Floating Networks - ABB ACS550-01 User Manual

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• ACS550-U1 drives are shipped with the screw removed (but included in the
conduit box).
Grounded at the
corner of the
delta
Single phase,
grounded at an
end point
EM3 (an M4x16 screw) makes an internal ground connection
that reduces electro-magnetic emission. Where EMC (electro-
magnetic compatibility) is a concern, and the network is
symmetrically grounded, EM3 may be installed. For
reference, the diagram at right illustrates a symmetrically
grounded network.

Floating Networks

Warning! Do not attempt to install or remove EM1, EM3, F1 or F2 screws while
power is applied to the drive's input terminals.
For floating networks (also known as IT, ungrounded, or impedance/resistance
grounded networks):
• Disconnect the ground connection to the internal RFI filters:
– ACS550-01, frame sizes R1...R4: Remove both the EM1 and EM3 screws
– ACS550-U1, frame sizes R1...R4: Remove the EM1 screw (unit is shipped
– Frame sizes R5...R6: Remove both the F1 and F2 screws (see page 16).
• Where EMC requirements exist, check for excessive emission propagated to
neighboring low voltage networks. In some cases, the natural suppression in
transformers and cables is sufficient. If in doubt, use a supply transformer with
static screening between the primary and secondary windings.
• Do NOT install an external RFI/EMC filter, such as one of the kits listed in "EN
61800-3 Compliant Motor Cables" on page 227. Using an RFI filter grounds the
input power through the filter capacitors, which could be dangerous and could
damage the unit.
Technical Data
Unsymmetrically Grounded Networks – EM3 Must Be Out
L1
N
(see "Power Connection Diagrams" on page 15).
with EM3 removed, see "Power Connection Diagrams" on page 15).
Grounded at the
L1
mid point of a
delta leg
L2
L3
Three phase
"Variac" without
solidly grounded
neutral
ACS550 User's Manual
L1
L2
L3
L1
L1
L2
L2
L3
L3
L1
L2
L3