RUBYCON CORPORATION
12
TECHNICAL NOTES FOR ELECTROLYTIC CAPACITOR
6. SERIES CAPACITOR CONNECTION
Fig. 6.1
C
1
: Capacitance of Capacitor A
C
2
: Capacitance of Capacitor B
V
1
: Terminal voltage of Capacitor A
V
2
: Terminal voltage of Capacitor B
E: Voltage of Power Supply
When two capacitors are connected in series, voltage
at terminals of each capacitor on charging is applied in
reverse proportion to the capacitance of each capacitor
as shown below.
21
2
1
CC
C
EV
------- 6.1
21
1
2
CC
C
EV
------- 6.2
21
VVE ------- 6.3
This means that voltage applied to either capacitor may
be over the rated capacitor to cause safety vent
operation if capacitance values of them are much
different.
After the completion of charging, terminal voltage on
each capacitor varies with the level of leakage current.
Then over voltage may be applied to the terminals on
either capacitor if another capacitor has high leakage
current, which possibly causes safety vent operation.
To prevent difference in terminal voltage values, it is
useful to put Voltage Distribution Resistors as shown in
Fig. 6.2 and to select two capacitors with little difference
in capacitance. We recommend to use the capacitors in
same production lot.
Follow the formula 6.4 to use Voltage Distribution
Resistors.
Fig. 6.2
I
WV
R x 2 (k) --------- 6.4
WV : Rated voltage (V)
I : Leakage current (mA)
[Specified value after 5 minutes
application of rated voltage]