BECKHOFF AX2500 - Manual (Page 68)

8.18 Fieldbus connection
8.18.1 CANopen interface (X7)
The interface for connection to the CAN bus (default: 500 kbps). The master is fitted with
a CAN input. All axis modules in the system are connected to this through the internal
bus. The last axis module has a CAN output, where the CAN bus either continues to
other bus participants or is terminated by a termination resistor.
The integrated profile is based on the communication profile CANopen DS301 and the
drive profile DS402. The following functions are available in connection with the inte-
grated position controller: Jogging with variable speed, homing, start motion task, start
direct task, digital setpoint provision, data transmission functions and many others.
Detailed information can be found in the CANopen manual.
The interface is at the same potential as the internal logic, and uses AGND as the ground
reference.
AGND must be connected to the control system ground for potential equalization!
CAN bus cable
To meet ISO 11898 you should use a bus cable with a 120
W characteristic impedance.
The maximum usable cable length for reliable communication decreases with increasing
transmission speed. As a guide, you can use the following values which we have mea-
sured, but they must not be assumed to be limits:
Cable data: Characteristic impedance
100-120
W
Cable capacitance max. 60 nF/km
Conductor loop resistance 159.8 W/km
Cable length, depending on the transmission rate
Transmission rate / kbps max. cable length / m
1000 20
500 70
250 115
Lower cable capacitance (max. 30 nF/km) and lower lead resistance (loop: 115
W/km)
make it possible to transmit over longer distances.
(Characteristic impedance 150 ± 5
W Þ terminating resistance 150 ± 5 W).
For EMC reasons, the SubD connector housing must fulfill the following conditions:
— metal or metallized housing
— provision for connecting the cable shielding within the housing,
large-area connections
68 AX2500 Product Manual
Electrical Installation
06/2007
BECKHOFF
AX2500