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Benefits of Written-Pole®
Single-Phase Motors
The
following summary provides an overview of benefits of Written-Pole®
single-phase motors. Based on
Written-Pole® technology, a patented concept developed by Precise
Power Corporation, these innovative single-phase motors offer many
advantages over conventional single or three-phase electric motors.
1) Low Starting Current
requirements
The most significant characteristic of V
single-phase motors is their low inherent starting current.
Written-Pole®
single-phase motors exhibit starting current requirements
ranging from 1.7 to 3 times their rated current, unlike conventional
induction motors (single or three-phase) that have typical starting
currents ranging from 6 to 9 times their rated current. A typical
Written-Pole®
single-phase motor has a starting current, comparable
to a conventional single-phase motor one-fourth its rating, dramatically
increasing the maximum rating that may be started on rural single-phase
distribution systems.
The low starting current of
Written-Pole®
single-phase motors is a by-product of their unique
design that combines the starting characteristics of a permanent magnet hysteresis motor (the surface of the rotor is covered with a continuous
layer of ferrite magnet material) with those of a high slip, high power
factor, NEMA Design D induction motor (the rotor contains a high
resistance induction cage that uses steel rotor bars and end-rings to
increase the electrical resistance of the rotor under starting). Upon
reaching 75 to 80% of its rated speed, an excitation coil in the stator
winding is energized (using AC power at line frequency), creating a strong
alternating magnetic field that tailors the magnetic pole configuration of
the ferrite layers for optimum starting torque and acceleration. The
excitation coil is de-energized when rated speed is attained allowing the
motor to operate as an energy efficient, synchronous permanent magnet
motor.
Since s
Written-Pole®
single-phase motor's low starting current is attained
without reduced voltage starting, the design does not sacrifice starting
torque as is common with three-phase motors started using reduced voltage
devices designed to limit starting current. Not only does this simplify
the design and construction of the motor, but it also enhances the
usability of
Written-Pole® single-phase motors under a variety of applications.
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