Nord Drivesystems SK 530P - Individual Operation

3 Assembly and installation
BU 0630 en-2020 33
The Safe Pulse Block and the Safety Digital Input are specially designed for use with an OSSD. The
cable resistance and capacitance of the cable used must be taken into consideration.
3.3.2.1 Individual operation
Different maximum cable resistances for the Safe Pulse Block result from the rated voltage, power and
pulse frequency of the frequency inverter. The various cases are categorised into application classes:
Frequency inverter
Pulse
frequency
Application class
Rated
voltage
Size Power Types
230 V,
single-phase
Size 1 and 3
250 W …
2.2 kW
SK 5x0P-250-123 …
SK 5x0P-221-123
6 kHz
AA
16 kHz
A
400 V,
three-phase
Size 1 and 3
250 W …
2.2 kW
SK 5x0P-250-340 …
SK 5x0P-221-340
6 kHz
A
16 kHz
B
400 V,
three-phase
Size 3
3 kW … 5.5 kW
7.5 kW S3
SK 5x0P-301-340 …
SK 5x0P-551-340,
SK 5x0P-751-340-S3
6 kHz
B
16 kHz
C
The following maximum cable resistances are permissible depending on the application class:
Application class
AA A B C
R
wire,max
15 Ω 10 Ω 8 Ω 6.5 Ω
The internal resistance of the source and the resistance of the switch in an upstream OSSD must be
taken into consideration. The same values apply for the return conductor, whereby this must only carry
the currents of the Safe Pulse Block.
The following applies:


= 
…
∗


ℎ 
…
≅ 19 Ω ∗

2

 
…
= 40°
l = Cable length [km] q = Cable cross-section [mm]
ρ
cu
= Specific resistance of copper [Ω *mm
2
/km] ϑ
cu
= Cable temperature [°C]
For cable temperatures above 40°C, the specific resistance ρ
CU
must be corrected according to the
temperature coefficient α
CU
= 4*10
-3
1/K (increase by 0.4% per K).
The minimum input voltage of the protective switching device V
24V, min
for operation of the Safe Pulse
Block on an OSSD is 19.2 V. This value increases as follows depending on the maximum permissible
cable resistance:

24,
= 19.2  + 2.4  ∗



,
Information
Multiple device operation reduces the maximum
cable resistance depending on the number of
frequency inverters and the position of the frequency inverter.
The capacitance between the wires (including the shield capacitances) must not exceed a value of
C = 20 nF for each frequency inverter which is connected.