NOISE
AND VIBRATION
The Hysteresis Synchronous motor consists of a wound stator
and a rotor of uniform high permeable material. Having a
smooth rotor of homogenous material, the noise and vibration
produced is inherently low. Since there are no pole faces
or saliencies, the magnetic path is of constant permeability,
thus eliminating the magnetic pulsations which are the major
cause of noise in the salient pole type.
TORQUE
The torque of the motor is uniform due to the homogenous
rotor and constant permeability. There is no variation in
torque throughout a revolution. The availability of new
materials and designs have increased the torque and horsepower
values into the one horsepower range.
SPEED
The speed of the Hysteresis Synchronous motor is determined
by poles and line frequency as given in the formula:
| Synchronous
RPM= |
120
X Line Frequency
Number of Poles |
This
speed is constant regardless of load variations within the
rating of the motor. With a variation of load, however,
the rotor will assume a new load angle dependent on the
load variation.
Where large load variations or fluctation of line voltage
occur, the stabilized Hysteresis motor can be used to reduce
hunting. This motor type is described in more detail here.
The rotor of the Hysteresis motor, not requiring pole saliencies
allows for the design of low speed motors as well as multi-speed
motors using the same rotor. Five speed motors and low speeds
of 600 rpm, are standard items. Variations to the number
of speeds and lower speeds are available in special designs.
LOAD INERTIA
The Hysteresis Synchronous motor is capable
of synchronizing high inertia loads, being unaffected by
load inertia, it need only be powerful enough to drive the
frictional component of load. The Hysteresis Synchronous
motor can pull into synchronism high inertia loads that
would require a salient pole motor several times its horsepower
rating.
STARTING TORQUE
In the Hysteresis Synchronous motor, the starting
torque is constant throughout 360° of rotor position.
Where uniform starting torque or constant tension is required,
Hysteresis Synchronous motors, due to the absence of cogging,
have been used successfully as torque motors.
PHASING
The rotor of the Hysteresis Synchronous motor,
having no pole saliencies, will lock in phase in any of
the 360° of rotor rotation.
In applications where definite phasing is required, the
polarized Hysteresis motor is recommended. This type of
motor has one-half the "lock-in" points of the
salient pole Induction motor. This motor type is described
in more detail here.
SUMMARY
The
Hysteresis Synchronous motor characteristics are:
- Low
noise and vibration
-
Constant speed regardless of load and voltage variation
within motor rating
-
Capability of synchronizing high inertia loads Uniform
starting torque
-
Can be wound for lower speed and greater number of poles
than is practical with salient pole induction type motors
-
Can be provided as multi-speed motor
- Will
lock in at any position with respect to line voltage
