ABB ACH580-31, Hardware Manual

Page: 74 / 284

If the protective earth conductor is routed through a plug and socket, or similar
means of disconnection, it must not be possible to disconnect it unless power is
simultaneously removed.
Note: You can use power cable shields as grounding conductors only when their
conductivity is sufficient.
￭ Additional grounding requirements – UL (NEC)
This section gives grounding requirements according to standard UL 61800-5-1.
The protective earth conductor must be sized as specified in Article 250.122 and
table 250.122 of the National Electric Code, ANSI/NFPA 70.
For cord-connected equipment, it must not be possible to disconnect the protective
earth conductor before power is removed.
Selecting the control cables
￭
Shielding
Only use shielded control cables.
Use a double-shielded twisted pair cable for analog signals. ABB recommends this
type of cable also for the pulse encoder signals. Use one individually shielded pair
for each signal. Do not use common return for different analog signals.
A double-shielded cable (a) is the best alternative for low-voltage digital signals,
but single-shielded (b) twisted pair cable is also acceptable.
„
„
„
„
a b
￭ Signals in separate cables
Run analog and digital signals in separate, shielded cables. Do not mix 24 V DC
and 115/230 V AC signals in the same cable.
￭
Signals that can be run in the same cable
If their voltage does not exceed 48 V, relay-controlled signals can be run in the
same cables as digital input signals. The relay-controlled signals should be run as
twisted pairs.
74 Guidelines for planning the electrical installation