Festo CMMT-ST-C8-1C-...-S0 Series User manual

CMMT-ST-C8-1C-...-S0
Servo drive
Manual | Safety
sub-function | STO,
SS1-t
8154451
2021-04b
[8154453]

Translation of the original instructions
ET 200®, PNOZ®, Pilz®, SIEMENS®, ET 200SP® are registered trademarks of the respective trademark
owners in certain countries.

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Table of contents
1 About this document. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Target group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Applicable documents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Product version. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Product labelling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 Specified standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Safety Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Intended use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.1 Range of application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.2 Permissible components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Foreseeable Misuse. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4 Training of qualified personnel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.5 CE marking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.6 Safety engineering approval. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3Additional information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4 Product overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Safety sub-functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1.1 Function and application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1.2 Safety sub-function STO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1.3 Safety sub-function SS1-t. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1.4 Cross-wiring of several servo drives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1.5 Fault exclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1.6 Safety relay unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1.7 Interfaces of the PDS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5 Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1 Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.2 STO installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.3 SS1-t installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.4 Installation for operation without safety function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.5 Connection Examples, Cross-wiring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6 Commissioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.1 Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.2 Check lists. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7 Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8 Malfunctions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.1 Diagnostics via LEDs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.2 Repair. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
9Technical data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.1 Technical data, safety engineering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.2 Technical data, general. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
9.3 Technical data, electrical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
9.3.1 Digital inputs and outputs [X1A]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

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Safety
1 About this document
1.1 Target group
The document is targeted towards individuals who mount and operate the product. It is additionally
targeted towards individuals who are entrusted with the planning and application of the product in a
safety-oriented system.
1.2 Applicable documents
This document describes the use of the safety sub-function safe torque off (STO/Safe torque off) in
accordance with EN 61800-5-2.
It is possible to implement the safety sub-function safe stop 1 time controlled (SS1-t/Safe stop 1 time
controlled) with a suitable external safety relay unit and appropriate servo drive circuitry.
•Observe the safety instructions in the documentation è Operating instructions Assembly Instal-
lation Safety sub-function.
All available documents for the product è www.festo.com/sp.
1.3 Product version
This documentation refers to the following version:
–Servo drive CMMT-ST-...-S0, revision 1 and higher, see product labelling.
1.4 Product labelling
Product labelling è Manual Assembly, Installation.
1.5 Specified standards
Version
EN ISO 12100:2010-11 EN 61800-5-1:2007+A1:2017
EN ISO 13849-1:2015 EN 61800-3:2004+A1:2012
EN ISO 13849-2:2012-10 EN 61800-5-2:2017
EN ISO 14118:2018-02 EN 61800-2:2015
EN 60204-1:2018-09 EN 61508 Parts 1-7:2010
EN 61131-2:2007 EN 62061:2005+AC:2010+A1:2013+A2:2015
Tab. 1: Standards specified in the document
2Safety
2.1 Safety Instructions
This product can generate high frequency malfunctions, which may make it necessary to implement
interference suppression measures in residential areas.
It is only possible to determine whether the product is suitable for specific applications by also
assessing further components of the subsystem.
Analyse and validate the safety function of the entire system.

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Safety
5
Check the safety functions at adequate intervals for proper functioning. It is the responsibility of the
operator to choose the type and frequency of the checks within the specified time period. The manner
in which the test is conducted must make it possible to verify that the safety device is functioning
perfectly in interaction with all components. Time period for cyclical test è 9.1 Technical data, safety
engineering.
Prior to initial commissioning, wire the control inputs of the safety sub-function STO. The safety
sub-function STO-t is always available without the need for any additional parameterisation.
Keep the documentation somewhere safe throughout the entire product lifecycle.
2.2 Intended use
The safety function might fail, malfunctions might occur, and the connected actuator technology
might move unintentionally if you do not comply with the parameters required for the ambient and
connection conditions.
The CMMT-ST-...-S0 supports the following safety sub-functions in accordance with EN 61800-5-2:
–safe torque off (STO/Safe torque off)
–safe stop 1 time controlled (SS1-t/Safe stop 1 time controlled) can only be implemented with a
suitable safety relay unit and appropriate servo drive circuitry
The safety sub-function STO is intended to switch off the torque of the connected motor, thereby
preventing an unexpected restart of the motor.
The safety sub-function SS1-t is intended to perform a fast stop with subsequent torque switch-off.
Ensure that wiring is cross-circuit proof in accordance with EN ISO 13849-1.
2.2.1 Range of application
The device is intended for use in an industrial environment.
Safety sub-functions may only be used for applications for which the stated safety reference values
are sufficient è Technical data.
2.2.2 Permissible components
The load and logic power supply must meet the requirements of EN 60204-1 (protective extra-low
voltage, PELV).
2.3 Foreseeable Misuse
Foreseeable misuse of the safety sub-function STO
–Use outside the limits of the product defined in the technical data.
–Bypassing of the safety function.
–Cross-wiring of the diagnostic feedback signals of more than 10 servo drives. This applies to all
devices that are wired together, regardless of the type of equipment.
–Faults in the cross-wiring of passive diagnostic contacts and active diagnostic outputs will result
in incorrect diagnostic feedback. It is therefore important to take extra care when carrying out the
cross-wiring. Only wire devices as follows: Always wire all devices with active diagnostic output,
e.g. CMMT-AS, in parallel as a group. Connect the signal from the active diagnostic outputs with the
first CMMT-ST. Wire the passive diagnostic contacts as a group in series and connect the last pas-
sive diagnostic contact directly to the safe controller for evaluation of the diagnostic information.
–Use of the diagnostic contact STA to switch a safety function.

