capacitance calculation along dc source

[zeeshan728]

hi,
I want to determine the rating of capactior which is connected in parallel to the DC voltage source..the rating of DC source is 20kV and 20 mA...i Donot know how to interpret this problem..If someone has any idea kindly share..thanks.

 

[enjunear]

The voltage on the capacitor will be equal to the voltage of the power supply, so it should have a rated voltage of at least 20kV. In practice, you typically oversize the cap's voltage rating, depending on the type of capacitor used and potential voltage transients that can occur. In most of my systems, we operate with 28Vdc, so I go with 50V or 100V parts. I'm not sure how that translates to the kV range... you may just derate by some percentage?

 

[zeeshan728]

The voltage on the capacitor will be equal to the voltage of the power supply, so it should have a rated voltage of at least 20kV. In practice, you typically oversize the cap's voltage rating, depending on the type of capacitor used and potential voltage transients that can occur. In most of my systems, we operate with 28Vdc, so I go with 50V or 100V parts. I'm not sure how that translates to the kV range... you may just derate by some percentage?

thanks for your reply,,
it means the voltage rating of capacitor will be roughly double of input voltage...but what will be the capacitance rating is it will in nanoFarad or picoFarad..how to calculate that... ??? as the frequency in this case will be zero....

 

[enjunear]

thanks for your reply,,
it means the voltage rating of capacitor will be roughly double of input voltage...but what will be the capacitance rating is it will in nanoFarad or picoFarad..how to calculate that... ??? as the frequency in this case will be zero....

The capacitance should be determined by what the cap is supposed to do. If this is being used for bulk energy storage, then the value will typically be big.... mF or Farads. For filtering of smaller transient signals, the values will more commonly be in the nF and uF range. This is highly dependant on the load and desired output ripple performance.

 

[zeeshan728]

The capacitance should be determined by what the cap is supposed to do. If this is being used for bulk energy storage, then the value will typically be big.... mF or Farads. For filtering of smaller transient signals, the values will more commonly be in the nF and uF range. This is highly dependant on the load and desired output ripple performance.

i wana use this capacitor as a energy storage device..so that if there is some fluctuation in the input dc voltage then it compensate that fluctuation and in turn gives steady voltage at the output....bcoz in previous dc source rise time is large...and i want to reduce this rise time to micro or nano seconds using fast switching relays...in the end whole device will be capable of generating 20 kV