Powerheads/canisters on UPS power?

[richms]

Before I go and try it and possibly smoke my pumps, how well do they cope with the squarewave power out of UPS's and inverters? I know that things with a capacitive powersupply (bug zapper) tend to blow up because of the very high amount of harmonics, I was thinking that a simple induction motor would be OK since the inductiveness of the windings would not draw excessive current like the capacitive powersupplies. But isnt there a starting capacitor and winding in these cheap little singlephase motors? Will that be ok.

ideally looking for sucess/failure stories, and if sucess how much power is lost when running on battery.

[Warren]

Shadded pole induction motors similar to those used in aquarium pumps do not usually have a cap. Some larger pumps can though (>100W).

An induction motor still has a whole pile of extra harmonics in it too. The current waveform often changes drastically and the heating is higher. Instead of bing sinusoidal with a phase-lag, the waveform ends up looking very pointy (still with a phase-lag). The RMS is still almost the same but higher harmonics cause extra heating in the iron of the stator (due to delta f cubed). The extra heating isn't a lot and the pump should work ok.

I've never tried running a pump on a quasi-squarewave type UPS. My pumps run on a dual-conversion sinewave output one.

Keep in mind, it will only be running on quasi-squarewaves when the mains is absent. This usually isn't long. For the short amount of time the pump will ever see non-sinewave voltage it should be ok. Most UPS's with long holdup times are sinewave output. Most smaller units won't run a single small pump for more then 1-2 hours anyway.

Sorry I can't be more help on this.

[Caryl]

We found the Eheim worked fine on a modified squarewave UPS but the Fluval wouldn't run at all.