Adjustable speed electrical power drive systems - Part 5-3: Safety requirements - Functional, electrical and environmental requirements for encoders

This part of IEC 61800, which is a product standard, specifies requirements and makes recommendations for the design and development, integration and validation of safety-related encoder (Encoder(SR)) in terms of their functional safety considerations, electrical safety and environmental conditions. It applies to Encoder(SR), being sensors as part of a PDS(SR). NOTE 1 The term "integration" refers to the Encoder(SR) itself, not to its incorporation into the safety-related application. This document can also be referred to and used for Encoder(SR) in any other safety-related application, for example safety-related position monitoring. NOTE 2 This document specifies only complementary functional safety, electrical safety and environmental condition requirements that are not clearly provided by other parts of the IEC 61800 series. This document is applicable where functional safety of an encoder is claimed and the Encoder(SR) is operating mainly in the high demand or continuous mode. NOTE 3 While low demand mode operation is possible for an Encoder(SR), this document concentrates on high demand and continuous mode. Safety sub-functions implemented for high demand or continuous mode can also be used in low demand mode. Requirements for low demand mode are given in IEC 61508 (all parts) [2]. Some guidance for the estimation of average probability of dangerous failure on demand (PFDavg) value is provided in IEC 61800-5-2:2016, Annex F. The requirements of IEC 61800-5-2:2016 for PDS(SR) apply to Encoder(SR) as applicable. This document includes additional or different requirements for Encoder(SR). It sets out safetyrelated considerations of Encoder(SR) in terms of the framework of IEC 61508 (all parts), and introduces requirements for Encoder(SR) as subsystems of a safety-related system. It is intended to facilitate the realisation of the electrical/electronic/programmable electronic (E/E/PE) and mechanical parts of an Encoder(SR) in relation to the safety performance of safety sub-function(s) of an Encoder(SR).