Table of Contents
Advertisement
MicroHarmony Cell Sizes 40 - 260A Manual
If reforming is performed with the cells connected in the drive, connect the variable voltage source to a cell who's
output is connected to the wye output connection of the drive (i.e., cell C1). Connect the leads to the cell's three
phase input terminals or to its transformer secondary.
Caution: Reforming the cells connected in the drive will back feed the main input transformer;
medium voltage will be present and the transformer will be energized. Exercise extreme caution.
Remember that the cell chassis are floating (not grounded).
If reforming is performed with the cell out of the drive, connect the variable voltage source to the three phase input of
the cell. Exercise extreme caution- unless an input isolation transformer is used and the chassis is wired to ground,
the voltage is present from the cell to ground.
1.
Hook a voltmeter up to the variable voltage source, across two phases.
2.
Slowly raise the voltage to 100Vrms. Hold for 15 minutes.
3.
Slowly raise the voltage in 100Vrms increments, holding each for 15 minutes.
4.
Once 825Vrms is reached, hold for 15 minutes and shut down.
5.
Allow the cell bus voltage to bleed down completely before removing the variable voltage source.
Energize the drive by turning on the medium voltage input and leave power on for at least 1 hour before operating the
drive.
9.8.3
Failure Modes
Early-Life Failures
Early-life failures, infant mortals, are mostly short-circuit failures from weaknesses in the aluminum oxide dielectric.
Incidence can be reduced with extended aging or burn-in.
Wear-Out
In the case of large capacitors enduring high levels of ripple current, the increasing ESR can cause overheating and
short circuit failures as wear-out failures. Open-circuit wear-out failures are caused by a loss of electrolyte or ESR
increase from other causes.
9.8.4
Useful Life Calculations
Onset of wear-out is determined mainly by the capacitor's size and average operating temperature. Operating voltage
has some effect. For capacitors operating at moderate temperatures, the operating life doubles for each 10 °C that
operating temperature is reduced. The inevitable death of an aluminum electrolytic capacitor is defined differently
from one vendor to the next, and formulas for forecasting end of life differ as well.
United-Chemi Con's life model has been proven to be effective in forecasting the useful life of their capacitor. UCC
defines end of life as a 20% capacitance loss, 2 times the initial ESR specification and initial DC leakage current
specification. Life is not guaranteed beyond 15 years.
19001467: Version 1.0
s
Application Notes
9
9-15
Advertisement
Table of Contents