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Safety
The diagnostic contact STA must not be used to open a secure locking mechanism directly,
for example.
The diagnostic contact STA is not part of the safety circuit. The diagnostic contact STA is used to
improve diagnostic coverage of the related safety sub-function. The diagnostic contact STA may only
be used in combination with the related safe control signals (AND operation) plus a reliable time
monitoring function in the safety relay unit for the purpose of switching additional safety-critical
functions.
–At low level, the safety relay unit used delivers a higher current than permissible (maximum
permissible input current exceeded with low level at STO-/A/B è Tab. 19 Control inputs #STO-A and
#STO-B at [X1A]). When this occurs, the device cannot recognise when the safety sub-function is
requested.
–Use of the safety sub-function STO without external measures for drive axes influenced by external
torques.
If external torques influence the drive axis, use of the safety sub-function STO on its own is
not suitable for stopping the axis safely. Additional measures are required to prevent dangerous
movements of the drive axis, such as use of a mechanical brake.
–Operation of EC motors requiring a safety classification of SIL 3, cat. 3, Pl e without evaluation of
the diagnostic contact STA.
–Operation of the connected motor without the danger zone being restricted or enclosed by suitable
means.
The user must not be able to enter the danger zone without triggering the safety function.
–The safety sub-function STO does not provide protection against electric shock, only against dan-
gerous movements.
–The safety sub-function STO cannot prevent non-safety-related sub-functions from failing, e.g. the
braking ramp for the SS1-t function or the device's temperature monitoring function.
2.4 Training of qualified personnel
The product may be installed and commissioned only by a qualified electrical engineer who is familiar
with:
–The installation, operation and maintenance of electrical control systems
–The applicable regulations for operating safety-related systems
Work on safety-related systems may only be carried out by qualified personnel trained in safety
engineering.
2.5 CE marking
The product has the CE marking.
The product-related EU directives and standards are listed in the declaration of conformity
è www.festo.com/sp.
2.6 Safety engineering approval
The product is a safety device in accordance with the EC Machinery Directive. For details of the
safety-oriented standards and test values that the product complies with and fulfils, see è 9.1
Technical data, safety engineering. Please note that compliance with the listed standards is limited to
the CMMT-ST-...-S0.

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Product overview
7
3 Additional information
–Contact the regional Festo contact if you have technical problems è www.festo.com.
4Product overview
4.1 Safety sub-functions
4.1.1 Function and application
The servo drive CMMT-ST-...-S0 has the following safety-related performance features:
–Safe torque off (STO/Safe torque off)
–Safe stop 1 time controlled (SS1-t/Safe stop 1 time controlled) with use of a suitable external safety
relay unit and appropriate servo drive circuitry
–Diagnostic contact STA for feedback of the active safety sub-function STO
4.1.2 Safety sub-function STO
Fig. 1: Symbol for STO
The function described here implements the safety sub-function STO according to EN 61800-5-2
(corresponds to stop category 0 from EN 60204-1).
The safety sub-function STO is used when the power supply to the motor needs to be switched off
safely in the application but there are no further requirements for a targeted standstill of the drive
(such as stop category 1 from EN 60204-1 è Safety sub-function SS1-t).
Function and application of STO
The safety sub-function STO switches off the driver power supply for the power semiconductor, thus
preventing the power output stage from supplying the energy required by the motor. The power supply
to the drive is safely disconnected when the safety sub-function STO is active. The drive cannot
generate torque and so cannot perform any dangerous movements.
With suspended loads or other external forces, additional measures must be put in place to prevent
movements being performed (e.g. mechanical clamping units). In the STO state, the standstill position
is not monitored.
The machines must be stopped and locked in a safe manner. This especially applies to vertical axes
without automatic locking mechanisms, clamping units or counterbalancing.

