Electronic – Buffering AC supply voltage and detect power loss

acbufferpower supplyups

I'm designing a system integrating:

  1. an industrial PC with 230V AC input (~300W)
  2. various peripherals requiring 24V DC (150W max)

In case of external AC power loss, the DC components (2) need to be supplied with backup power for up to five minutes. This is not a problem and suitable PSU are available.

However, for a reason I cannot control, the industrial PC requires an advance signal (about 1 second in advance, possibly less) indicating that its supply power is about to be lost.

So I'm looking for suitable 230V AC buffer with power loss notification. Compliance with IEC 60601-1 (3rd) would be a big plus.

I don't know exactly what I'm looking for. I would like to avoid a full-blown UPS, even though a battery is needed for the 24V PSU. Could anyone direct me to the right kind of component?

Best Answer

Placing UPSes here and there is a primary instinct for almost every automation engineer. But it is not a good solution, especially on big systems (which the discussed one is not). The two main disadvantages of powering from UPS is:

  1. The UPS has batteries inside. All types of batteries degrades with the time and need replacement. But any support work on the industrial machinery is not good by definition.

  2. Using UPS on some part of the machine (usually computers) means that on power loss, the system goes to inconsistent state, that is rarely processed properly by the software. As a result there are often restart problems after power restoration. Such a machines need very careful design and extended testing.

So, on the topic. I would suggest following variants:

  1. Think again - is it really, really so important to keep the PC working after the power fault? Isn't it possible by some software methods to make that shut-down to not lead to information loss?

  2. If the answer of 1. is "No", then use industrial PC powered by 24VDC and use capacitive backup device that will keep the voltage for at least several seconds or minute and will switch it for the whole machine. In addition, it will not need support and battery replacements.

Note: We have the cited Wöhrle devices in several of our plant machines.

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