Given I am charging a 50uF film cap bank to 500V. Do I need a current limiting resistor or some sort of current regulator to minimize inrush current when i first turn on the power supply and/or limit the rate the cap charges?

My concerns are the PS not being able to supply this initial current or possibly damaging the cap bank.

cap datassheet:


  • 3
    \$\begingroup\$ It's possible that you do but it depends on details that are not included in the question. Read the power supply's data sheet and ditto the cap bank. When you've finished with the data sheets please look at questions you've previously asked and formally accept some answers so that folk don't think you are a freeloader. \$\endgroup\$
    – Andy aka
    Dec 5, 2018 at 18:08
  • \$\begingroup\$ There, I bet that makes you feel all chrismassy! \$\endgroup\$
    – Andy aka
    Dec 5, 2018 at 18:20
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    \$\begingroup\$ Checkout page 4 of the cap data sheet - middle column. You need to limit the rate of rise of voltage to what it states (7 V per us). \$\endgroup\$
    – Andy aka
    Dec 5, 2018 at 18:21
  • \$\begingroup\$ So In order to determine how many us the cap would take to charge, would that just depend on the power supply? we dont have one selected specifically yet.. \$\endgroup\$
    – lightro
    Dec 5, 2018 at 18:30
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    \$\begingroup\$ make sure you have an appropriately rated resistor, 500V and 50uF is pretty dangerous, definitely enough to kill you \$\endgroup\$
    – BeB00
    Dec 5, 2018 at 19:34

1 Answer 1


It's common to use a circuit like this known as pre-charge stage. Initially you limit the inrush with the resistor and then you shunt it with the relay contact. Also, there are inrush current limiters (thermistors) for this with the disadvantage they heat up a lot. One needs more details about your application in order to give better answers.

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