Question:
When is the elapsed time meter (C0178) and the elapsed hour meter (C0179) stored in EEPROM?
Answer:
The elapsed time (C0178) and elapsed hour meter (C0179) is stored in EEPROM only in case of mains switch off (intermediate circuit voltage ~ 0 V), as due to permanent writing on EEPROM it can be destroyed. (The EEPROM can execute approx. 100.000 write cycles). A defect in the device (e. g. destruction of a switch mode power supply) can cause incorrect storage of the elapsed time and elapsed hour meter, This would lead to a stored operating time in the EEPROM shorter than the actual time.
Example:
A new device (C0178 = 0 hours, C0179 = 0 hours) is commissioned in a machine. After 5 hours it is switched off for the first time. Within these 5 hours the drive controller has been enabled for 3 hours (terminal 28 = HIGH). Therefore, in EEPROM 3 hours are stored for the elapsed time meter (C0178) and 5 hours for the elapsed hour meter (C0179). When the drive controller is restarted and after another 1000 hours the switch mode power supply fuse fails (defect), the elapsed time and elapsed hour meter is not stored correctly. This means, the EEPROM still stores 3 and 5 hours for the elapsed time and elapsed hour meter, although the device was operated more than 1000 hours.
