If there is a requirement for a UPS system that is to be used in the vicinity of a patient then that UPS should be compliant with the requirements of the standard EN60601-1, or equivalents IEC60601-1, UL2601-1. These standards define the requirements for electrical safety and the main difference between this and the traditional UPS standards is the very strict limits on earth leakage.
Standard UPS limits under 3KVA can have earth leakage of no more than 3mA, and with EMC filters employed you will normally find pluggable UPS systems to have earth leakage in the 1 to 2mA region, whereas the medical standard calls for earth leakage to be no more than 300?A, a factor of 10 more stringent. (EN60601 goes into a lot more detail, but the rest of it is pretty much the requirement for medical devices, and a UPS is not a medical device).
As a result there is niche for UPS systems that fall into this category for patient vicinity applications. So when is a UPS in the vicinity of a patient? Well, this used to be well defined by drawing an arbitary box around the patient and figuring out where the UPS can go, however, now the method employs a risk assessment method, so basically you work out the liklihood of the patient touching the UPS and potentially interfering with any equipment he has attached to him at the time. Typical applications for this include patient monitors, ultrasound systems, PC’s etc, however the manufacturers of these UPS systems put a big disclaimer that under no circumstances should they be used on life support applications. I guess this is just because of the risk of being sued if something goes wrong with the system.
Powervar and Oneac manufacture a range of systems to fulfil this requirement. Powervar has a wider range and are true sinewave VI (Line Interactive) products. Oneac’s (part of Chloride) have extended run capabilities and are slightly cheaper as they have a pseudo-sine inverter (OK – a square wave). [Aside: Come on Oneac - why not make this product sine wave when you're known for great power quality products???].
UPSMart stock a range of Medical Grade UPS Systems.
Just another point to add to this, an interesting side effect of using medical grade ups systems is that the earth leakage of all connected equipment is in fact reduced to <300uA. This is because of the isolation transformer used to achieve the low leakage in the first place. I’ve seen this technique used so that hospitals can save money on expensive specialist PC hardware and instead opt for medical grade UPS (or power conditioner!) and standard PC & monitor.
Comment by toneus — October 22, 2008 @ 2:24 am