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8.8.2. Recharging the capacitors in stored units
When complete AC Drive units are stored without any voltage being applied to them,
the recharging of the capacitors should be done at least every 12 months, by connect-
ing the power supply to the unit and then keeping the unit powered up for a minimum
of one hour.
If the storing time is much longer than one year, the recharging of the capacitors has to
be done in a way that possible high leakage current through the capacitors is limited.
The best alternative is to use a DC-power supply with an adjustable current limit. The
current limit has to be set, for example, to 300…500mA and the DC-power supply has
to be connected to the B+/B- terminals (DC+ to B+, DC- to B-) of the DC-link or
straight to the capacitor terminals.
NX product, which have no B+ / B- terminals, can be powered up as follows:
•
Frame size FR8-FR9: the DC supply is connected between the two input phases L1,
L2.
•
The DC voltage has to be adjusted up to the nominal DC voltage level of the unit
(1.35*Un AC) and has to be supplied for at least one hour.
•
If a DC voltage is not available and the unit has been stored much longer than one
year de-energized, consult the manufacturer before connecting the power.
8.8.3. Recharging individual capacitors that have been stored
When using spare part capacitors from stock and it is known that they have been
stored there for over one year uncharged, it is easiest to recharge the capacitors before
they are installed in a unit.
The DC power supply current limit is set to 50…100 mA and the voltage is set to the
rated value of capacitors. The recharging process can be then followed by monitoring
the current meter of the DC-power supply. It is recommended to keep voltage supplied
for at least one hour even though the leakage current has already stabilized earlier.
Due to high leakage resistance, a dangerously high voltages can remain in capacitors
for a long time. So, remember to discharge the capacitors, by using the correct dis-
charging resistor, after the recharging is finished.
FIGURE 1. How to connect the DC power supply
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+
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V
I
R
