Prevent 24VDC Overloads from Stopping Production


Advanced technologies require more intelligent protection. For today’s preferred switched mode power supplies, it means that circuit breakers and fuses are inadequate for protecting individual 24 VDC load circuits.

Along with the laws of physics, engineers have to be aware of the law of unintended consequences. Take, for example, something as simple as the 24 VDC power supplies that feed the control circuits in automation systems. Years ago, these were linear units containing an input transformer, a bridge rectifier and some filtering, with a series-type voltage regulator. They were rugged and dependable, but big, heavy and not very efficient. Although they handled overloads and rarely failed, linear power supplies wasted energy and pumped heat into control cabinets.

The answer was the switch-mode power supply, which is both smaller and more energy-efficient than the old linear unit. Switch-mode power supplies have become the most common type used today, but they have one characteristic that causes problems that linear supplies did not: The way they respond to overloads or short circuits.

Author: Kai Bronzel, Siemens  | File Type: PDF

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