Film capacitor overheats at 6 Amps rms?

[grizedale]

Hi,


The following capacitor (1uF, 400V = ECWF4105) has an esr of 1.52 at 84KHz.

the datasheet page 6 tells this..............

CAP DATASHEET
**broken link removed**

Page 7 tells that this cap can handle 6 Amps of ripple current at 84KHz.

....but that would mean this capacitor dissipating 54W of power, which it surely could not possibly do?

 

[FvM]

There's no ESR specification in the datasheet. The impedance curves suggest an ESR (= minimum value of impedance) of several 10 milliohm, which sounds reasonable.

 

[grizedale]

Hi,

The middle graph, page 6, RHS, tells us that the dissipation factor for 1uF, 400V at 84KHz......is around 0.8.....meaning 1.3 Ohms esr

 

[mtwieg]

Hi,

The middle graph, page 6, RHS, tells us that the dissipation factor for 1uF, 400V at 84KHz......is around 0.8.....meaning 1.3 Ohms esr

What? Where does it say dissipation factor is 0.8? Maybe you're confusing it with pin diameter?

By my reading of the D graph, it should be around 0.5%.

 

[grizedale]

woops. thanks for that, i was forgetting that DF is in %, and the 0.8, is actually 0.008......or 0.005 depending on how the graph is extrapolated.

so esr = DF.XC = 9.47mR ...sounds better......