turning an alternator into a motor?

[mobile_bob]

alternators will not run simply by applying 3 phase power to the stator and a current to the field (rotor), they will just sit there and do the jitterbug

they will however run as induction motors, although with very poor efficiency
all you have to do is short the field windings at the brushes and apply the three phase power and off to the races it will go... just not with a lot of power.

these sensorless ESC units sense the shift in inductance as the poles pass each other and trigger the phase pulse, this provides for sync/timing and increased torque.

the sensor type ESC of course uses a sensor(s) to determine the pole position relationship, and in doing so allows for control to the phase timing.

the amount of field current then is used to dial in the rpm, and some other characteristics such as power factor.

thanks for the links btw...

some of these are priced low enough to take a shot with and try it out.

bob g

[buickanddeere]

Glort:

that is exactly what i have in mind!  you win the cigar! 

EBI-WPO:

i have tried to feed the stator three phase power and it just doesn't work as expected when i energize the rotor field, it just sits there and pulsates/growls

now when i put a reostat across the field/rotor the thing will motor, just not with much power
as it makes for a very inefficient induction motor with its solid rotor poles...

Cornelius and Bruce, i will check out the two sources and see what they have to offer.

thanks
bob g

Need to enegize the rotor with approx 6V DC. Can't leave the rotor field open. It will just become the secondary of a transformer. 60Hz is pretty slow to drive an automotive alternator with.

[bschwartz]

Thob,
".........he frequency of the alternator (in Hz) was almost exactly the RPM of the engine.  That made for an easy tachometer"

I have a 6.5 Turbo Chevy Suburban that uses the alternator for the tach.  A common problem is people replacing a bad alternator with a gas motor version (different size pulley) and then wonder why their tach isn't reading correctly