Questions regarding the instrument power supply system
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When powering the instruments, in a cabinet with dual power supplies, can the two power sources come from the same bus? For the entire system’s power supply method as shown in the attachment: there are 2 electrical power sources—a dual-power switching box; from this switching box, one route of power is sent to the UPS and then to power source 1 inside the cabinet, while another route passes through a voltage stabilizer before reaching power source 2 inside the cabinet. Is this compliance or power supply reliable? Can different AC power sources supply power in parallel after passing through a DC switching power supply?
Our DCS isn’t like that, but there is a Siemens PLC that uses this method: after a power outage in the mains supply, the cabinet switch automatically switches to the UPS
Its normal power supply should come from the route via the UPS, and it switches to mains power in case of a UPS failure. How is the power supply for your PLC? Is it stable and reliable?
This post was last edited by rujimmy on 2020-1-13 at 17:23. In this situation, after a UPS failure, it is possible to only manually cut power and switch to the mains supply.
Two DC power supply modules are connected in parallel for power supply; as a precaution, a diode can be connected in series with each positive terminal
Is this a proposal from an environmental company that specializes in water treatment? It’s pretty crappy. 1) Although there is dual-power switching on the low-voltage cabinet side, it is not disturbance-free; there may be a few seconds of delay ； 2) It’s not easy to find a 6KVA UPS that operates on 380V AC; it has three inputs and one output, and no one designs UPS units in this way ； 3) If it is the buyer who provides the supply, I suggest you check whether it is a power-frequency UPS, so as to avoid people using high-frequency units to deceive you ； 4) UPS units of this small size generally do not come with a bypass feature; the bypass switching shown in the drawings cannot enable a seamless transition ；
This crappy wiring method is completely unprofessional
I think it would be better to combine the UPSes for the DCS and SIS into one unit, with a bypass capacity of over 10 kVA, and also dual power supplies. But I’m not sure if SIS allows such a design now; it used to be possible.
Point out where it’s not right, please :dizzy: