Siemens SINAMICS G180 Installation And Operating Instructions Manual page 163

Digital inputs -X2:27 and -X2:28 as PTC thermistor inputs
The digital inputs are interpreted as a normal digital input for control with a 24 V signal. If
these control cable terminals are wired to 10 V potential using a PTC thermistor sensor,
these function automatically as PTC thermistor monitoring inputs. The selection bits "PTC
X2:27" and "PTC X2:28" indicate the PTC thermistor status. To do this it is mandatory that
you set parameter "P-PULSE INPUT/Mode = inactive".
NOTICE
Unsuitable evaluation unit
If the PTC thermistor for explosion proof motors or for safe isolation is not evaluated using
an ATEX-certified, safely isolated evaluation unit or the peripherals board, damage to the
converter can occur.
Use an ATEX-certified, safely isolated evaluation unit or the peripherals board for safe
operation.
Digital inputs -X2:27, -X2:28 and -X2:29 as frequency or tachometer inputs
These digital inputs can be used as a frequency or tachometer input, for example, in the
following way.
● The field-oriented control at input -X25 / -X101 is not possible, e.g. if the n-sensor is
installed on the machine and there is a gearbox between machine and motor.
● Only one simple proximity switch with e.g. four impulses per revolution is available. The
resolution for the field-oriented regulation is too small in this case. It is suitable for
displays or more precise speed regulation.
● You connect a frequency-dependent setpoint generator of the type used for mining
applications, for example.
Example applications for the digital inputs as frequency inputs:
● Proximity switch with NAMUR output or with PNP-3 wire output
● Two-channel digital tachometer with HTL output
In order that you can use these inputs as frequency or tachometer input, you must select the
required evaluation function using parameter "P-PULSE INPUT/Mode". Independent of the
selected evaluation function, as a result, inputs -X2:27 to :29 are assigned, and are no
longer available as digital inputs. The digital input bits in the bit pool X2:27, X2:28 and X2:29
are connected to a fixed value of "0". Likewise, the bits in the bit pool for the PTC evaluation
"PTC X2:27" and "PTC X2:28" are connected to 0. These can no longer be used.
Possible warnings and faults that are obtained that can be parameterized, for example
"MotorWindingTemp." must be resolved by making the appropriate parameter change, e.g.
setting to "inactive".
Installation and Operating Instructions SINAMICS G180
Operating Instructions, 02/2019, 4BS0751-007
Operation
8.5 Special functions
161