IEC 61800-5-2 pdf download – Adjustable speed electrical power drive systems – Part 5-2: Safety requirements – Functional

IEC 61800-5-2 pdf download – Adjustable speed electrical power drive systems – Part 5-2: Safety requirements – Functional
4 Designated safety functions
4.1 General This clause describes functions of a PDS(SR) that may be designated as safety-related by the PDS(SR) supplier. The designated safety functions in this clause are not considered to form an exhaustive list. In some cases, further safety-related systems external to the PDS(SR) (for example a mechanical brake) may be necessary to maintain the safe condition when electrical power is removed. The technical measures required to implement these functions depend on the SIL capability and the required probability of dangerous hardware failure, as indicated in the safety requirements specification.
The technical measures are described in Clause 6. Each safety function may require safe input and/or output signalling in order to accomplish necessary communication with (or activation of) other functions, subsystems or systems (which may or may not be safety-related). The integrity of the interfaces shall be included in the determination of the SIL of the associated safety function. Some of the safety functions perform monitoring tasks only, some perform a safety relevant control or other actions. Therefore, a distinction must be made between: − the reaction on violation of limits (only relevant for monitoring functions):
the reaction function when a violation of limits is detected during the correct operation of the safety function; and
− the fault reaction function: the reaction function when diagnostics detect a fault within the safety function. Both reaction functions shall take into account the possible safe states for the application. On selecting the appropriate reaction function, it has to be considered that parts of the PDS(SR) may not be functioning.
Timing requirements for the actions required following detection of a fault are specified in the safety requirements specification (see 5.4.2).
The names of the safety functions include the words “safe” or “safely” to indicate that these functions may be used in a safety-related application on the grounds of a judgement (i.e. risk analysis) of that specific application, resulting in safety-relevant functions and their integrity tobe performed by the PDS(SRy.
4.2Safety functions
4.2.1 Limit values
Where a safety function relies on limit value(s) for any parameter(s)，the maximumtolerance(s ) for the limit value(s) shall be defined.
NOTESpeclfication of any limit value should take into account possible exceeding of the limit value in case ofviolation of the limit,For example,5pecification of the position limit value(s) in 4.2.3.8 should take into account themaximum allowable owertravell distance(S).
A particular safety function may have one or more specified limit values,which can beselected during operation.
4.2.2Stopping functions4.2.2.1General
Avariety of stopping methods is available for every type of PDS.
The control requirements for initiating the stopping sequence and maintaining a hold modeupon reaching standstill are application-specific. “Separate manual operations andconnections to control circuits may be necessary to achieve the desired performance of thestop functions.
Any particular requirements for stopping performance should be specified by the installationdesigner.The following examples of stop functions are often used in practice.
4.2.2.2safe torque off (STo)
Power, that can cause rotation (or motion in the case of a linear motor), is not applied to themotor.The PDS(SR) will not provide energy to the motor which can generate torque (or forcein the case of a linear motor).”
NOTE1_ This safety function corresponds to an uncontrolled stop in accordance with stop category 0 ofIEC 60204-1.
NOTE 2 This safety function may be used where power removal is required to prevent an unexpected start-up.
NOTE 3 ln circumstances where external influences (for example，falling of suspended loads)are present,additional measures (for example,mechanical brakes) may be necessary to prevent any hazard.
NOTE4 Electronic means and contactors are not adequate for protection against electric shock，and additionalmeasures for isalation may be necessary.
4.2.2.3Safe stop 1 (sS1)The PDS(SR) either
a) initiates and controls the motor deceleration rate within set limits to stop the motor andinitiates the ST0 function (see 4.2.2.2) when the motor speed is below a specified limit; orb) initiates and monitors the motor deceleration rate within set limits to stop the motor and
initiates the STO function when the motor speed is below a specified limit; or
c) initiates the motor deceleration and initiates the STo function after an application specific
time delay.
NOTE This safety function corresponds to a controlled stop in accordance with stop category 1 of lEC 60204-1.