to reduce costs.” Systems such as these, however, do not yet exist – although IDEA will soon start a pilot project to analyse the potentials.
High Standards for Capacitors
The first step was to procure suitable capacitors. Of course, the experts at IDEA again placed their confidence in Mersen, a time-proven supplier with which the company has a long-standing business relationship. The standards were high: IDEA required capacitor cabinets that provide a very high capacity in a very small design. “The systems must allow several million charge and discharge cycles at ambient temperatures up to 55 °C, without the occurrence of defects or significant capacity losses”, explains Andreas Häußler. “Maximum efficiency also requires very low internal impedance and low self-discharge.” In terms of performance, the buffers must be capable of a power output of several hundred kilowatts for about one second. The process design then requires a break of several seconds.
Figure 2: Mersen developed a concept for IDEA in which numerous capacitors are installed in each cabinet; Photo: Mersen
Mersen developed a concept for IDEA in which numerous capacitors are installed in each cabinet. “For the pilot project we will initially deliver two cabinets, which are being built and equipped at our own facilities”, says André Tausche, Managing Director of FTCAP (part of the Mersen Group). “In addition to the capacitors, we are also supplying the required telescoping rails, cross braces and symmetrical resistors. We also provide professional installation of the rails and capacitors on the panels.” The entire production process for the assembly is carried out by IDEA.
Figure 3: IDEA GmbH develops high-efficiency products and solutions for induction heating applications, such as tempering, soldering and shrinking; Photo: IDEA GmbH
Figure 4: Applications with requirements for precise contours in the tempering of gear wheels require a high power pulse for a short time in order to quickly heat the surfaces of the components Photo: IDEA GmbH
High Capacities and a Long Life
The control cabinets from IDEA are equipped with aluminum electrolytic capacitors with a threaded connection of the GM series from FTCAP. Even at high operating temperatures of up to 85 °C, each of the capacitors has a very long life of about 8,000 hours. In addition, these aluminum electrolytic capacitors, in which all internal contacts are welded, can be used in a broad voltage range from 16 V – 450 V, and they also feature very low inductance.
Capacitors with a threaded connection are generally suitable for all applications requiring very close integration of the components with their environment”, explains André Tausche. “That is the case not only in the current project but also in medical and railway technology, for example.” The GMX Long Life series is designed for a long life, which makes it ideal for use in medical technology. The GW series was developed for the even harsher conditions of railway technology. These aluminum electrolytic capacitors are insensitive to high ripple currents and also feature very low inductance. FTCAP developed the GF series especially for environments with stringent safety requirements. These aluminum electrolytic capacitors consist of a self-extinguishing electrolyte and are used for example in industrial welding machines.
Figure 5: Currently IDEA is analyzing whether special capacitor cabinets can save energy and reduce costs in short-time tempering applications; Photo: IDEA GmbH
Andreas Häußler is satisfied with the choice of capacitors: “The very high-volume power density, long life and low inductance of GM series capacitors from FTCAP make them ideal for our pilot project”, emphasizes the managing director of IDEA. The first tests of the two capacitor cabinets are scheduled to start soon. If the concept proves to be viable, Mersen will be involved in the long term: “Mersen is an established, reliable and flexible supplier of IDEA GmbH. We are pleased to have a strong partner at our side who can also implement small-series custom solutions that are optimized for the particular application”, says Andreas Häußler in conclusion.
This article originally appeared in Bodo’s Power Systems magazine.