Pulling the power plug => Device damaged

Question

At work we use a certain type of video conferencing device and recently one broke down because someone pulled the power plug -- without turning off the device first. (In fact something similar happened half a year ago, after this happened a few times.)

My explanation for this is that 230 V AC abruptly become 0 V, thus high currents might be created. So it could have happened that the fuse went off. The video conferencing devices are basically modded PCs, thus having a PC power supply.

So question: is this poor design? I expect consumer devices to be more fault-tolerant. (Isn't there a norm for that?) Could it been prevented by using a surge protector:

Wall Plug <----> Surge protector <----> Device

So in this case pulling the wall plug should have left the device intact probably, right?

Edit: The brand is Vidyo.

Answer 1

230 V would become 0 V quickly, but that does not mean high currents. It can, however, mean that the currents right before power was interrupted are maintained for a short while, possibly causing bad voltages as a result.

Yes, this is bad design. There is no excuse for the device getting damaged because power was interrupted. Talk to the manufacturer. If you vaguely hint that you plan to let everyone on the internet know about your experiences with that model, they might be willing to replace it, or give you a discount on the next model up in which this problem has meanwhile been fixed. Chances are good they know about it.

Answer 2

Failure of equipment while unplugging is a known problem with poorly designed power units.

One of the reasons is multiple changes in the supply connection while pulling out the plug. Sometimes one can smell the ozone due to sparking while pulling a plug. Also, socket contacts will sometimes show blackening due to repeated unplugging with the power switch on.

Further, for devices with an inductive element facing the power line, such as a transformer, each of these power cycles over the brief period the plug contacts are being dragged out, causes backlash voltages which can be much higher than the line voltage. This can actually trip a fuse or ELCB upstream on the supply line - more so when the neutral pin of the plug is momentarily disconnected while the "hot" or live pin is still connected, as is the earth pin.

As has been stated by Olin Lathrop, a failure like this needs to be communicated back to the manufacturer in the strongest possible terms, and should result in a warranty replacement of the product.