7.15.2 Use as directed
The STO function is exclusively intended to provide a functional safe torque off of the motion
system. To achieve this functional safety, the wiring of the safety circuits must meet the
safety requirements of IEC 60204, ISO 12100 and ISO 13849.
If the global STO function is in use, then the inputs STO-Enable 1/2 must be connected to the
exit of a safety control or a safety relay, which at least meets the requirements of PLd, CAT 3
according to ISO 13849.
The 24 VDC supply unit for local STO supply must accord to PELV (EN 60204-1) require-
ments.
7.15.3 Prohibited use
The STO function must not be used if the drive is to be made inactive for the following reas-
ons:
Cleaning, maintenance and repair operations, long inoperative periods. In such cases, the
entire system should be disconnected from the supply and secured (main switch).
Emergency-Off situations. In an Emergency-Off situation, the main contactor is switched
off (by the Emergency-Off button).
Wiring the system with hybrid cables from other manufacturers than Kollmorgen is not
allowed.
Changing cables or connectors is not allowed.
Do not use STO Status signals for functional safety.
7.15.4 Safety characteristic data
The systems are described with the following characteristic data:
Structure
STO
ISO
13849-1
MTTF
d
IEC
62061
PFH
[1/h]
SFF
[%]
T
M
[Years]
AKD-C + 1 x AKD-N
global PL d, CAT 3
≥ 100
SIL 2
2.9E-08 97.08
20
AKD-C + 8 x AKD-N
global PL d, CAT 3
≥ 100
SIL 2
2.9E-08 99.44
20
1 x AKD-N-DS/DT
local
PL d, CAT 3
≥ 100
SIL 2
2.9E-08 97.12
20
A very unlikely but possible event can happen, if within a very short time 2 not adjacent
IGBTs will have a short circuit. In such case a movement of a maximum angle of 120° (elec-
trical) can happen. This effect can only happen if the drive is in the function STO. If the total
failure rate of the IGBT is 120 FIT normally for such short circuit 60 FIT will be valid (50:50
model). By such event 2 specific IGBTs have to fail at same time. The calculation shows a
probability of 1.5 * 10
-15
per hour (without common cause failure). Even if the STO function
will be issued for a whole year, this event will only happen every 100 Billion years.
7.15.5 Response Time
The delay from falling edge at global STO Enable input until energy supply to the motor is
interrupted, depends on the number of connected AKD-N to the string. Maximum reaction
time is 10 ms. The more AKD-N are connected to the string, the shorter is the reaction time.
AKD-C Installation | 7 Technical description and data
Kollmorgen | kdn.kollmorgen.com | February 2018
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