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60 Planning the electrical installation
Selecting the power cables
General rules
Dimension the mains (input power) and motor cables according to local regulations:
•
The cable must be able to carry the drive load current. See
(page 119) for the rated currents.
•
The cable must be rated for at least 70
temperature of conductor in continuous use. For US, see
requirements
(page 62).
•
The inductance and impedance of the PE conductor/cable (grounding wire)
must be rated according to permissible touch voltage appearing under fault
conditions (so that the fault point voltage does not increase excessively when a
ground fault occurs).
•
600 V AC cable is accepted for up to 500 V AC. 750 V AC cable is accepted for up
to 600 V AC. For 690 V AC rated equipment, the rated voltage between the
conductors of the cable should be at least 1 kV.
For drive frame size R5 and larger, or motors larger than 30 kW (40 hp), symmetrical
shielded motor cable must be used (figure below). A four-conductor system can be
used up to frame size R4 with up to 30 kW (40 hp) motors, but shielded symmetrical
motor cable is recommended.
WARNING! Do not use unshielded single-core supply cables in IT
(ungrounded) networks. A dangerous voltage can become present on the
non-conductive outer sheath of the cable. This can cause injury or death.
Note: When continuous conduit is employed, shielded cable is not required.
A four-conductor system is allowed for input cabling, but shielded symmetrical cable
is recommended. To operate as a protective conductor, the shield conductivity must
be as follows when the protective conductor is made of the same metal as the phase
conductors:
Cross-sectional area of the phase
conductors
Compared to a four-conductor system, the use of symmetrical shielded cable
reduces electromagnetic emission of the whole drive system as well as motor
bearing currents and wear.
The motor cable and its PE pigtail (twisted shield) should be kept as short as
possible in order to reduce electromagnetic emission.
Longer cables cause a motor voltage decrease which limits the available motor
power. The decrease depends on the motor cable length and characteristics.
Contact ABB for more information. Note that a sine filter (optional) at the drive
output also causes a voltage decrease.
2
S (mm
)
S < 16
16 < S < 35
35 < S
°
°
C (158
F) maximum permissible
Additional US
Minimum cross-sectional area of the
corresponding protective conductor
2
S
(mm
p
S
16
S/2
Technical data
)
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