Cables 4/13/2012
Kollmorgen
56
S200 Position Node Installation Guide
Outer Shield
Motor Connector Shield
Motor W ires
Drain W ire
PE W ire
Feedback
Outer Shield
(Connect to SFD Shell)
Feedback
Inner Shield
(Connect to Logic GND)
SFD Comm unication
twisted pair
Optional Foil Shield Shield
SFD Return
(Inner Drain W ire
and inner shield)
SFD +5 VDC
Outer Jacket
Jacket
Inner Jacket
Composite Cable Cross-Section
There can be substantial capacitance between the power wires and adjacent feedback shield in
a composite cable. Some of the PWM ampere level spikes tend to return in this adjacent shield.
In effect, the power stage voltage and current
drive
the feedback shield nearest to the power
wires. In a single-shielded feedback cable this
driven
shield is also around the feedback data
wires, so some coupling can occur. With double, concentric feedback shields, the
driven
shield
is the outer of the two feedback shields, and interposed between the
driven
shield and
feedback data wires is the inner feedback shield. Typically, the inner feedback shield is isolated
from the connector shells and connected to the return for the power supply powering the
feedback device.
NOTE
A raw cable with two pairs of twisted, shielded feedback sections inside a composite cable
is electrically the same as single feedback shielding. There may physically be two feedback
shields in such a cable, but these shields are not concentric. There is only one shield
between the power wires and feedback wires, where with double, concentric feedback
shields, there are two.
2)
SFD +5 and Gnd Resistance Spec
To insure that the SFD + 5 voltage at the SFD inside the motor is within specification, the
voltage drop total in the SFD + 5 V wire and SFD + 5 V RTN wire must not be greater than 0.5
V at 150 mA. For this reason, a cable requirement is that the total resistance of the feedback
SFD + 5 V wire plus SFD + 5 V RTN wire must be < 3.33
Ω
(at 20° C). In practice, this means
that for long cables, the AWG wire gage needs to be considered.
NOTE
The inner shield of the a double, concentric feedback cable, when isolated from the
terminating connector shells, can also function as a conductor to carry some or all of the
SFD + 5 V RTN current. This is useful to keep the total SFD + 5 and RTN resistance within
specification on long cables without having large diameters.
3) Feedback Characteristic Impedance
Kollmorgen's S200 feedback cables are designed to have a feedback data pair differential
impedance of 81
Ω
(at 1 MHz). Impedances in the range of 50 to 100
Ω
, while not tested, will
likely work properly with the S200.
Purchase a Kollmorgen-built composite feedback cable, review its construction, and test its
performance. There are many ways to connect the multiple shields of a composite cable. A
good way to understand how the Kollmorgen composite cable is built is to buy a short
Kollmorgen S200 composite cable, open it up, and see how the shields at both the motor and
drive end are connected.
