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Benefits of Written-Pole®
Single-Phase Motors
page 4
4) Simple, Robust Construction
The basic construction of a Written-Pole®
single-phase motor is similar to that of a conventional single or
three-phase induction motor. The motor frame is constructed using ductile
iron or aluminum castings for maximum durability. stator laminations and
windings are constructed using high grade electrical steel laminations and
inverter-grade copper wire and a slot insulation materials for long-term
reliability and surge resistance (long single-phase distribution lines are a
prime target for lightning strikes). The basic layout of the stator windings
is similar to a conventional capacitor start/run single-phase induction
motor with the addition of a concentrated excitation winding occupying four
slots in the stator. The rotor
construction is also similar to that of a conventional cage induction
motor with the addition of a continuous ferrite magnet layer on the
surface of the rotor. The center portion of the rotor is manufactured
using high-grade electrical steel lamination and a high resistance
induction cage constructed of carbon steel rotor bars and end-rings. The
ferrite layer is constructed using specially developed magnets, which
enable the excitation coil to alter the magnetic pole configuration as
needed during operation and is bonded to the rotor using a patented system
developed by Precise Power Corporation of Bradenton, Florida.
5) Low
Temperature Rise under starting Conditions
Since
Written-Pole® motors are generally much more efficient under starting than
conventional induction motors, current requirements and corresponding
electrical losses are reduced dramatically. Since electrical losses in the
stator windings of an electric motor are proportional to the square of
current, a typical Written-Pole® motor generates 9 times less heat under
starting than a conventional induction motor. The resulting reduction in
heat provides for improved reliability, increased starting duration and a
higher frequency of start cycles.
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