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Power supply utilises kinetic energy to protect PLC systems

14 February 2012

PULS UK is urging companies to make use of kinetic energy produced by ac electric motors to safeguard PLC control circuits in the event of a mains failure using its QTD20 power supplies. Modern production machines use ac motors controlled by frequency converters or servo amplifiers and have an intermediate dc-bus to which all individual drives are connected. By connecting the PULS QTD20 directly to the dc-Bus the need for a separate low voltage supply for control equipment can be avoided.

If a mains failure occurs, the QTD20 utilises the power from the dc-bus capacitors, which are charged from the kinetic energy of the motor, to support the PLC until the motor has come to a complete stop. This ensures the control equipment and other important peripheral equipment is kept operational long enough for a controlled shutdown to take place. Until recently this energy was not usable owing to the high EMC levels present, however improved filtering technology developed by PULS has now made this possible.

“When power failure occurs it’s the time taken to reset the system that causes the main disruption to production,” said PULS’s managing director, Harry Moore. “Even a half-second outage means that you need to find out where you were when the interruption happened so you can restart the PLC from the relevant point. Of course, most people will use some kind of UPS back-up system, but with the QTD20 we can use the energy from the slowing motor to generate enough current to shut everything down properly.”

The QTD20 features 600Vdc input voltage optimised for intermediate dc-buses of drive systems, efficiency up to 95% with 125% peak load capability, active input transient filter, full output power in extreme temperatures of between -25°C and +60°C, minimal inrush current, reverse input polarity protection and dc-ok relay contact.


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