DLMUK
Member
Hi,
I have to supply a redundant power supply (not a battery powered UPS) for a job which will kick in when a cable is broken/damaged from the OUTPUT of the primary power supply.
What I have is 24VDC output from PSU#1, this drives 45 instrumentation amplifiers. The power is passed through 7 junction boxes by the time it reaches the last amplifier. If the power cable is cut between JB3 and JB4 for example, it would cut the power to about 20 of the amplifiers, meaning that about 0.88A of current draw from the amplifier would be removed. In this instance there is a separate 24VDC from PSU#2 going down a different cable to power the same amplifiers.
What I would like to do is...
Write a PLC program to say that when the current drops below a specified level, activate a relay which switches from PSU#1 to PSU#2. This would be done when the PLC senses the current draw on PSU#1 drops too much, the logic activates a relay on the PLC which drives a high load relay to cut power from PSU#1 and run off PSU#2. There is a UPS attached to the PLC to prevent it cutting out during total power failure/switchover.
This is not something I have ever done before so there may be a better way of doing what I am suggesting?
Does anybody know of a current monitoring device I could interface with a PLC? My total current draw from the PSU is ~7A.
Thanks,
I have to supply a redundant power supply (not a battery powered UPS) for a job which will kick in when a cable is broken/damaged from the OUTPUT of the primary power supply.
What I have is 24VDC output from PSU#1, this drives 45 instrumentation amplifiers. The power is passed through 7 junction boxes by the time it reaches the last amplifier. If the power cable is cut between JB3 and JB4 for example, it would cut the power to about 20 of the amplifiers, meaning that about 0.88A of current draw from the amplifier would be removed. In this instance there is a separate 24VDC from PSU#2 going down a different cable to power the same amplifiers.
What I would like to do is...
Write a PLC program to say that when the current drops below a specified level, activate a relay which switches from PSU#1 to PSU#2. This would be done when the PLC senses the current draw on PSU#1 drops too much, the logic activates a relay on the PLC which drives a high load relay to cut power from PSU#1 and run off PSU#2. There is a UPS attached to the PLC to prevent it cutting out during total power failure/switchover.
This is not something I have ever done before so there may be a better way of doing what I am suggesting?
Does anybody know of a current monitoring device I could interface with a PLC? My total current draw from the PSU is ~7A.
Thanks,