NORD Drivesystems BU0570 - Manual (Page 23)

4 Communication
BU 0570 GB-0312 Subject to technical amendments 23
4.2.5 Setpoint and actual values
The meanings of setpoints are defined via the FI parameters P546 to P548 (SK 540E and above:
P546[-01] … [-05]). For the actual values, this determination is made via the FI parameters P543 to P545
(SK 540E and above: P543[-01] … [-05]).
The transfer of setpoint and actual values is carried out by three different methods, which will be explained
below.
Percentage transfer
The process value is transferred as a whole number with a value range of -32768 to 32767 (8000 hex to
7FFF hex). The value 16384 (4000 hex) is equal to 100%. The value -16384 (C000 hex) is equal to -100%.
For frequencies, the 100% value corresponds to the FI parameter "Maximum Frequency" (P105) and for
currents, this is the FI parameter "Torque Current Limit" (P112) Frequencies and currents result from the
following formulae.
16384
105 P Value
Frequency


16384
112 P Value
Current


Value = the 16Bit actual or setpoint value transmitted via Ethernet
Formula 1 Formation of 16Bit setpoint/actual value
Binary transmission
Inputs and outputs as well as Digital In bits and Bus Out bits are evaluated for each bit.
Transmission of positions
In the FI, positions have a value range of +/- 50000,000 rotations. A motor rotation can be divided into a
maximum of 1000 steps. This scaling is independent of the encoder which is used.
The 32Bit value range is divided into a Low and a High word, so that 2 setpoint/actual values are required
for transmission.
Direction of
transmission
Transmitted data (8 Byte)
1. word 2. word 3. word 4. word
... to SK TU3- Control word 32Bit setpoint Setpoint 3
... from the SK TU3- Status word Actual value 1 32Bit actual value
Table 16 Depiction of 32Bit setpoint/actual values
It is also possible to only transmit the Low component of the position. This results in a limited value range
from +32,767 to -32,768 rotations. This value range can be extended with the aid of the gear ratio factor
(P607 & P608). However, it must be noted that there is an according reduction in the resolution.