Dave Tweed wrote:
>3-phase induction motor controller that could be run from a single phase line. I don't believe I've ever seen such a product...

There is plenty of them, and several manufacturers to say the least...
I recently have looked around for VFD:s...

Google for VFD drives
VFD = Variable Frequency Drives

Low power units are usually one phase in, high power usually three phase, ranges overlap.


I found simple v/f VFD are so cheap theese days it is no win in building them oneself, even for series production.  For example Hitachi L100 is a nice simple one phase in v/f VFD, available in 200, 400 and 750W.  SJ100 has added vector control (a kind of sensorless rpm control) and brake.

The expensive VFD:s have nice algoritms for exact rpm, torque control, and power savings.  Some also have positioning algorithms built-in, and at least one network type (RS485, Devicenet...)

There are even some that do clean sine output so they can be used to drive motors thruogh hundreds meters long standard cables with no problem - while doing decent sensorless rpm feedback and control.  True sine also does not have the power loss problems in the motor as PWM VFD:s (making energy waste and motor power degradation), and des not have the problem with bearing wear due to induced currents.  Cost more initailly, but saves energy, motor wear, service cost, thus total cost.  Targetted mainly at Pumpand fan driving for primarily energy optimization, and noise and wear reduction.  NFO Drives are specialised in this, and Siemens also have some sine converters.

/Morgan

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