Rockwell Automation SA3100 AC Power Modules - Manual (Page 26)

3-8 SA3100 Power Modules
3.3 AC Supply Source Requirements
SA3100 Power Modules are suitable for use on grounded supply circuits capable of
delivering up to a maximum of 200,000 rms symmetrical amperes, 600 volts
maximum, when used with the AC input line fuses specified in
table 3.1. Conditioning
of the AC line may be required for an unbalanced distribution system, or a system with
a low impedance relative to the Power Module input.
Important: SA3100 Power Modules are designed to operate on resistance-grounded
or hard-grounded distribution systems. See figure 3.11. Operation on
ungrounded distribution systems is not recommended.
3.3.1 Determining if an Isolation Transformer or Line Reactor is
Required
The AC line should have a minimum impedance of 1% (3% for 0.37 - 22 kW/0.5 - 30
HP drives) relative to the rated input kVA of the Power Module (see Appendix A). If
the line has a lower impedance, a line reactor or isolation transformer must be added
before the input to increase line impedance. If the line impedance is too low, transient
voltage spikes or power interruptions could result in nuisance fuse blowing,
overvoltage faults, or damage to the Power Module.
In general, an isolation transformer or line reactor (5% impedance) is required if:
• the AC line frequently experiences transient power interruptions or significant
voltage spikes, or
• the kVA capacity of the AC line is greater than 4 times the kW (HP) rating of the
motor, or
• the AC line has power factor correction capacitors connected, or
• the drive is operated on an unbalanced distribution system. Refer to section 3.3.2.
3.3.2 Isolating an Unbalanced Distribution System
SA3100 Power Modules are designed to operate on conventional three-phase
supplies with line voltages that are symmetrical with respect to ground. The input is
equipped with metal oxide varistors (MOVs) to provide voltage surge protection and
line-to-line plus line-to-ground protection in conformance with IEEE 587. The MOV
circuit is designed for surge suppression only (transient line protection), not
continuous operation.
The Power Module should not be used directly with supplies in which the
line-to-ground voltage on any phase can exceed 125% of the nominal line-to-line
voltage, or on which the supply ground is tied to another system or equipment that can
cause ground potential to vary. It should not be used directly with supplies in which
one phase is grounded (grounded Delta).
In these cases, an isolation transformer must be installed before the drive with the
neutral of the secondary grounded to provide a balanced supply.