Rockwell Automation Publication MOTION-AT007A-EN-P - May 2020 39
Regenerative Bus Supply Configurations Chapter 4
AC Line Impedance Considerations
In the following use cases, an additional transformer or line reactor is required due to faults or potential damage associated with AC line
disturbances:
• Installation site has switched power-factor correction capacitors.
• Installation site has lightning strikes or voltage spikes in excess of 6000V peak.
• Installation site has power interruptions or voltage dips in excess of 200V AC.
• The transformer kVA is more than 10 times larger than the drive kVA or the percent source impedance relative to each converter is
less than 0.5%.
In the following use cases, a line reactor is required due to faults associated with sharing AC line-input on multiple converters:
• Repetitive AC input line-voltage notching is present. For example, if silicon-controlled rectifier drive is connected to the same AC
input power source.
- In drive systems that include the regenerative bus supply, repetitive AC line voltage notching can cause the integrated AC line filter
to overheat and result in FLT S18 converter overtemperature faults.
• Powering multiple (two or more) regenerative bus supplies from the same AC input-power source.
- Switching ripple from each regenerative bus supply can interfere with other regenerative bus supplies on the same AC input power
source.
•Powering 2198-Pxxx DC-bus power supply and 2198-RPxxx regenerative bus supply from the same AC input-power source.
- Switching ripple from the regenerative bus supply can impact the temperature of DC-bus capacitors in the DC-bus power supply. In
this use case, a line reactor is required in the AC input-power string leading to the regenerative bus supply.
Refer to Kinetix 5700 Servo Drives User Manual, publication 2198-UM002
, for additional AC line impedance considerations.
Disconnect Switch Considerations
If a disconnect switch is used between the common DC-bus and a PowerFlex 750-Series drive input, connect an auxiliary contact on the
disconnect switch to a digital input of the drive. The corresponding digital input must be set to Precharge Enable. This setting provides the
proper precharge interlocking, which guards against possible damage to the drive when reconnecting the drive to an energized DC-bus.
Under this condition, the drives must have an internal or externally supplied precharge. Precharge handshaking is required before inverter
operation.
When an external precharge device is required, a fuse combination switch can be used. These switches provide precharge of capacitive
loads, have integrated fuse protection, and perform automatic pre-load type functions with an internal coil.
Table 25 - PowerFlex 750-Series Drive Precharge Parameter
Parameter
Digital Input
Number Setting
189 [DI Precharge] See PowerFlex 750-Series AC Drives Programming Manual, publication 750-PM001
.
ATTENTION: To avoid personal injury and/or equipment damage, make sure installation complies with specifications regarding wire
types, conductor sizes, branch circuit protection, and disconnect devices. The National Electrical Code (NEC) and local codes outline
provisions for safely installing electrical equipment.
ATTENTION: The Kinetix 6000 (400V-class), Kinetix 6200/6500, Kinetix 7000, and PowerFlex 750-Series (Frames 5 and 6) AC input
drives have no method for you to control the precharge sequence. To avoid sever drive and/or equipment damage due to uncontrolled
precharge, do not connect these drives to an energized bus. If a disconnect switch is used between the inputs of the drives and the
common DC-bus, an external precharge device must be used.
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