Grounding
3-7
Cable Shields
Motor and Input Cables
Shields of motor and input cables must be bonded at both ends to provide a
continuous path for common mode noise current.
Control and Signal Cables
Shields of control cables should be connected at one end only. The other
end should be cut back and insulated.
–
The shield for a cable from one cabinet to another must be connected
at the cabinet that contains the signal source.
–
The shield for a cable from a cabinet to an external device must be
connected at the cabinet end, unless specified by the manufacturer of
the external device.
Never connect a shield to the common side of a logic circuit (this will
introduce noise into the logic circuit). Connect the shield directly to a
chassis ground.
Shield Splicing
Figure 3.5 Spliced Cable Using Shieldhead Connector
If the shielded cable needs to be stripped, it should be
stripped back as little as possible to ensure that continuity
of the shield is not interrupted. Avoid splicing motor
power cables when ever possible. Ideally, motor cables
should run continuously between the drive and motor
terminals. The most common reason for interrupted cable/
shield is to incorporate an “at the motor” disconnect
switch. In these cases, the preferred method of splicing is
to use fully shielded bulkhead connectors.
Single Point
A single safety ground point or ground bus bar should be
directly connected to the building steel for cabinet
installations. All circuits including the AC input ground
conductor should be grounded independently and directly
to this point/bar.
Isolated Inputs
If the drive’s analog inputs are from isolated devices and the output signal is
not referenced to the ground, the drive’s inputs do not need to be isolated.
An isolated input is recommended to reduce the possibility of induced noise
if the transducer’s signal is referenced to ground and the ground potentials
are varied (Refer to
Noise Related Grounds on page 3-3
). An external
isolator can be installed if the drive does not provide input isolation.
PE
Summary of Contents for Allen-Bradley 1305-AA02A
Page 4: ...ii Summary of Changes Notes ...
Page 40: ...2 18 Power Distribution Notes ...
Page 48: ...3 8 Grounding Notes ...
Page 68: ...4 20 Practices Notes ...
Page 78: ...6 8 Electromagnetic Interference Notes ...
Page 94: ...Glossary 4 UL Underwriters Laboratories ...
Page 100: ...Index 6 ...
Page 101: ......