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Product overview
Functional principle of STO
Fig. 2: Functional principle of STO
STO request
The safety sub-function STO is requested on 2 channels by simultaneously switching off the control
voltage at both control inputs #STO-A and #STO-B.
The signals of inputs #STO-A/B are low active, so they are marked with #.
The drive behaves as follows when the safety sub-function STO is requested:
–Behaviour of the drive with a running motor: the movement of the drive is not decelerated via a
braking ramp. The drive continues to move uncontrolled due to inertia or external forces until it
comes to a standstill by itself.
–Behaviour of the drive with a stopped motor: the drive is uncontrolled and can be moved by external
forces.
The safe state is achieved after the safety sub-function STO has been requested if all motor coils are
switched off and current cannot flow through them.
NOTICE
Detent movement if the output stage fails.
If the output stage of the device fails when a safety sub-function STO is active, it may result in
the drive jerking with a limited detent movement of the rotor. The maximum rotation angle/travel
corresponds to the pole pitch of the motor used.
•Take this behaviour into account when designing the system's safety function.
After the safety sub-function STO has been requested and the request completed, the functional
controller enable must be activated.
Feedback via diagnostic contact STA
The state of the safety sub-function STO can be reported to the safety relay unit via the diagnostic
contact STA.

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Product overview
9
If the safety classification of SIL 3, cat. 3, Pl e is required for operation with an EC motor, the diagnostic
contact STA must be evaluated.
The diagnostic feedback signal STA has been designed as a potential-free contact (opto relay). The
diagnostic contact STA is only closed (conductive) when STO is requested on 2 channels via the control
inputs #STO-A and #STO-B. If the contact is closed (conductive), the STO state has been achieved (safe
state).
#STO-A #STO-B STA-C1/C2
Low level Low level Diagnostic contact closed (low resistance)
Low level High level Diagnostic contact open (high resistance)
High level Low level
High level High level
Tab. 2: State of the diagnostic contact STA
If the safety sub-function STO is not requested but protective functions are triggered simultaneously
on both channels (#STO-A and #STO-B), e.g. if the voltage at #STO-A and #STO-B is too high, the
internal protective functions switch off the channels as if STO had been requested and the diagnostic
contact STA is closed (safe state feedback).
Recommendation: The safety relay unit should check the state of the diagnostic contact whenever
there is an STO request. The state of STA must change according to the logictable. The safety relay unit
can cyclically test the #STO-A and #STO-B signals for high level with low testpulses and for low level
with high testpulses, within the specified limits è 4.1.6 Safety relay unit.
The diagnostic contact STA is not evaluated in terms of safety engineering.

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Product overview
STO timing
Fig. 3: STO timing graph (example with low test pulses)
Legend for STO timing
Term/abbreviation Explanation
#STO-A/#STO-B 2-channel input for STO request
#STO-PWM1/#STO-
PWM2
Internal control, PWM driver 1 and 2
tSTO,TP Length, low test pulses1) at #STO-A/B
tSTO,In Max. delay until STO switches off (≤ permissible reaction time when a safety
sub-function is requested1))
STA Feedback, STO active
tSTA,Rise Maximum permissible delay1) for diagnostic feedback after the safety func-
tion is requested

