Rockwell Automation 20D PowerFlex 700S AC Drives with Phase II Control Reference Manual User Manual
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Rockwell Automation Publication PFLEX-RM003E-EN-E - January 2011
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Detailed Drive Operation Chapter 1
1.
A user-controlled precharge enable must be present. The precharge enable
can be provided by a hardware input or parameter configuration. When
one of the digital input selection parameters (825…830 [Dig Inx Sel]) is set
to 30 “PreCharge En”, the hardware precharge control is selected and the
digital input controls the user precharge enable. If none of the digital
inputs are set to precharge enable, the control then uses parameter 411
[PreChrg Control] as the source for the precharge enable. In this case,
when parameter 411 = 0 “Hold PrChrg”, the precharge control is disabled
(held in precharge) and the drive is inhibited from running. Otherwise,
when parameter 411 = 1 “Enbl PrChrg”, the user precharge is enabled.
Using a digital input for the precharge enable is recommended for
common bus systems where a drive may be disconnected and reconnected
to the common bus system. The digital input should be connected through
an auxiliary contact on the cabinet disconnect switch. Failure to provide a
hardware disconnect precharge control may lead to very large inrush
currents and associated drive damage if a reconnection is made before the
drive can sense the power loss. This precharge enable provides a user
controlled permissive to the precharge function.
2.
The drive must not be in an undervoltage condition. Parameter 409 [Line
Undervolts] sets the undervoltage level as a percentage of drive rated volts
(parameter 401 [Rated Volts]). An undervoltage is detected by comparing
the value of parameter 306 [DC Bus Voltage] to the percentage of line
voltage set in parameter 409 [Line Undervolts] times parameter 401
[Rated Volts] times the square root of 2. The undervoltage condition is
displayed in parameter 555 [MC Status] bit 15 “DC Bus Low”.
3.
The drive bus voltage must be stable (not rising). The bus voltage stable
condition is determined by comparing the bus voltage to a filtered value of
the bus voltage. Initially, when power is applied to the drive the bus voltage
will rise as determined by the limited current controlled by the precharge
device. The filtered value of bus voltage will lag behind the actual bus
voltage until the bus capacitor charging is complete, then the values will
converge. A difference between the filtered and actual bus voltage
determines if the bus voltage is stable.
4.
The drive must not be running (PWM active), except in coordination with
ride through. After the initial drive precharge has completed, a power loss
may present conditions for precharge to be restarted (ex. low bus voltage).
However, if the drive output is active (parameter 155 [Logic Status], bit 0
“Active” = 1), the restart of precharge will be inhibited until the drive is
stopped (PWM not active). Also refer to
for controller coordinated PWM disable and precharge
operation. If the drive is running and the user removes the precharge
enable, this condition will be ignored until the drive is disabled (PWM
stops). Then the precharge function will be started again.