AC Motors: Design Considerations

Synchronous Motors

Power supply AC
Driver electronics need No
Speed accuracy High Not effected by load torque
No closed loop speed control need
Speed control No Not possible
Speed fixed by mains supply frequency
Position control No Not possible — only by limit switches
Overloadablity / load inertia Low High start torque or peak load torque
Able to accelerate high load inertia
Lifetime High Only little reserve for peak load torque
Can’t accelerate high inertia
Speed range [rpm] 250...36000 Limited by bearings
Depends on lateral force
Efficiency 15...45% Depend on pole number and mains frequency
Power vs. size Low Higher for 2-pole motor
Winding thermal protection No need Inductance protected
(if winding designed for 100% duty cycle)
Load sensing Difficult Load has little impact on current
Stalling permissible Yes If winding designed for continuous duty cycle
Electromag.interference EMI Not Critical No brushes
Braking/Holding torque Low Detent torque (when power switched off)
Max.output power from JE [W] 14 Approximately, for short time duty cycle S2
Linear motors from JE Yes

Shaded Pole Motors

Power supply AC Mains supply
Driver electronics need No
Speed accuracy Low Effected by load torque
Speed at rated point about 2600 rpm at 50Hz
Speed control No
Position control No
Overloadablity / load inertia Low Little reserve to max .torque
Lifetime High Limited by bearings
Depends on lateral force
Speed range [rpm] 2600 Rated speed at 50Hz
Efficiency 20% At rated point (14% at ½ rated point)
Power vs. size Low
Winding thermal protection Possibly
Load sensing Medium Current rises with load, but less than DC mot
Stalling permissible Yes
Electromag.interference EMI Not Critical
Braking/Holding torque Very Low No permanent magnets
Max.output power from JE [W]
Linear motors from JE No