EPM Series Application Notes
Rev.3.1 May, 2013
TAMURA CORPORATION
8 / 17
③Calculate the guaranteed life of the electrolytic capacitor and check that there is no problem.
Since the life calculation expression is different depending on the capacitor manufacturer and type, requesting life
calculation by the manufacturer of the capacitor used is recommended.
Generally, life can be calculated by using the temperature and ripple current of the electrolytic capacitor.
1)Electrolytic capacitor temperature
The temperature at which the temperature on the body of the electrolytic capacitor is maximum is measured
and is made a life calculation parameter.
2)
Ripple current
For AC input, a charging current (IL) and discharging current (IH) flow in the input smoothing electrolytic
capacitor. These currents are measured individually and frequency correction is performed on IH and it is
made a life calculation parameter as 120Hz ripple current.
The ripple current (I120) frequency corrected to 120Hz is calculated from the following expression:
2
H
2
L
120
)
fc
)
rms
(
I
(
)
rms
(
I
)
rms
(
I
⋅
+
=
fc: Frequency correction coefficient (Refer to the electrolytic capacitor catalog.)
For stable DC input, the ripple current by high frequency charging/discharging current is assumed for input
electrolytic capacitor.
Discharging current (high frequency)
Effective value: IH (rms)
Charging current (low frequency)
Effective value: IL (rms)
AC input
Input current: IDC (ms)
DC input
