ENG_67765.XML
Power supplies
In plant building or mechanical equipment manufacture, or in any other situations in which electrical controls are used, a safe and reliable power supply is needed to supply the process with power.
The operational reliability of electronic controls and associated reliable operation of automated plants is extremely closely linked to the resistance of the load current supply to failure. Final control elements as well as input and output modules will only respond to command signals if the power supply is operating reliably.
In addition to requirements such as safety, particular demands are placed on the electromagnetic compatibility (EMC) of the power supply with reference to the tolerance range of the output voltage, as well as its ripple.
Important factors that determine problem-free implementation are, in particular:
- An input current with a low harmonic content
- Low emitted interference
- Adequate immunity (noise immunity) to interference
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EMC
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Interference phenomena
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Emission (emitted interference)
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Interference caused by television and radio reception
Interference coupling on data lines or power supply cables
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Noise immunity (immunity to interference)
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Faults on the power cable due to switching non-resistive loads such as motors or contactors
Static discharge due to lightning strikes
Electrostatic discharge through the human body
Conducted interference induced by radio frequencies
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Selected interference phenomena
General notes on DC power supplies
The DC power supply is a static device with one or more inputs and one or more outputs that converts a system of AC voltage and AC current and/or DC voltage and DC current to a system with different DC voltage and DC current values by means of electromagnetic induction for the purpose of transmitting electrical energy.
The type of construction of a DC power supply is primarily decided by its intended use.
