How to make capacitor

[JohnJohn20]

Hello
What is difference between dc and ac capacitor as dc work on 26v and capacitor work 440v

 

[DPG]

Hello
What is difference between dc and ac capacitor as dc work on 26v and capacitor work 440v

Capacitors work at a wide range of voltages and perform many functions (smoothing, DC blocking, coupling, motor starting, etc). They are all fundamentally based on two electrodes and a gap though.

Have a Google search.

 

[JohnJohn20]

Hello
How capacitor are made how aluminum
Store voltage and current

 

[DPG]

Hello
How capacitor are made how aluminum
Store voltage and current

Too big a topic to answer in a forum post.

Where is Google?

 

[Simon47]

Need to narrow down the question a bit.
If we stick to one type as hinted at, aluminium electrolytic, then a few things are easier to answer.
Basically, these are two sheets of aluminium with two sheets of separator, would very tightly into a spiral - like a toilet roll. The separator, which could be paper or plastic, sets the distance between the sheets. In some types, the aluminium film surface is oxidised, and this oxide layer forms the insulator - the thicker it is, the higher the voltage rating. In others, the plastic (or dry paper) is the insulator.
DC or AC is down to how the insulating layers have been formed, and the internal chemistry. I vaguely recall that if the insulator is a formed oxide layer, then reversing the polarity will "unform" this, destroying the insulating layer and effectively causing the cap to go short circuit. If the insulator is the plastic or paper sheet, then it's inherently bipolar as (contrary to what some electricians have told me in the past*) the plastic doesn't care which way the voltage is.

And once you get into it, there's a lot more to understand regarding ripple currents and stuff like that.
If you apply a steady DC to a cap, then once it's charged, no more current will flow (apart from a small amount of leakage). If there is ripple, or it's AC, then periodic currents will flow - creating heating in the internal resistance (see a specification called ESR - effective series resistance). Any specific capacitor will have a power limit - and hence why there is such a choice of capacitors available. For high-ripple applications you would want something with a low ESR. For an intermittent application (such as a motor start capacitor) it could have a lower rating as it will have time to cool down between uses. But for a non-intermittent application, it would need to cope with the power dissipation over a longer period (such as for a motor run application). And for pulse application (handing short high rise rate pulses instead of sine waves) different design considerations come into play - which are beyond my knowledge.

* I jest not, on one occasion an electrician told me that my data cables could only use one section of the trunking (despite it not being big enough and he'd used the much bigger section for a couple of 2.5mm T&Es) as "it the divider wouldn't insulate if they were swapped round".

 

[DPG]

Need to narrow down the question a bit.
If we stick to one type as hinted at, aluminium electrolytic, then a few things are easier to answer.
Basically, these are two sheets of aluminium with two sheets of separator, would very tightly into a spiral - like a toilet roll. The separator, which could be paper or plastic, sets the distance between the sheets. In some types, the aluminium film surface is oxidised, and this oxide layer forms the insulator - the thicker it is, the higher the voltage rating. In others, the plastic (or dry paper) is the insulator.
DC or AC is down to how the insulating layers have been formed, and the internal chemistry. I vaguely recall that if the insulator is a formed oxide layer, then reversing the polarity will "unform" this, destroying the insulating layer and effectively causing the cap to go short circuit. If the insulator is the plastic or paper sheet, then it's inherently bipolar as (contrary to what some electricians have told me in the past*) the plastic doesn't care which way the voltage is.

And once you get into it, there's a lot more to understand regarding ripple currents and stuff like that.
If you apply a steady DC to a cap, then once it's charged, no more current will flow (apart from a small amount of leakage). If there is ripple, or it's AC, then periodic currents will flow - creating heating in the internal resistance (see a specification called ESR - effective series resistance). Any specific capacitor will have a power limit - and hence why there is such a choice of capacitors available. For high-ripple applications you would want something with a low ESR. For an intermittent application (such as a motor start capacitor) it could have a lower rating as it will have time to cool down between uses. But for a non-intermittent application, it would need to cope with the power dissipation over a longer period (such as for a motor run application). And for pulse application (handing short high rise rate pulses instead of sine waves) different design considerations come into play - which are beyond my knowledge.

* I jest not, on one occasion an electrician told me that my data cables could only use one section of the trunking (despite it not being big enough and he'd used the much bigger section for a couple of 2.5mm T&Es) as "it the divider wouldn't insulate if they were swapped round".

I'd read his other posts as well if I were you.

 

[johancarter]

A DC capacitor is designed to work at DC voltages, while an AC capacitor is designed to work at AC voltages. DC capacitors are typically used in power supplies and DC circuits, while AC capacitors are typically used in AC circuits and AC-powered devices. Read this topic: What is the Difference Between AC and DC Capacitor? - AutomationForum - https://automationforum.co/what-is-the-difference-between-ac-and-dc-capacitor/

 

[Simon47]

Bit of old thread revival ...

Oh dear, from that page :
"Thus, the frequency of the input signal, which is continuously charged (or discharged), determines the capacitance of the capacitor in AC circuits". Err, the capacitance is fixed by the construction of the cap, it's IMPEDANCE (complex relation to resistance) varies with frequency and is 1/(2*pi*f*C).