Safe Torque Off (STO) with PSD1
68 (109)
192-011006N8 2019-07
09.10.19 09:27
Stop-
Category
Safety
function
Requirement
System
Behaviour
Remark
0
Safe Torque
Off (STO)
Stopping by immediately
switching off the energy
supply of the machine
drive elements
Uncontrolled
stop
Uncontrolled stop is the stopping of a machine
movement by switching off the energy of the
machine drive elements.
Available brakes and/or other mechanical
stopping components are applied.
1
Safe stop 1
(SS1)
Stop where the energy of
the machine drive
elements is maintained in
order to reach a stop. The
energy supply is only
interrupted, if the
standstill is attained.
Controlled
stop
Controlled stop is the stopping of a machine
movement by for instance resetting the
electrical command signal to zero, as soon as
the stop signal has been detected by the
controller, the electrical energy for the machine
drive elements remains however during the
stopping procedure.
2
Safe stop 2
(SS2)
Stop where the energy to
the machine drive
elements is maintained.
Controlled
stop
This category is not covered.
6.1.2.
Applications in accordance with the regulations
The Servo Drive PSD supports the "safe torque off" (STO) safety function, with
protection against unexpected startup according to the requirements of EN ISO
13849-1, category 3 to PLe and EN 14118.
Together with the external safety control device, the "safe stop 1" (SS1) safety
function according to the requirements of DIN EN 61800-5-2:2008 category 3 can
be used. As the function is however realized with the aid of an individually settable
time delay on the safety control, it must be taken into account that, due to an error
in the drive system during the active braking phase, the motor coasts uncontrolled
or may even accelerate actively in the worst case until the expiry of the preset
switch-off time.
A risk evaluation which must be carried out according to the machine standard
2006/42/EG resp. EN ISO 12100 and EN ISO 13849-1, the machine manufacturer
must project the safety system for the entire machine including all integrated
components. This does also include the electrical drives.
6.1.3.
Qualified Personnel
Planning, installation and initial system commissioning require a detailed
understanding of this description.
Standards and accident prevention regulation associated with the application must
be known and respected as well as risks, protective and emergency measures.
The implementation of the safety functions as well as maintenance and service can
only be carried out by suitably qualified personnel with many years of experience in
the field of machine safety with drives.
We assume that these specialists have a good knowledge of English.
In the case of deviating regulations (in particular work by persons who do not
speak English), the machine manufacturer must provide these persons with the
necessary information in the national language.
