capacitive capacitor paralle with 24 volt dc

[Wolf1977]

hi to all
in an inverter for motor
on input output modul has power supply 24 volt dc is coming from a electrolytic capacitor of main power supply of inverter modul
parallel has an capacitive smd capacitor that is shunt
i want to ask
first what is the play of this capacitor
and what value and voltage do you think must i use for that

[petehall347]

Re: capacitive capacitor paralle with 24 volt dc

filtering i guess .

[stj]

Re: capacitive capacitor paralle with 24 volt dc

electrolytic capacitors are slow - they wont filter high freqiency ripple,
putting a ceramic in parallel is a very old method of fixing this.

ceramics are great at high frequencies but useless at low frequencies - where electrolytics are good.

[Wolf1977]

Re: capacitive capacitor paralle with 24 volt dc

thanks a lot sirs for your answers
and as about as the value and voltage what do you suggest me
the pcb has relationship with input output signals 24 v dc

[stj]

Re: capacitive capacitor paralle with 24 volt dc

35v or higher, capacitance depends on current so i dont know

[Wolf1977]

Re: capacitive capacitor paralle with 24 volt dc

i believe 3 or 4 ampere max
how much is approximately sir ;
can you give me and the equation for calculate the capacitance value ;

[stj]

Re: capacitive capacitor paralle with 24 volt dc

it depends on the capacitor make/series
if you look at the datasheets they give the ripple current.

are you building from scratch or repairing?
because a good question may be how big the capacitor can be in mm.
does it only have one? a lot of invertor circuits have several in parallel so they can use cheaper smaller caps

[Wolf1977]

Re: capacitive capacitor paralle with 24 volt dc

sir is smd
is very small
one other on the same pcb and is connected parallel on other point of the same plug that is similar but is smaller in thickness from the shunt capacitor i desolder it and i measure the capacitance 1 uf
so in your opinion mine that is shunt and is more thickness has smaller or biggger value ;

[stj]

Re: capacitive capacitor paralle with 24 volt dc

bigger volume will give higher ripple,
that 1uf is only for electrical noise suppresion

[Wolf1977]

Re: capacitive capacitor paralle with 24 volt dc

so you suggest to me 1 uf 35 volt right ;

[stj]

Re: capacitive capacitor paralle with 24 volt dc

1uf 50v is the usual size