Can someone once and forall tell me what a capacitor does in an AC circuit?Thanks.

[Pcg127]

Can someone tell me once and for all, what a capacitor does in an AC circuit?

 

[plugsandsparks]

It accumulates charge and then discharges to the best of its ability.
Hope this helps

 

[telectrix]

this will help.

https://www.electronics-tutorials.ws/capacitor/cap_8.html

 

[loz2754]

Lots of things. It can smooth the bump of a rectified waveform.
It can block DC.
It can be used in conjunction with an inductor to reduce EMI.
And ashit ton of other stuff.

Why the "once and for all"? Has this been on your mind for a while?

 

[telectrix]

can also be used to correct power factor of an inductive load.

 

[telectrix]

a useful function is to charge up to a dc voltage, put in toolbox. plumbers and customers' carpet crawlers and cats will then learn to keep their grubby mitts out.

 

[pc1966]

There are different ways to look at it, but one analogy is:

• Capacitors try to prevent voltage changing
• Inductors try to prevent current changing

So when you try to increase the voltage across a capacitor you need to put current in to charge it, this makes it hard to change voltage suddenly as the required current is given by I = C * dV/dt so a capacitor provides "smoothing" and stores electric charge in doing so.

An inductor need a voltage applied in order to change the current flow. So if you try to interrupt current in an inductive circuit (e.g. motor, relay coil, etc) you get a high voltage generate opposing that. The voltage is given by V = L * dI/dt and that can cause damage to switches or solid state controls, but is sometimes of use in cases such as car ignition coils.

The rate of change terms (dV/dt and dI/dt) for the useful case of a sine wave is given by 2 * PI * f which leads to the concept of capacitive and inductive reactance, analogous to resistance in opposing current flow, but not in-phase with the voltage as it is the changing aspect that matters. That is at its maximum when the voltage is crossing zero.

 

[telectrix]

There are different ways to look at it, but one analogy is:

• Capacitors try to prevent voltage changing
• Inductors try to prevent current changing

So when you try to increase the voltage across a capacitor you need to put current in to charge it, this makes it hard to change voltage suddenly as the required current is given by I = C * dV/dt so a capacitor provides "smoothing" and stores electric charge in doing so.

An inductor need a voltage applied in order to change the current flow. So if you try to interrupt current in an inductive circuit (e.g. motor, relay coil, etc) you get a high voltage generate opposing that. The voltage is given by V = L * dI/dt and that can cause damage to switches or solid state controls, but is sometimes of use in cases such as car ignition coils.

The rate of change terms (dV/dt and dI/dt) for the useful case of a sine wave is given by 2 * PI * f which leads to the concept of capacitive and inductive reactance, analogous to resistance in opposing current flow, but not in-phase with the voltage as it is the changing aspect that matters. That is at its maximum when the voltage is crossing zero.

here endeth the first lesson.

 

[Pcg127]

There are different ways to look at it, but one analogy is:

• Capacitors try to prevent voltage changing
• Inductors try to prevent current changing

So when you try to increase the voltage across a capacitor you need to put current in to charge it, this makes it hard to change voltage suddenly as the required current is given by I = C * dV/dt so a capacitor provides "smoothing" and stores electric charge in doing so.

An inductor need a voltage applied in order to change the current flow. So if you try to interrupt current in an inductive circuit (e.g. motor, relay coil, etc) you get a high voltage generate opposing that. The voltage is given by V = L * dI/dt and that can cause damage to switches or solid state controls, but is sometimes of use in cases such as car ignition coils.

The rate of change terms (dV/dt and dI/dt) for the useful case of a sine wave is given by 2 * PI * f which leads to the concept of capacitive and inductive reactance, analogous to resistance in opposing current flow, but not in-phase with the voltage as it is the changing aspect that matters. That is at its maximum when the voltage is crossing zero.

Yes but can I use capacitors to increase voltage across motor windings?

 

[Pcg127]

Yes but can I use capacitors to increase voltage across motor windings?

Lots of things. It can smooth the bump of a rectified waveform.
It can block DC.
It can be used in conjunction with an inductor to reduce EMI.
And ashit ton of other stuff.

Why the "once and for all"? Has this been on your mind for a while?

If I had a capacitor across a winding in a three phase motor, then what difference would that make?