I've been trying to find the max voltage rating of the 24VDC digital inputs on the Micromaster 420/440 drives from Siemens. I have found the min/max for the On/Off levels in the manual but not the max allowed connected voltage.
I found a drive in service (for 4+ years) that had the 0VDC of the control voltage connected to the +24VDC of the drive's isolated power supply. Then the +24VDC of the control voltage was used for controlling the Digital Inputs. This put almost 50VDC on the digital inputs and it ran like this for years before the drive eventually failed. I believe the failure was due to this bad wiring, but am curious what the ratings were to allow it to run this way for over four years.
I found a drive in service (for 4+ years) that had the 0VDC of the control voltage connected to the +24VDC of the drive's isolated power supply. Then the +24VDC of the control voltage was used for controlling the Digital Inputs. This put almost 50VDC on the digital inputs and it ran like this for years before the drive eventually failed. I believe the failure was due to this bad wiring, but am curious what the ratings were to allow it to run this way for over four years.