Using kinetic energy to protect PLCs
07 March 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.
Most 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. Directly connecting the DC-bus to this power supply avoids the need for a separate low voltage supply for control equipment, says the company.
If a mains failure occurs, the power supply 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. This energy has, traditionally, not be usable owing to the high EMC levels present, however improved filtering technology developed by PULS now makes it possible.
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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