Installation manual
PSC1-C-10 Installation manual V2.6
Page 66 of 173
Version: 57E
4.3.3
Permissible capacitive and inductive load on safe outputs
The safe outputs on the PSC1 are of an OSSD character. I.e. the outputs are shut down cyclically to test
the shutdown capability and the status read back.
The test on the shutdown capability is based on the following criteria / functions:
-
After the shutdown of the output, the output voltage is allowed to be max. 5.6 V
-
The permissible voltage must be reached at the latest after 400 µs
-
If the permissible voltage is reached, the test is considered successful, the output is re-
activated without any further delay
-
If the permissible voltage has still not been reached after 400 µs, an alarm is triggered and all
safe outputs (second channel for safe outputs!) are deactivated
The illustration shows below the ideal (green) and typical (red) curves.
To determine the maximum permissible capacitance or inductance, the time constant
of the actual
RC or RL element on the output is to be considered.
This RC or RL element defines the actual discharge curve:
The voltage of max. 5.6 V is reliably achieved after 3
.
Therefore:
3
< 350µs
< 100µs
With the relationship
it is possible to determine the max. capacitive or inductive load that can be used in conjunction with
the related ohmic load:
or
Typical values for the capacitance C are C=20 nF and for the series inductance L = 100 mH
= RC =
L
R
L
max
=
*
R = 10
-4
*
R
Ideal curve
Actual curve
Switching threshold
2
3
4
Max. 400 µs
C
max
= =
R
10
-4
R
