Fault classification in elevator systems

An elevator system (2, 102) comprising:

• a drive system (10) comprising one or more drive components (11, 13) and drive hardware (15) for controlling the supply of power to the one or more drive components (11, 13);
• a safety chain (16) arranged to break and thus interrupt the supply of power to the one or more drive components (11, 13), unless all of one or more safety condition(s) is satisfied;
• and
• a control device (12) arranged:
• to receive drive information from the drive hardware (15) indicative of a drive system fault;
• to receive safety chain information from the safety chain (16) indicative of a safety chain break;
• and
• to detect and classify a fault in the elevator system (2, 102) using the drive information and the safety chain information,
• wherein the safety chain is arranged to break and thus interrupt a supply of power to the one or more drive components (11, 13) on reception of a safety chain break command from the control device (12);
• wherein the control device (12) is arranged:
• to issue a safety chain break command to the safety chain (16) on reception of drive information from the drive hardware (15) indicative of a drive system fault;
• to measure a time delay between issuing the safety chain break command and receiving safety chain information from the safety chain (16) indicative of a safety chain break;
• to determine if the time delay is less than a minimum expected propagation time;
• and
• if the time delay is less than the minimum expected propagation delay, to classify the fault as a safety chain break.