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Product overview
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Term/abbreviation Explanation
tSTA,Fall Maximum permissible delay1) for diagnostic feedback after the safety func-
tion request has ended
n Rotational speed
1) See Technical data, safety reference data for STO
Tab. 3: Legend for STO timing
4.1.3 Safety sub-function SS1-t
Fig. 4: Symbol for SS1
The function described here implements the safety sub-function SS1-t according to EN 61800-5-2.
The safety sub-function SS1 is used when the motor needs to be braked and the power supply to the
motor then has to be safely switched off in the application but there are no further requirements for a
targeted standstill of the drive (controlled stop, stop category 1 according to EN 60204-1).
Together with a suitable safety relay unit, the following can be achieved:
–Safe stop 1 time controlled (SS1-t/Safe stop 1 time controlled); triggering of motor deceleration
and, after an application-specific time delay, triggering of the safety subfunction STO
Requirements of SS1-t
–Wire the safety sub-function STO.
–Execute emergency stop command by means of the safety relay unit (either directly by wiring
CTRL-EN accordingly or indirectly via a further functional controller).
–The time for executing an emergency stop is known.
–The safety relay unit supports programmable timers and simple logic elements.
Function and Application of SS1-t
The procedure for triggering SS1-t comprises the following steps:
1. Request for a functional emergency stop (e.g. remove CTRL-EN signal)
This causes the servo drive to trigger a braking ramp function and – if present – allows the brake
function to engage at the end of the braking ramp. On completion of the braking ramp and once
the parameterisable delay time for brake closing has elapsed, the power stage is functionally
switched off.
2. Start of a time-delay element for control of STO
3. Request for a safety sub-function STO once the delay time has elapsed
The figure below shows the necessary logic circuits for the safety relay unit:
The delay times are directly included in the reaction time of the system.

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Product overview
SS1-t Feedback
The STA signal can be used as feedback for the safety sub-function SS1-t.
SS1-t Timing
Fig. 5: SS1-t timing graph
Legend for SS1-t timing
Term/abbreviation Explanation
Timer Delay element in safety relay unit
CTRL-EN Enable signal
tDelay Delay time until STO request
#STO-A/B 2-channel input for STO request
STA Feedback, STO active
t1Braking ramp completed (controlled functionally), rotational speed = 0
t2Brake closed (if present) and output stage switched off (functionally)
t3t3 > t2
n Rotational speed
Tab. 4: Legend for SS1-t timing

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Product overview
13
• If there are suspended loads and a motor with holding brake is used, they usually drop if STO is
requested immediately before the braking ramp has elapsed, because the engagement time of
the holding brake plays a significant role.
• The time t3 must always be set to a value longer than the total of the braking ramp time t1 and the
brake engagement time (t2 – t1). This prevents the following:
• Suspended loads potentially dropping
•Increased wear on the holding brake
• When selecting the delay time tDelay, make sure it is long enough to take account of the maximum
braking ramp time and brake engagement time.
4.1.4 Cross-wiring of several servo drives
Whether cross-wiring of the diagnostic contact is permissible depends on the safety classification
required.
The diagnostic contact must be evaluated separately for EC motors with the classification SIL 3, cat. 3,
PL e. It is not permissible to cross-wire the diagnostic contact. In all other cases, the following rules
apply when cross-wiring several servo drives:
–Wire inputs #STO-A and #STO-B in parallel in each case.
–Wire diagnostic contacts STA-C1/C2 in series in each case.
–Wire the diagnostic contacts of a maximum of 10 servo drives in series. The maximum cable length
applies to the entire line, from the safety relay unit to the final device.
Example of cross-wiring è 5.5 Connection Examples, Cross-wiring.
4.1.5 Fault exclusion
Put suitable measures in place to prevent faulty wiring:
–Exclude wiring faults in accordance with EN 61800-5-2
–Configure the safety relay unit to monitor the outputs of the safety relay unit and wiring up to the
servo drive
4.1.6 Safety relay unit
Use suitable safety relay units with the following characteristics:
–2-channel outputs with
–Detection of shorts across contacts
–Required output current (also for STO)
–Evaluation of the diagnostic contact of the servo drive
Safety relay units with test pulses can be used with the following restrictions:
–High test pulses up to a maximum length of 1 ms
–Low test pulses up to a maximum length of 1 ms
–Test pulses are not simultaneous/overlapping on #STO-A/B
The safety relay units Pilz PNOZmulti, Pilz PNOZmulti Mini or SIEMENS SIMATIC ET 200SP with
PP-switching output modules, SIEMENS ET 200S, for example, would be suitable.
The input module CPX-F8DE and output module CPX-FVDA-P2 from Festo would be suitable too.
Comment: The safe output module CPX-FVDA-P2 can only switch potential-free loads. It can only be
used, therefore, in combination with an interposed relay, since #STO-A and #STO-B are referred to

