Low-speed synchronous motor is the continuous rated synchronous motor in which quick bi-directional rotation is possible. The basic construction of low-speed synchronous motor is the same as that of stepping motors. Since they can be driven by an AC power supply, they are sometimes called AC stepping motors.
Low-Speed / Synchronous Rotation
The motor rotates at a speed proportional to and accurately synchronized with the frequency of the power supply. A fluctuation in load does not affect the rotation speed.
At 50 Hz 60 r/min (30 r/min)*.
At 60 Hz 72 r/min (36 r/min)*.
Superb Starting, Stopping and Reversing Characteristics
If operated within the permissible load inertia, the motor can start, stop and reverse within 1.5 cycles (0.03 sec at 50 Hz, 0.025 sec at 60 Hz) of power supply frequency.
The motor can be stopped instantly by turning off the power supply. The stopping accuracy within the motor's permissible load inertia is ±10°. When a precision switch is used, simple and precise positioning is possible.
Since a permanent-magnet, multi-poled rotor is used, the motor has holding torque even when the motor is not energized. When used with a gearhead, comparatively high holding torque can be utilized.
When, at motor standstill, a DC power supply is used, large holding torque almost equal to that of a stepping motor can be produced.
Constant speed can be maintained even during lowering operations. Low-speed synchronous motors are suitable for application, such as an elevator system, whereby vertical operation at the constant speed is required.