Don’t be a victim of mains failures again…

Published:  05 April, 2016

If machines and systems come to a sudden stop because of mains failures, the consequences are expensive and time consuming. These effects can be limited by implementing different bridging concepts of mains failures. PWE spoke to Manuel Senk, product manager, Interface & Mico at Murrelektronik GmbH in Oppenweiler.

Electrical engineers and machine designers usually choose modern power supply units with a standard mains bridging time of more than 20 ms. Within this period, the power supply delivers the output current from the power contained in the internal storage. This is sufficient to bridge short mains fluctuations and power failures.

But often, the failures are longer, and can reach up to 180 ms easily. If a machine or a system comes to a sudden stop because there is no 24 V DC control voltage, a complicated restart process has to be initialised. It can happen that a drill or a cutter head gets wedged in a workpiece, which takes a lot of work to fix. Maybe the axles and engines in the system have to be set to neutral in order to ensure a smooth restart. All this - just like troubleshooting - requires a lot of time and when production is down, it's always expensive.

This makes it easy to understand why electronic engineers design their systems so they can carry out targeted shut downs of machines and systems, even after a long mains failures. Servo drive brakes need the time to open safely. The control components should have enough time to finish current processes and to save data.

Buffer modules based on ultra capacitors can help. Energy is stored in high performance capacitors and can be delivered when required. Buffer modules based on capacitors don't require maintenance, which is another great advantage. A comparison: The lead-acid batteries used in conventional uninterrupted power supply (UPS) systems have to be exchanged at regular intervals - for example every three years - because they have a short life span and are only suitable for a small number of charging cycles. This means constantly incurring costs for new batteries and for the service required to change the batteries. By using buffer modules, you can save a lot of money. Buffer modules are installed only once, they can last (with an ambient temperature of 40°C) up to 15 years. Under lower temperatures, the life span can increase up to 60 years.

Manuel Senk, product manager, Interface & Mico at Murrelektronik GmbH told PWE that Murrelektronik's new buffer module Emparro Cap 20/24 1s is designed for a load current of 20 A. It completely buffers the current for a period of over one second - the capacity loss caused by the capacitors' aging is already included in the calculation. On one hand, this long bridging time covers all short and middle mains failures, and on the other hand, it makes it possible to systematically shutdown the peripheral devices that need to be buffered in the event of longer mains failures. With this technology, the productivity of machines and systems is increased without increasing costs. The money spent on the installation is paid off after the first mains failure that was successfully bridged.

Even though Emparro Cap offers a very long buffer time, it is extremely compact. It is only 65mm wide and doesn't need more space than conventional modules, however, the buffer time it provides is five times longer. The wide temperature range of 100 Kelvin (from -40 up to +60°C) makes the buffer module suitable for a wide range of applications: from extremely cold environments like wind turbines to hot environments like control cabinets and terminal boxes.

Maintenance-free and easy to connect terminals with push-in spring technology make installation easy and quick. A data matrix code attached to the product enables direct access to data sheets and product information.

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