Most of these devices do not publish their power requirements anymore, something of a modern phenomena in the it just works age you don't need to know the details. I found an older device that required a max of 500ma in high power mode, 45ma standby/idle and 180ma connected. This device listed Vista as the newest OS supported so that would have been around 2007 ish.
Someone that measured some USB 3G/4G modems published results showing a max of 308ma, 130-170 avg. and 38ma min. With the units tested.
The SP3 conforms to the 900ma power spec for USB so these should work fine with typical max draw under 500ma or less. If it exceeds the 900ma it's going to power cycle. In the unlikely event it draws that much power there's either something wrong with it or it's just a power hog and you should try a different model.