Installation
Electrical installation
Bus cable length
5
l
29
EDSMF2178IB EN 3.0
5.2.5.3 Checking the use of repeaters
Compare the values derived from Tab. 5−1 Total cable length (¶ 27) and Tab. 5−2 Segment
cable length (¶ 28).
ƒ If the sum of the segment cable lengths is smaller than the total cable length to be
implemented, either repeaters must be used or the cable cross−section must be
increased.
ƒ If the use of repeaters reduces the max. possible total cable length so much that it is
smaller than the total cable length to be implemented, then the cable cross−section
must be increased or less repeaters must be used or the baud rate must be
decreased.
ƒ The use of a further repeater is recommended as ...
– service interface
Advantage: Trouble−free connection during bus operation is possible.
– calibration interface
Advantage: The calibration/programming unit remains electrically isolated.
Example
Given
Total cable length to be implemented 450 m
Number of nodes 32
Cable cross−section 0.50 mm
2
(AWG 20)
Baud rate 125 kbps
Repeater used Lenze repeater EMF2176IB
Reduction of the max. total cable length per
repeater (EMF2176IB)
30 m
Results
Max. total cable length 630 m
(see Tab. 5−1 Total cable length (^ 27))
Max. segment cable length 360 m
(see Tab. 5−2 Segment cable length (^ 28))
Comparison The max. segment cable length is smaller than the total cable
length to be implemented.
Conclusion A repeater must be installed at the determined max. segment
cable length of 360 m.
Results with 1 repeater
Max. total cable length 600 m
(Reduction of the total cable length (^ 27) by 30 m)
Max. segment cable length 720 m
Comparison Both the possible total cable length and the segment cable lengths
are larger than the total cable length to be implemented.
Conclusion 1 repeater is sufficient to implement the total cable length of 450
m.
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