Rockwell Automation Publication 2198-UM002L-EN-P - October 2021 43
Chapter 2 Plan the Kinetix 5700 Drive System Installation
AC Line Impedance Considerations
DC-bus power supplies do not require an isolation transformer for three-
phase input power. Regenerative bus supplies also do not require an isolation
transformer for three-phase input power unless they are connected to corner-
grounded or ungrounded facility power. See Input Power Configurations for
Kinetix 5700 Power Supplies on page 121 for example configurations.
A transformer can be required to match the voltage requirements of the power
supply to the available service. For the AC input voltage requirements, refer to
the Kinetix 5700 power specifications in the Kinetix 5700, 5500, 5300, and 5100
Servo Drives Specifications Technical Data, publication KNX-TD003
.
Use a safety factor of 1.5 for three-phase power (where safety factor is used to
compensate for transformer, drive modules, motor losses, and to account for
utilization in the intermittent operating area of the torque speed curve).
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 fault.
IMPORTANT
These recommendations are advisory and do not address all situations.
Site-specific conditions must be considered for proper installation.
IMPORTANT
When using an autotransformer, make sure that the phase to neutral/
ground voltage does not exceed the input voltage ratings of the power
supply.
EXAMPLE
Sizing a transformer to the voltage requirements of this power supply:
2198-P141: 31kW x 1.5 = 46.5 kVA transformer.
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