bonitron M3628PCF, Customer Reference Manual

Page: 23 / 32

User’s Manual
23
7. A
PPENDIX
7.1.
A
PPLICATION
N
OTES
7.1.1.
T
YPICAL
C
APACITOR
B
ANK
F
ORMING
P
ROCEDURE
Electrolytic capacitors undergo physical changes when stored for long
periods. Depending on the ambient conditions of the storage, this can be
from six months to two years. If the capacitors are rapidly taken to their rated
voltage, excessive leakage current may cause them to overheat and fail.
If the capacitor bank is part of a larger system, as a Variable Frequency Drive,
check with the drive manufacturer for specific instructions on how to reform
the capacitor bank.
A short description is below.
1. Attach the output leads to the capacitor bank directly. If you are forming
the capacitors in a drive, ensure that you are directly across the DC bus,
not attached through the braking circuit.
2. Set the voltage control knob to zero.
3. Apply power to the M3628PCF and set the control switch to charge.
4. Slowly raise the output voltage by turning the voltage control knob. Listen
for abnormal sounds or other indications in the capacitors or attached
equipment. Monitor the current indicator to make sure there is not
excessive leakage current, and the voltage indicator to see that the
voltage is rising. Internal bleeder resistors on the capacitor bank may
require current during the process. Consult the equipment manufacturer
for more information.
5. Continue to raise the voltage to the point that the leakage current
stabilizes and the voltage stabilizes at 10-15% of the rated voltage of the
capacitor bank. Let the voltage remain at 10-15% for at least 10 minutes.
6. Increase the voltage on the capacitors by 10-15% again, and wait for 5-
10 minutes.
7. Continue the process until the capacitors are at rated voltage. Always
monitor the capacitor banks or attached equipment for abnormal signs,
such as noise, heating, or smell.
8. Once the capacitor bank is at rated voltage, wait 15 minutes for the
reforming to complete, or consult the equipment manufacturer for a
suitable reforming time.
9. Switch the control switch to Hold and turn the voltage control knob to zero.
10. Allow the capacitor bank to drain either with the bleeder resistors in the
equipment, or by switching the control switch to discharge until the load
voltage is at a safe level, at least below 40VDC.
11. If the procedure is completed successfully, the capacitor bank or
equipment can be returned to storage or put into use.