12 Rockwell Automation Publication MOTION-AT007A-EN-P - May 2020
Chapter 1 DC-bus Wiring Guidelines
When multiple drives are connected through disconnects to a common DC-bus, it is necessary to provide an input to the drive that enables
the precharge to finish. Often, an auxiliary contact on the drive disconnect switch controls this input.
Figure 5 - Common DC-bus Example
If Precharge Enable is selected as a digital input, it must be energized to let the initial bus precharge complete. If Precharge Enable is de-
energized, it is treated as a coast-to-stop command that forces the drive to the initial bus-precharge state. Fuse failure is probable unless
coordination of precharge circuits in individual drives is implemented.
When Kinetix 6000 drives are used in common bus configurations, they must have firmware revision 1.92 or later. Kinetix 6200/6500 drives
with any firmware revision can be used.
PowerFlex 750-Series (Frame 1…4) AC Drives
For PowerFlex 750-Series frame 1…4 AC drives, the precharge hardware is on the power circuit board. It is composed of a resistor in series
with the positive DC-bus, between the DC link and the bus capacitors. The resistor has a relay contact that is connected in parallel, which
closes to bypass the Precharge resistor when the bus precharge level is attained. The precharge function operates the same way for either
AC or DC input power.
Figure 6 - AC and DC Input Schematic for PowerFlex 750-Series (Frame 1…4) AC Drives
ATTENTION: The Precharge Enable digital input is only available on PowerFlex 750-Series common-bus inverter drives. The Kinetix
servo drives do not include a Precharge Enable digital input.
ATTENTION: The bus capacitors in the individual drives act as a low-impedance voltage source. Extra care is needed when connecting
individual drives to an energized bus.
ATTENTION: Kinetix drives have no method for you to control the precharge sequence. To avoid severe drive and/or equipment
damage due to uncontrolled precharge, do not connect Kinetix servo drives to an energized DC-bus.
DC –
BR2
L1
L2
L3
U
V
W
DC+
BR1
+
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