[ICanHas]

Are you trying to discredit such a credible source? They're comparing whatever off the shelf motor drives they reviewed in 2005.

Adjustable speed motor drives are generally VVVF that raises and lowers voltage proportionately. Another viable option is a second piggy back synchronous motor driving through a one-way clutch and low tension toothed belt.

So, we're talking about providing a considerable magnetizing current and the loss associated with providing this reactive power and additional deductions must be made for motor efficiency losses if driven at a less then ideal waveform.

You're comparing it with a fixed voltage, fixed frequency China sourced stuff providing power to resistors. If the VSD is to standby, the standby power at off is counted as usage.

So, you're saying a surplus VFD driving a 1-hp 3450 RPM 60Hz motor at 1725 RPM at 1/8 hp will surpass the line-to-shaft efficiency compared to the best available 1725/3450 dual wound motor 1hp motor on both speeds while staying within 10-15% current THD on line side, and provide the same level of fault tolerance? (accidental short, motor lock up due to a sock getting sucked in, etc)

It's a freaking pool pump. You don't need a full range of ramp up, down, and speed control.