Baldor MicroFlex, Installation Manual

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3-12 Basic Installation MN1919
3.4.3 Input power conditioning
Certain power line conditions must be avoided; an AC line reactor, an isolation transformer or
a step up/step down transformer may be required for some power conditions:
H
If the feeder or branch circuit that provides power to the MicroFlex has permanently
connected power factor correction capacitors, a suitable input AC line reactor or an
isolation transformer must be connected between the power factor correction capacitors
and the MicroFlex to limit the maximum symmetrical short circuit current to 5000A.
H
If the feeder or branch circuit that provides power to the MicroFlex has power factor
correction capacitors that are switched on line and off line, the capacitors must not be
switched while the drive is connected to the AC power line. If the capacitors are switched
on line while the drive is still connected to the AC power line, additional protection is
required. A Transient Voltage Surge Suppressor (TVSS) of the proper rating must be
installed between the AC line reactor (or isolation transformer) and the AC input to the
MicroFlex.
3.4.3.1 Input power-cycling and inrush
If AC power has been removed from the MicroFlex, it should remain disconnected for the
period specified in Table 1, before it is reapplied.
MicroFlex
current rating
Minimum power cycle delay period
(seconds)
1A, 3A 25
6A 45
9A 65
Table 1 - Power cycle intervals
This delay allows the input surge protection circuit to perform correctly, ensuring that the
inrush current (typically 1.7A) is below the drive rated current. Power-cycling the drive more
frequently could cause high inrush current and corresponding nuisance operation of circuit
breakers or fuses. Repeated failure to observe the delay period could reduce the lifetime of the
MicroFlex.
3.4.3.2 Discharge period
DANGER : After AC power has been removed from the MicroFlex, high voltages
(greater than 50VDC) will remain on the regeneration resistor connections
until the DC-bus circuitry has discharged. The high voltage will remain for
the period specified in Table 2.
MicroFlex
current rating
Time for DC-bus to discharge to 50V or less
(maximum, seconds)
1A, 3A 83
6A 166
9A 248
Table 2 - DC-bus discharge periods