Fisher and Paykel motors

[DarylMc]

Just reversed the motor direction and it dropped the current right back

[DarylMc]

Hi whatever
It has standard windings and 240V controller.
240V and 0.7A per phase on the motor right now.
There is a massive difference in current depending on the direction of rotation which I assume is due to the positioning of the hall sensor.

I've been using FP motor in a centrifuge for the last 8 years.
It spin dries a large basket of washed lettuce leaves at 600 rpm for one minute.
Previously I couldnt find a suitable brushless DC drive and I was running it without hall sensors from a VFD with careful tuning to allow it to grab sync at startup.
With that arrangement it had virtually zero torque at startup but once it started moving it was fine.
Despite one drive failure during that time it worked really well but I never could get it to run on anything other than the very early motor with small magnets.
I found this brushless DC drive and wanted to give it a go with a more readily available motor.
http://www.baldor.com.au/product_view.php?PROD_ID=154
All seems good now with the standard FP hall sensor.
Fantastic low speed torque and more than enough for its task.
Fingers crossed it will give a good working life.
Thanks for the reply.

[whatever]

thanks for reply, if you ever want to go to low voltage ( 48v) (you can use ebike controllers....dirt cheap) but requires reconnecting windings into parallel ( a bit of a job) thats very interesting your using it on high voltage with low amps ( exactly what it was designed for)

[DarylMc]

If anyone is interested.
With the particular Baldor drive and a FP 42 pole stator with 14 segment 56 pole rotor, I hit a limit of 430 RPM.
Rewired the stator from star to delta and now I have much more rpm available.
Still running an acceptable 1A per phase @ 600rpm with the small load of the centrifuge.
I also tried a later model FP 36 pole stator 48 magnet rotor motor expecting it to have higher rpm but it had less.
I now put this down to back emf not allowing enough current to flow in the windings.
The later model 36 pole motor with rounded iron poles was much quieter but I didnt try connecting it in delta.

Another thing I learned was to calculate the RPM of the motor, I needed to use the measured hall switch frequency and the number of magnetic poles of the rotor which for the 14 segment rotor is 56 poles and for the newer motor which has 16 segments is 48 poles.
Hope that is of interest to someone.

[whatever]

yes its of interest, one thing I noticed was you can adjust the rpm another way, you know the big plastic thread that locks the magnets onto the original axle? you can wind it out a bit and get higher rpm, as the magnets come off the stator the rpm increases, you probably loose torque but its an interesting effect

[DarylMc]

That sounds reasonable.
Less magnetic influence on the windings from the spinning rotor giving less back emf.
http://en.wikipedia.org/wiki/Counter-electromotive_force