Wiring Precautions; Incoming Power Connection - 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).
The 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.
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
5.1.7. Shield Termination (Cable Screen)
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.

5.2. Wiring Precautions

Connect the ACS255 according to section 5.9, 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 5.6 Motor Terminal Box Connections.
Type MC continuous corrugated aluminium armour 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).

5.3. Incoming Power Connection


Power should be connected to L1, L2, and L3. Phase sequence is not important.

For compliance with CE and C Tick EMC requirements, a symmetrical shielded cable is recommended.

For compliance with CSA requirements, transient surge suppression shall be installed on the line side of this equipment and shall be
rated 600V (phase to ground), 600V (phase to phase), suitable for overvoltage category III, and shall provide protection for a rated
impulse withstand voltage peak of 4 kV or equivalent.

A fixed installation is required according to IEC61800-5-1 with a suitable disconnecting device installed between the ACS255 and the AC
Power Source. The disconnecting device must conform to the local safety code / regulations (e.g. within Europe, EN60204-1, Safety of
machinery).

The cables should be dimensioned according to any local codes or regulations. Guideline dimensions are given in section 11.2.

Suitable fuses to provide wiring protection of the input power cable should be installed in the incoming supply line, according to the
data in section 11.2. The fuses must comply with any local codes or regulations in place. In general, type gG (IEC 60269) or UL type T
fuses are suitable; however in some cases type aR fuses may be required. The operating time of the fuses must be below 0.5 seconds.

When the power supply is removed from the drive, a minimum of 30 seconds should be allowed before re-applying the power. A
minimum of 5 minutes should be allowed before removing the terminal covers or connection.

The maximum permissible short circuit current at the ACS255 Power terminals as defined in IEC60439-1 is 100kA.

An optional Input Choke is recommended to be installed in the supply line for drives where any of the following conditions occur:-
o
The incoming supply impedance is low or the fault level / short circuit current is high.
o
If the transformer kVA rating is more than 10x the kVA rating of the drive or ensure that the per drive source
impedance is less than 0.5%
o
The supply is prone to dips or brown outs
o
An imbalance exists on the supply (3 phase drives)
o
The power supply to the drive is via a busbar and brush gear system (typically overhead Cranes).

In all other installations, an input choke is recommended to ensure protection of the drive against power supply faults.