Emerson Digitax ST User Manual page 32

Safety Product Mechanical
Information information installation
If any of the digital inputs or outputs (including the drive
enable input) are connected in parallel with an inductive load
(i.e. contactor or motor brake) then suitable suppression (i.e.
diode or varistor) should be used on the coil of the load. If no
CAUTION suppression is used then over voltage spikes can cause
damage to the digital inputs and outputs on the drive.
Ensure the logic sense is correct for the control circuit to be
used. Incorrect logic sense could cause the motor to be
started unexpectedly.
Positive logic is the default state for the drive.
CAUTION
N
NOTE
Any signal cables which are carried inside the motor cable (i.e. motor
thermistor, motor brake) will pick up large pulse currents via the cable
capacitance. The shield of these signal cables must be connected to
ground close to the point of exit of the motor cable, to avoid this noise
current spreading through the control system.
N
NOTE
The SAFE TORQUE OFF drive enable terminal is a positive logic input
only. It is not affected by the setting of Pr 8.29 Positive logic select.
N
NOTE
The common 0V from analog signals should, wherever possible, not be
connected to the same 0V terminal as the common 0V from digital
signals. Terminals 3 and 11 should be used for connecting the 0V
common of analog signals and terminals 21, 23 and 30 for digital
signals. This is to prevent small voltage drops in the terminal
connections causing inaccuracies in the analog signals.
32
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