Attaching SmartUPS to inverter system putting out simulated sinewave

[gwhitcroft_apc]

Hi folks - it might seem strange but I want to connect my SmartUPS 1500 and 1500i to inverter systems. The reason being that here in South Africa our power utility can't keep the lights on, so to speak, so we get periods of "load-shedding" where power is cut to an area for a few hours at a time (sometimes a few times a day!). My poor old SmartUPS can't cope with this and die after about 20 minutes of use. I therefore decided to acquire a couple of 2400VA inverter systems with big (105Ah) Deep Cycle batteries that will keep power going for 4-6 hours or so at current use rates. These put out a simulated sinewave and there is a short (20-25ms) switchover time, so I thought it would be good to keep the UPS between inverter and electronics to further smooth the current and to buffer the switch time.

However, when I do this and cut the input power to the inverter (simulating a "load-shedding" incident) I get a loud clicking sound from my 1500i, and it then gives up and runs off the UPS battery, so not recognising the power coming in. Interestingly, I can run the devices happily off the inverter output power, but would prefer to smooth that transition period as I see a short gap in comms, etc., and am also worried about things like my NAS drives, expensive TV, and so on.

Should the SmartUPS units be able to accept a simulated sinewave (it's not a stepped one, so somewhere between Stepped and Pure), and/or is there a modification I can make to the SmartUPS to accept this? Given that they're designed to handle fairly variable input scenarios, I would think/hope they could handle a stepped sinewave running between 236 and 242volts.

[BillP · Accepted solution]

Hi Guy,

Unfortunately, no. Smart-UPS will not not accept anything besides a "pure" sinewave. 

Liam