12
ACH550 Installation, Operation and Maintenance Manual
ACH550-UH
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:
– Frame sizes R1…R4: Remove the EM1 screw (unit is shipped with EM3
removed, see
Connection diagrams
on page
8
).
– Frame sizes R5…R6: Remove both the F1 and F2 screws (see page
9
).
• 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. Using an RFI filter grounds the input
power through the filter capacitors, which could be dangerous and could damage
the unit.
Checking motor and motor cable insulation
WARNING!
Check the motor and motor cable insulation before connecting the drive
to input power. For this test, make sure that motor cables are NOT connected to the
drive.
1. Complete motor cable connections to the motor, but NOT to the drive output
terminals (U2, V2, W2).
2. At the drive end of the motor cable, measure the insulation
resistance between each motor cable phase and Protective
Earth (PE): Apply a voltage of 1 kV DC and verify that
resistance is greater than 1 Mohm.
L1
L2
L3
PE
M
ohm