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Installation
GND. Detection of shorts across contacts is then only possible as far as the relay. Detection of shorts
across contacts is not possible on the CMMT-ST itself, so cross-circuit-proof wiring is required in this
case.
4.1.7 Interfaces of the PDS
The interfaces of the PDS(SR) (Power Drive System, safety related in accordance with EN 61800-5-2) to
the outside world are:
–Power supply
–Inputs and diagnostic feedback signals
–Movement of the shaft
5 Installation
5.1 Safety
WARNING
Risk of injury due to electric shock.
• For the electrical power supply with extra-low voltages, use only PELV circuits that guarantee a
reinforced isolation from the mains network.
• Observe IEC 60204-1/EN 60204-1.
Comprehensive information concerning the electrical installation of the device è Manual Assembly,
Installation.
Information for operation with safety functions
NOTICE
Check the safety functions to conclude the installation process and after every modification to the
installation.
During installation of safety-related inputs and outputs, also observe the following:
–Meet all specified requirements, e.g.:
–Surrounding area (EMC)
–Logic and load voltage supply
–Mating plug
–Connecting cables
–Cross-wiring
Additional information è Manual Assembly, Installation.
–The maximum permissible cable length between the safety relay unit and the plug of the I/O
interface is 25 m.
–During installation, make sure you meet the requirements of EN 60204-1 relating to the use of PELV
fixed power supplies. In the event of a fault, the voltage must not exceed 60 V DC. The safety relay
unit must switch off its outputs in the event of a fault.

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–A PELV fixed power supply must be used for the safety relay unit and the logic power supply of the
CMMT-ST. The GND (0 V) of the two fixed power supplies must also be connected to each another.
The device power supply and the power supply of the STO inputs must refer to the same GND
potential.
–The wiring between the safety relay unit and the I/O interface of the servo drive must be installed
to ensure that the risk of a short circuit between the conductors or to 24 V, as well as a cross circuit
can be eliminated è EN 61800-5-2, Annex D.3.1. Otherwise, the safety relay unit must feature
detection of shorts across contacts and, in the event of a fault, must switch off the control signals
on 2 channels.
–Only use suitable mating plugs and connecting cables è Manual Assembly, Installation. Use wire
end sleeves for multicore wires.
–Avoid conductive contamination between neighbouring plug pins.
–Make sure that no bridges or similar can be inserted parallel to the safety wiring. For example, use
the maximum wire cross section or appropriate plastic wire end sleeves.
–To cross-wire safety-related inputs, use twin wire end sleeves. When cross-wiring STA diagnostic
contacts, a maximum of 10 devices may be cross-wired è Manual Assembly, Installation.
–The safety relay unit and its inputs and outputs must meet the necessary safety classification of the
safety function required for the specific case.
–Connect each of the control inputs to the safety relay unit on 2 channels.
–If the STA feedback signal of the STO safety sub-function has to be evaluated: connect diagnostic
contact directly to the safety relay unit. The diagnostic contacts must not be connected in parallel,
since a device like this with an active safety sub-function would report a safe state for all devices.
–Whether the diagnostic contact needs to be evaluated depends on the type of motor that is
connected and the desired safety classification.
–If diagnostic contacts are cross-wired for a device compound: wire diagnostic contacts in series.
Basic circuitry concept
–Safe sensors – e.g. emergency stop switches, light curtains – are routed to the safety relay unit (or
the safety PLC).
–The safety relay unit requests the safety sub-function on the servo drive via 2 channels and
evaluates the feedback signal STA.
5.2 STO installation
Inputs and outputs for the safety sub-function STO
The 2-channel request for the safety sub-function is made via the digital inputs #STO-A and #STO-B.
The digital input #STO-A must not be connected to the digital input #STO-B. Make sure that no bridges
or the like can be used parallel to the safety sub-function.
The diagnostic contact STA indicates whether the safe state has been reached for the safety sub-func-
tion STO.

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[X1A] Pin Type Identifier Function
X1A.
2
Digital input #STO-A Safe torque off, channel A
X1A.
3
#STO-B Safe torque off, channel B
X1A.
4
Contact STA-C1 Safe torque off acknowledge, diag-
nostic contact
X1A.
5
STA-C2
Tab. 5: Inputs and outputs for the safety sub-function STO
The motor controller cannot detect a cross circuit in the input circuit by itself.
1. Find out if detection of shorts across contacts is needed for the input circuit and diagnostic
contact wiring in the application.
2. If required, use a safety relay unit with detection of shorts across contacts.
STO connection example
In this example, the safety sub-function STO (safe torque off) is triggered by an input device that
makes the safety request (e.g. light curtain).

