Kollmorgen 4/13/2012
Cables
S200 Position Node Installation Guide
55
APPENDIX A - CABLES
A.1 L
ONG
C
ABLES
The DC resistance of long motor power cables steals some of the available voltage when motor
current is high. The principal effect of this is some reduction in peak motor power so
acceleration and deceleration times can be longer. The cable resistance has no significant
effect on lower speed torque or top speed. For most applications, the loss of performance is
small with cables up to the maximum cable length specification. Do not operate a DC input
S200 with long cables at the lower end of the bus voltage range because too much of the
available voltage is lost by the cable resistance. For AC input S200s, the DC resistance of the
motor power cable is rarely an issue because the voltage drop across the resistance is usually
a small fraction of the available nominal bus voltage.
For DC S200 applications with long cables and demanding dynamics, the 14 AWG cable is
preferred over the 18 AWG cable. Cable voltage drop vs cable length is shown in the table
below.
Cable Voltage Drop vs Length
V
LOSS
in cable as
a percent of 75 V bus
Cable
Length
(meter)
2 x Rphase
(ohm)
V line-line peak
at 0.866 x 18 A
RMS
18 AWG cable
18 cable
14 cable
3
0.126
2.77
3.7 %
1.5 %
10
0.413
9.09
12.1 %
4.8 %
25
1.03
22.7
30.3 %
12.0 %
50
(50 m not recommended with 6/18 A
RMS
) N/A
24.0
%
A.2 C
USTOM
C
OMPOSITE
C
ABLES
A composite cable has both feedback and power wires in one cable. One of the critical
requirements for a composite cable is to provide a high degree of isolation between the power
and feedback wires. For 240 VAC-connected drives, the power wires can have up to 400 V
peak-
peak
fast switching PWM waveforms that can couple to the feedback wiring, causing
communication errors between the Drive and the Smart Feedback Device (SFD).
Kollmorgen has developed and sells a composite cable that has very good isolation between
the power and feedback sections. It is strongly recommended that this raw cable be used for
custom composite cable designs. Contact your Kollmorgen sales representative for additional
information. If this cable does not meet your specifications, the following are some guidelines
for custom composite cable development.
Due to the complexity of modeling and
understanding cable coupling, a new composite cable needs to be prototyped and tested
to have confidence that it will be reliable.
1)
Composite cable should have double concentric feedback shields – one shield within
another.
The raw composite cable that has been tested and is known to work well with the S200 has the
following structure:
double, concentric shields
around the feedback wires plus an outer shield
around the whole cable (see diagram below). This type of raw cable is strongly recommended.
Testing shows double, concentric, shielding is ten times better than single shielding at reducing
coupling from the power wires to the feedback data wires.
