Digital Inputs 2-59
• Precharge Enable (PowerFlex 700 only)
This input function is used to manage disconnection from a common DC
bus.
If the physical input is closed, this indicates that the drive is connected to
common DC bus and normal precharge handling can occur, and that the
drive can run (start permissive). If the physical input is open, this
indicates that the drive is disconnected from the common DC bus, and
thus the drive should enter the precharge state (precharge relay open) and
initiate a coast stop immediately in order to prepare for reconnection to
the bus.
If this input function is not configured, then the drive assumes that it is
always connected to the DC bus, and no special precharge handling will
be done. This input function is used in PowerFlex 700 drive only. In
PowerFlex 70 drives, the drive assumes it is always connected to the DC
bus.
Digital Input Conflict Alarms
If the user configures the digital inputs so that one or more selections
conflict with each other, one of the digital input configuration alarms will be
asserted. As long as the Digital Input Conflict exists, the drive will not
start. These alarms will be automatically cleared by the drive as soon as the
user changes the parameters so that there is an internally consistent digital
input configuration.
Examples of configurations that cause an alarm are:
• User tries to configure both the “Start” input function and the “Run
Forward” input function at the same time. “Start” is only used in
“3-wire” start mode, and “Run Forward” is only used in “2-wire” run
mode, so they should never be configured at the same time
• User tries to assign a toggle input function (for instance “Forward/
Reverse”) to more than one physical digital input simultaneously.
• These alarms, called Type 2 Alarms, are different from other alarms in
that it will not be possible to start the drive while the alarm is active. It
should not be possible for any of these alarms to occur while drive is
running, because all configuration parameters are only changeable while
drive is stopped. Whenever one or more of these alarms is asserted, the
drive ready status will become “not ready” and the HIM will reflect a
message signaling the conflict. In addition, the drive status light will be
flashing yellow.
There are three different digital input configuration alarms. They appear to
the user (in [Drive Alarm 2]) as “DigIn CflctA”, “DigIn CflctB”, and “DigIn
CflctC”.
“DigIn CflctA” indicates a conflict between different input functions that
are not specifically associated with particular start modes.
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