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12 3
4
Fig. 6: STO sample circuit
1Input device for safety request (e.g. light
curtain)
2Safety relay unit
3Servo drive
4Drive axis
Information on the sample circuit
The safety request is passed on to the servo drive on 2 channels via the inputs #STO-A and #STO-B at
the connection [X1A]. This safety request results in the 2-channel switch-off of the driver supply to the
servo drive’s power output stage.
The safety relay unit can use the diagnostic contact STA to monitor whether the safe state has been
reached for the safety sub-function STO.
The CTRL-EN wiring shown is not required for the safety sub-function STO.

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Information on using EC and stepper motors
When using stepper motors with a safety classification of SIL 3, cat. 3, Pl e and EC motors with a safety
classification of SIL 2, cat. 3, Pl d, it is not mandatory to have a safety relay unit or to evaluate the
feedback signal STA. The following components can be connected to the control inputs #STO-A and
#STO-B to request the safety sub-function STO:
–Safe semiconductor outputs (electronic safety relay units, active safety sensors, e.g. light curtains
with OSSD signals; OSSD = "Output Signal Switching Device")
–Switch contacts (safety relay units with relay outputs, passive safety sensors, e.g. forced position
switches)
When using EC motors that require a safety classification of SIL 3, cat. 3, Pl e, it is necessary to have
a safety relay unit and to evaluate the feedback signal STA via the diagnostic contact STA. It is not
permitted to connect safe sensors directly.
5.3 SS1-t installation
Inputs and outputs for the safety sub-function SS1-t
The safety sub-function SS1-t is wired like the safety sub-function STO but is supplemented by
an emergency stop request (either directly by wiring CTRL-EN or indirectly via another functional
controller) so that the braking ramp can be activated by the safety relay unit.
5.4 Installation for operation without safety function
For operation without the safety subfunction, wire inputs X1A.2 to X1A.5 as follows:
[X1A] Pin Type Identifier Function
X1A.
2
Digital
input
#STO-A Supplies each one with 24 V
X1A.
3
#STO-B
X1A.
4
Contact STA-C1 Do not connect
X1A.
5
STA-C2
Tab. 6: Circuitry of inputs and outputs without safety sub-function
5.5 Connection Examples, Cross-wiring
The following rules apply when cross-wiring several servo drives:
–Wire inputs #STO-A and #STO-B in parallel in each case.
–Wire diagnostic contacts STA-C1/C2 in series in each case.
–Wire the diagnostic contacts of a maximum of 10 servo drives in series.
The maximum cable length applies to the entire line, from the safety relay unit to the final device.
Connection Example for Cross-wiring Several Devices without Checking the Diagnostic Contact
The first diagnostic contact of the CMMT-ST must be supplied with 24 V. The diagnostic contacts of the
sequential devices must then be wired in series. Connect the last diagnostic contact for evaluating the
diagnostic information to the safe controller.

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With this type of wiring, the safe controller cannot perform diagnostics on whether a diagnostic
contact of a CMMT-ST is permanently conductive with a short circuit on the output. For this reason,
this type of wiring is not permitted for operation with EC motors and the required safety classification
in accordance with SIL 3, cat. 3, Ple.
Fig. 7: Connection example for cross-wiring several devices without checking individual diagnostic
contacts
Connection Example for Cross-Wiring Several Devices with Checking the Diagnostic Contact
If it is required for the overall assessment of the system that the safe controller can perform diagnos-
tics with diagnostic contacts, the diagnostic contacts may not be connected in series. In these cases,
the diagnostic contacts must be individually connected on separate inputs of the safe controller.
The inputs #STO-A and #STO-B can continue to be wired in parallel.

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Fig. 8: Connection example for cross-wiring several devices with checking of individual diagnostic
contacts
Connection example for mixed cross-wiring of devices with diagnostic contact (CMMT-ST) and
diagnostic output (e. g. CMMT-AS)
If errors are made when wiring the diagnostic contacts, they will cause incorrect diagnostic feedback
signals. With mixed wiring, special care is therefore needed. Only wire devices as described below.
Devices with diagnostic output must always be wired in parallel, e. g. all CMMT-AS. The signal must
then be connected to the diagnostic contact of the first CMMT-ST. The diagnostic contacts must then
be wired in series. The last CMMT-ST must then be connected to the safe controller for evaluation of
the diagnostic information.
This type of wiring is not permitted for operation with EC motors and the required safety classification
to SIL 3, cat. 3, Ple (è Fig. 8). Here, the diagnostic contacts of the CMMT-ST must be individually
evaluated.
The maximum number of 10 devices applies in this case for all devices wired together, regardless of
the type.