Does anyone have experience with using wild 3 phase to run a three phase motor direct connection

[okwindpower]

I have been working on a design for a while now that uses an axial flux PMA wound for 480 volts A.C. with the intent of coupling it directly to a small 3 phase motor.  I know that the inductive load is going to make the PMA behave differently in regards to start up, but this can be dealt with by using the proper turbine (blade) design.  Before I go beating my head against the wall, I was just wondering if anyone of you out there have any experience with such a project, and if so, what some of the problems and solutions were that you encountered.  All ideas and help is appreciated.

Mike

[Flux]

I think you are going to have to invent the wheel not reinvent it.

I assume you intend the motor to be an induction motor. I don't know how well this will work unless you have a load such as a centrifugal pump whose load characteristics may lend themselves to this type of working.

The torque of an induction motor will be very low at low frequency. At least the volts and frequency follow each other so if you can live with the tiny torque and power at low speed then it may be ok. The centrifugal pump is the only load I can think of that would have some sort of chance.

You would need to choose your alternator pole number to suit the motor frequency and voltage. You would need more poles on the alternator to get something like 60Hz if you are aiming for fairly standard motors.

I did test a Wadkin high frequency router motor on reduced volts from a PMA on bench test and it followed ok but it was not loaded.

If the motor load is below pull out over the whole speed range then it should work but if it pulls out you will be in real trouble and the pma may not start it at higher voltage from standstill even if off load. The choice of motor may also be important as the cage characteristics can be very strange on some motors. Some will lock on to a harmonic and crawl.

Flux

[okwindpower]

Hey Flux, good to hear from you.  You are correct in assuming that I am wanting to run a 3 phase, squirrel cage, induction motor, which indeed will be coupled to a centrifugal pump.  I know that the sizing, motor style, frequency and induction are all going to make this project "interesting" to say the least.  That is why I posed the question, to see if anyone else had even tried this.  

The beauty of this project would be a really nice wind driven well pump that would effectively use the power available to the max efficiency of the pump.  Using VFD's to operate these pumps is nothing new, and is turning out to be the way to go.  One advantage is you can purchase a less expensive 3 phase pump and operate it with a VFD using single phase power to supply the VFD.  The wind driven PMA is essentially a "wild" VFD and could well do the same job in driving the pump.

Back to the computer to do some more modelling, I guess.

Mike

[Flux]

In many ways the centrifugal pump is ideal. It follows nearer to the cube law of wind than any other thing I can think of.

As long as you choose your alternator pole number to suit the motor then it should work.

You don't have to work at 60Hz base for the motor any more than you have to do with a VFD as long as the volts/cycle works out right to keep the motor below saturation.

A 415v 50Hz motor would be happy up to about 480v at 60 Hz as long as the chosen pump kept the power within the motor rating.

There will be a minimum speed below which the pump will not reach the head so there will be a low wind speed limit and the problem could be tricky at higher heads.

If you have VF experience you will know these pump limitations.

Flux