Wiring Precautions - ABB ACS255 User Manual

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5.1.2. Grounding Guidelines
The ground terminal of each ACS255 should be individually connected DIRECTLY to the site ground bus bar (through the filter if installed).
ACS255 ground connections should not loop from one drive to another, or to, or from any other equipment. Ground loop impedance must
confirm to local industrial safety regulations. To meet UL regulations, UL approved ring crimp terminals should be used for all ground wiring
connections.
The drive Safety Ground must be connected to system ground. Ground impedance must conform to the requirements of national and local
industrial safety regulations and/or electrical codes. The integrity of all ground connections should be checked periodically.
5.1.3. Protective Earth Conductor
The Cross sectional area of the PE Conductor must be at least equal to that of the incoming supply conductor.
5.1.4. Safety Ground
This is the safety ground for the drive that is required by code. One of these points must be connected to adjacent building steel (girder, joist),
a floor ground rod, or bus bar. Grounding points must comply with national and local industrial safety regulations and/or electrical codes.
The safety ground terminal provides a grounding point for the motor cable shield. The motor cable shield connected to this terminal (drive
end) should also be connected to the motor frame (motor end). Use a shield terminating or EMI clamp to connect the shield to the safety
ground terminal.
5.1.5. Motor Ground
The motor ground must be connected to one of the ground terminals on the drive.
5.1.6. Ground Fault Monitoring
As with all inverters, a leakage current to earth can exist. The ACS255 is designed to produce the minimum possible leakage current while
complying with worldwide standards. The level of current is affected by motor cable length and type, the effective switching frequency, the
earth connections used and the type of RFI filter installed. If a GFCI (Ground Fault Current interrupter) is to be used, the following conditions
apply: -

The device must be suitable for protecting equipment with a DC component in the leakage current

Individual GFCI's should be used for each ACS255
The ACS255 product range has input supply voltage surge suppression components fitted to protect the drive from line voltage transients,
typically originating from lightning strikes or switching of high power equipment on the same supply.

5.2. Wiring Precautions

Connect the ACS255 according to sections 5.3 and 5.4, ensuring that motor terminal box connections are correct. There are two connections in
general: Star and Delta. It is essential to ensure that the motor is connected in accordance with the voltage at which it will be operated. For
more information, refer to section 5.5.
Type MC continuous corrugated aluminium armor cable with symmetrical grounds or shielded power cable is recommended for the motor
cables if metallic conduit is not used.
The power cables must be rated for 75˚C (167˚F).
5.2.1. EMC Filters
WARNING! EMC filters should not be used when there is a risk that the phase to earth voltage could exceed the phase to
phase voltage, Typically IT (ungrounded) and corner-grounded TN systems, otherwise this may cause danger or damage to
the EMC filter.