In Electrical, What is the difference between DC capacitors and AC capacitors?

What is the purpose of capacitors in the electrical/electronic Circuit in general?

How about in UPS system (Uninterruptible power supply)?

3 Answers

  • LG
    Lv 7
    9 months ago

    AC capacitors will work with any polarity, whilst DC capacitors will only work with one polarity. An AC capacitor can work in a DC application, but a DC capacitor won't work in an AC application(where the polarity of the charge on the capacitor can flip). One might ask "why use DC capacitors at all?". And the answer would be that AC capacitors are usually significantly larger and more expensive for the same voltage and capacitance rating than DC capacitors.

    Capacitors perform a variety of functions in circuits such as energy storage for short term demands in power supplies, signal coupling in AC circuits, tuning for frequency generators, power factor correction in AC power systems, stability control in amplifiers, and in filters.

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  • 9 months ago

    There's no such thing as DC and AC capacitors.

    They can be used for DC blocking, AC passing, decoupling, coupling, energy storage, tuned circuits, and may other use cases.

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  • 9 months ago

    Capacitors are used for such as short term energy storage, as in with smoothing or reservoir type applications in power supplies, and for coupling signals between circuits at different DC levels.

    In general, DC rated capacitors often use an electrochemically produced insulating layer (think like anodised aluminium) as the insulator between capacitor plates. Connecting to the wrong polarity can break that layer down and cause the capacitor to fail.

    AC rated capacitors normally use plastic film or oiled paper as the insulating layer (dielectric) between the capacitor plates. That's a mechanical separator and not affected by polarity.

    There are many variations, but that's for the commonest types.

    You can think of a capacitor as a bit like a pipe with an elastic diaphragm across it, in a fluid system.

    Connected across a pressure (voltage) source like pump or rectifier, it charges up (the diaphragm stretches) and it can maintain the output pressure through monetary gaps in the feed from the pump/rectifier.

    Between two sections of a system with different static pressures, it will pass variations in pressure without allowing continuous flow; eg. it passes the AC component without any DC flow.

    This is a smoothing or reservoir example:

    The caps in this are used for coupling; they allow the amp circuit to internally run at various DC offset levels (needed for it to work) but without any DC flow back through the input or to the loudspeaker:

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