
2.SPECIFICATIONS SPECIFICATIONS B-65382EN/02
- 72 -
2.5.8 Cable Length Design
Design the cable length so that the voltage drop by cables K2 and K4
and that by cables K2 and K5 are 0.2 V or less.
NOTE
When designing the cable length, note that the sum
of the current consumption of the position detection
circuit, magnetic pole sensor, and linear encoder in
a linear motor flows through cable K2.
Sample calculations
When HEIDENHAIN LS486 is used and the length of cable K2 is
determined to be 10 m by design:
- Linear encoder LS486 (Maximum current consumption: 0.15 A)
- Position detection circuit A860-0333-T201
(Maximum current consumption: 0.25 A)
- Magnetic pole sensor A860-0331-T001
(Maximum current consumption: 0.05 A)
- Conductor resistance of a copper wire with a nominal cross
section of 0.5 mm
2
at 20°C: 38.7 × 10
-3
Ω/m
<1> Voltage drop by cable K2: Vd (V)
When three copper wires having a nominal cross section of 0.5
mm
2
are connected, the voltage drop is:
Vd=(0.25+0.05+0.15) × {(38.7×10
-3
÷3) × (10×2)} 0.116(V)
according to V = I × R.
* (10×2) in the expression means both ways between 5 and 0 V.
<2> Maximum length of cable K4: L1 (m)
To suppress the voltage drop to 0.2 V or less, the cable length
must be designed so that the voltage drop by cable K4 is 0.084 V
or less.
When two copper wires having a nominal cross section of 0.5
mm
2
are connected, the maximum cable length is:
L1=[{(0.2-0.116) ÷0.05}÷ (38.7×10
-3
÷2)] ÷2 43.4m
according to conductor length (m) = resistance (Ω) ÷ conductor
resistance (Ω/m).
<3> Maximum length of cable K5: L2 (m)
L2=[{(0.2-0.116) ÷0.15} ÷38.7×10
-3
] ÷2 7.2m
NOTE
The standard LS486 cable uses two copper wires
having a nominal cross section of 0.25 mm
2
for
connecting each of 5 and 0 V. At this time, the
conductor resistance of the wires is 38.7 × 10
-3
Ω/m.