Yes, cheaper UPS or Inverters do not have a good clean SINE wave output (AC Signal), it can make your motors hum and possibly burn them out.
Mine does that, mine is a Modified SINE wave output, but it doesn't run long. Most of the UPS are designed for Computers, and they don't care about the output, since it converts them down to 5 and 12V DC anyway.
If you invest in a good one, it should have a FULL Sine Wave Output, but they can start around $250-UP, long term power outages, you are better off with a small (2500W or higher) generator. Like he said, you can run other stuff too!