NORD Drivesystems BU0510 User Manual
Page 24
POSICON position control for NORD frequency inverters, SK 530E and above
24
Subject to technical alterations
BU 0510 GB-3911
3.2.2.1
Supplementary settings - SSI absolute encoders
Protocol settings for SSI encoders are made in parameter P617.
In detail, this defines:
the format in which the positions are transferred (binary / Gray code),
whether a loss of voltage to the encoder is communicated to the FI ("Power Fail Bit") and
whether the encoder supports the communication version "Multiply Transmit" for which the position is
communicated a second time in a mirrored form in order to improve the reliability of the transfer.
3.2.2.2
Supplementary settings - CANopen absolute encoders
The baud rate and the CAN address must be set on the encoder. For the assignment of the switches on the
encoder, please refer to the manufacturer´s operating instructions.
The CAN address for the absolute encoder should be set in parameter P515 "CAN Address" according to the
following formula:
Encoder CAN address = Inverter CAN address (P515[-01] ) + 1
The CAN baud rate set in the encoder must be identical to the parameter P514 "CAN Baud Rate" and all other
participants in the bus system.
If parameterisation of the encoder is carried out via the frequency inverter, the transmission cycle for the
absolute encoder position is simultaneously set via the baud rate.
For the operation of several CANopen absolute encoders on a bus system, e.g. for synchronous operation,
different transmission cycle times can be set for the CAN master and the CANopen absolute encoders.
With the parameter P552 "CAN Cycle Time" the cycle time for the system bus master mode can be
parameterised in Array [-01 and for the CANopen absolute encoder in Array [-02]. Care must be taken that the
parameterised values are not lower than the values in the column for the minimum values of the actual cycle
time. This value depends on the baud rate set in parameter P514 "CAN Baud Rate".
P514
Baud rate
[kBaud]
P552 [
-
01]
Default CAN
Master
[ms]
P552 [
-
02]
Default CANopen
Absolute encoder
[ms]
P552 [
-
02]
Minimum value for
actual cycle time
[ms]
Bus load caused by
an encoder
[%]
10
50
20
10
42.5
20
25
20
10
21.2
50
10
10
5
17.0
100
5
5
2
17.0
125
5
5
2
13.6
250
5
2
1
17.0
500
5
2
1
8.5
1000
1
5
2
1
4.25
Table 13: Encoder cycle time dependent on the baud rate
The possible bus load in the system always depends on the real-time specific to the system. Very good results
are achieved with a bus load less than 40%. Under no circumstances should a bus load greater than 80% be
selected. For the estimation of the bus load, the other possible bus traffic (setpoint and actual values for the
FIs and other bus participants) should also be taken into account.
Additional explanations about the CAN interface can be obtained from Manual BU 0060.
1
Only for testing purposes. Reliable operation is not guaranteed.