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Background: Questions about the DES

1 . Are not brake resistor and energy buffer philosophically contradictory?

We pursue the philosophy of rationally managing produced braking energy. Which solution is optimum for this is decided by the application case. We also definitely advise our customers in the direction of mains feedback if the application allows this as practical. However, we are the specialists for products which deal with the braking energy independently of the mains. Only resistors and electrical storage remain in the electrical equipment. Or in short: The energy buffer, as we call it, is a practical supplement to our reliable brake resistors.


2. Are we operating in the same market segment with the Dynamic Energy Storage (DES) as with the brake resistor?

To date, we have been providing reliable brake resistors for the smaller power range. Using our modular system, we achieve continuous outputs beyond seven kilowatts. We can absorb a lot of this for short pulses. If the resistor has sufficient time to recover thermally, the product range is sufficient for a large part of mechanical engineering. We can cover some of these applications with our Dynamic Energy Storage. Thus, we are operating in the same market segment, however only in a small section of it. Our DES is ideal for short cycles and frequent braking.


3. Energy buffers are considered as negligible solutions by many large manufacturers. Why are we taking the risk?

This is why. As already mentioned, the DES concerns a small market segment which is not lucrative enough for large manufacturers. We are used to such small market segments and can adapt to it. And we also assume that some of the major players of the sector will use us. We also provide the customisation of our product for small quantities. In this way, an economically practical production can arise.


4. Why has our energy storage earned the "dynamic" attribute?

Because it adapts itself to the converter. And in fact in two ways. First, it adapts itself to the voltage level of the intermediate circuit. It knows due to the first braking at which voltage it must absorb energy. And secondly, it adapts itself to the output requirement. It adapts itself to braking with high starting output differently to braking with a smaller starting output.  The frequency of the cycles of energy absorption and output can also be designated as dynamic.


5. What can this box full of secrets do?

The DES is not so mysterious. We therefore only call it "black box" because the user does not need to make any settings. It does not require anything more than a brake resistor. The DES simply functions without configuration effort with every converter in the connection voltage range of 400 to 460 Volts and a direct intermediate circuit connection. The device then performs the storage and output again for every drive cycle of the kinetic energy converted into electrical energy, i.e. the braking energy. Independently of the mains power.


6. Power saving and emergency power generator: Who can and should use braking energy without mains power?

For whose application it is worthwhile or would like to save the electrical energy whatever it costs. Seriously. The DES is one of several possibilities to manage braking energy independently of mains power. The application must be examined precisely and calculated in order to establish whether the use is financially worthwhile. There are individual cases; however the majority retain brake resistors. And our DES is certainly also an alternative for whoever has or fears problems with an unstable mains power supply.


7. Switch cabinet or directly on the machine: Where is the place for the dynamic energy storage?

Currently, still in the switch cabinet because the current version has protection class IP 20. We provide reliable brake resistors with protection class IP 65 for decentralised use. The development of the DES will certainly not remain static.


8. A few months ago, we extended our "factory" in Ubstadt-Weiher. There is the question: "Have you developed energy buffers with your team during the conversion work?"

Yes, of course! We could not shut down our business for months. Despite all the difficulties associated with construction work during running operation, all employees did their part and we were able to perform the running customer projects as well as the development projects.


9. How did we actually have the idea of the dynamic energy storage?

We had already been thinking for a long time about a possibility which can replace the brake resistor and store energy in certain cases and thereby function independently of mains power. Not much other than the energy buffer remains in the electrical equipment. It was and is important that it had to be a universally usable product which is just as easy to handle as a brake resistor. The DES result is now finally ready for series production.


10. Short: How exactly does DES function?

The energy storage itself is a large electrolytic capacitor which is connected to the intermediate circuit of the converter via a buck/boost converter. All state of the art including the self adjustment. The DES establishes when the braking case occurs and it has to take energy from the intermediate circuit as well as recognise when it has to feed energy back into the intermediate circuit. A small brake resistor is also still installed which can also trap unexpected peaks. All performed in robust technology and designed for the service life of machines.


11. The principle is not new; why are we implementing it now?

On the one hand because it is the right time. Energy efficiency is THE topic and we want to show that we are also making thoughts beyond our established brake resistor product. And on the other hand, because we have now succeeded in creating a universal storage unit which is suitable for every converter with 400 to 460 Volts connection voltage without configuration effort. And that is really new: The dynamism of adapting to the situation with respect to voltage and output.


12. When will we have sold the first DES?

We will arouse initial interest with the presentation at SPS/IPC/DRIVES. As with the founding of our company and introduction of our reliable brake resistors at the end of the 1990s, it will now also take some time until we have achieved initial successes with the DES. However, we are optimistic and have patience. We believe that machine constructors are being increasingly pressed by their customers to design their machines to be energy-efficient and that it is very important not to simultaneously overload the mains power. We are now providing a convenient solution for this. And we are also thinking of drive technology companies who sometimes have an enquiry to satisfy but shy away from the costs for in-house development. As with our resistors, we are also prepared with the DES for the customisation of the product


13. Why should the user use DES? How is DES cost-effective? And how quickly can it amortise?

It is worthwhile if braking energy should be made usable independent of mains power. The advantages of the DES become noticeable mainly for short cycles and frequent start/stop actions or direction changes. The amortisation time is of course dependent on the application and must be calculated individually. The DES can save several thousand kilowatt hours per year in three-shift operation and short cycles. The possibility of energy saving itself is reason enough for the use for many customers.


14. How long can a capacitor hold a charge of energy?

In principle, the storage and retrieval of energy with the DES is intended for applications with short and quick work cycles. For this mode of operation, the braking energy will definitely be stored in full and can be retrieved without significant losses. In case of excessively long pauses between work cycles, it must be noted that the standby losses of the converter discharge the DES to a residual voltage that depends on duration of the interruption. The discharge period is extended if the DES is turned off by a fault.


15. Does an option exist to force a discharge for maintenance purposes?

Yes, a discharge contact can be used to drain the capacitor of any remaining charge via an internal resistor. A monitoring LED on the DES indicates the presence of a charge. Any work shall only be carried out when this LED has been turned off completely.


16. What is the maximum length for supply lines to the DES?

The supply lines should be as short as possible since they act as an inductance. The shorter, the better! Positive and negative cables from the intermediate circuit to the DES should be twisted close together. In this case, a length of up to 1m is acceptable. Longer cables may need additional measures. This could also require screening.


17. Is the DES protected against reverse polarity connections?

We have provided an operating and installation manual for technicians that clearly shows how the DES must be connected. In addition, the connections on the DES are clearly marked. A fuse protects the DES if the connections should be confused in spite of these measures. In the worst case, it may have to be replaced or exchanged by KOCH.

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