Safety technology basics
102597_en_03 PHOENIX CONTACT 23 / 136
Example For an emergency stop application with the PSR-ESAM4 (see Figure 3-2), the following cal-
culations can be made:
Assumed values Cable cross section: A = 1.5 mm²
Electrical conductivity of copper (Cu): = 56 m/( x mm²) (at 20 °C)
Technical data for the
safety relay
Input data:
Maximum voltage drop for S11-S12, S21-S22, and S33-S34: approximately 2 V DC (corre-
sponds to approximately 50 = RL)
RL = R1 + R2 + R3
RL = 50
Calculated value l = RL x A x
l = 50 x 1.5 mm² x 56 m/( x mm²)
l = 4200 m
Where:
This refers to the forward and return line for both channels in the enable circuit and reset
circuit (S11-S12, S21-S22, and S12-S34).
The specified values can be found in the data sheet for the corresponding safety relay.
l Permissible cable length
R
L
Cable resistance
A Cable cross section
(Kappa) Electrical conductivity of copper (Cu)
If the application is operated with autostart, the cable lengths between S12-S35 can be
disregarded.
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