ABB TB852 3BSC950263R1 terminal unit
Figure 3-4 The NTAC-02 Pulse Encoder Interface Module: terminaldesignations.
Current Consumption The NTAC-02 has to be supplied with 24 V d.c. power, either from the
NIOC board (max. 250 mA), or an external power supply. As the
current consumption of the module depends on many factors (e.g.
max. speed of the motor, encoder pulse number per revolution,
encoder cable length and leakage capacitance), it should be checked
on each occasion if an additional power supply is needed.
The approximate current consumption of the NTAC-02 can be read
from the chart or calculated with the formula in Figure 3-5.
Figure 3-5 The current consumption of the NTAC-02 for four different
encoder cable lengths. The chart is based on a measurement with a
1024 ppr pulse encoder with differential outputs coupled to a motor
shaft rotating at 1500 rpm.
Cabling The pulse encoder should be connected to the NTAC module with a
cable specified below.
Either a single-ended or differential connection can be used, but the
manufacturer’s recommendations should be taken into account. On
pages 3-8 to 3-10, there are wiring diagrams for different encoder
output types. Compare encoder documentation and the following figure
to determine the output type.
Note: The cable screens should be earthed at the NTAC module only.
Note: Do not route the encoder cables parallel to power cables.
Cable construction 4 × (2+1)
Twisted pair cable with individual and overall screens.
Conductor cross sectional area 0.5 to 1.0 mm2
Maximum length
Dependent on encoder output type as follows:
300 m (differential push-pull)
200 m (single-ended push-pull)
100 m (open collector or emitter)

When the encoder is connected correctly, running the drive in the
Forward (positive) direction should produce positive encoder feedback.
On incremental encoders, the two output channels, usually marked
1 and 2 or A and B, are 90° (electrical) apart from each other. When
rotated clockwise, most encoders – but not all – have channel 1 leading
channel 2 as illustrated below. Determine the leading channel by
referring to the encoder documentation, or by measuring with an
oscilloscope.
The encoder output channel that leads when the drive runs Forward
should be connected to NTAC input A, the output channel that trails to
NTAC input B.
The zero reference output channel (usually marked 0, N or Z) needs to
be connected in positioning applications only.
Figure 3-8 Connection diagram for pulse encoders with open emitter
(sourcing) outputs.
Programming The NTAC-02 is programmed through drive parameters. After the
communication between the module and the drive is activated, several
parameters are copied to the drive. These parameters must be
checked and adjusted. For further information, see the Firmware
Manual, Parameter Groups 98 and 50.
Note: The new settings take effect only the next time the module is
powered up.
NTAC Module
Replacement
The NTAC-01 and NTAC-02 are not interchangeable. A faulty NTAC
module must be replaced with a spare part of the same type.
For reference, the differences between the NTAC-01 and NTAC-02
modules are detailed in Appendix C.