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The
proposed Marine Propulsion Motor utilizes the brushless DC
Motor technology to achieve its high performance rating at
high efficiency. Further performance improvement is achieved
by applying "Slotless" Brushless design technology.
Conventional
Marine motors are brush type motors with wound rotors and
surrounding permanent magnet fields. While such motors are
more economical to build and are simple to control, they tend
to be quite inefficient under high loads. They do not dissipate
heat as well as brushless motors which have windings outside
the permanent magnet segments and thus a relatively short
thermal dissipation path to the surrounding water. EXHIBIT
A provides a more comprehensive comparison of the three
motor technologies and points out the advantage of using the
"Slotless" version in this application.
EXHIBIT
A: Permanent Magnet Motors - Key Characteristics
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SLOTLESS
BRUSHLESS DC |
CONVENTIONAL
BRUSHLESS DC |
BRUSH
TYPE PERMANENT
MAGNET DC |
| A.
STATOR |
Ringtype
toothless laminations in stack. Windings consolidated
into annular ring and bonded mechanically and thermally
to ID of stack. Winding pattern and number of poles variable.
Conventional lead attachment, lacing, tying, and head
forming followed by varnish impregnation. |
Multiple
tooth laminations from precision blanking tools, aligned
and stacked. Windings located in slots. Winding pattern
and number of poles determined by lamination design. Conventional
lead attachment, lacing, tying, and head forming followed
by varnish impregnation. |
Solid
magnetic steel cylinder with arc type magnets bonded to
ID of cylinder. Usually corrosion protection on surfaces.
Cylinder usually becomes motor housing. |
| B.
ROTOR |
Arc
(or slab) magnets bonded to a cylindrical (or square)
magnetic steel core with hole for shaft of custom design
and material, number of poles variable. Usually hi-energy
magnets. |
Same
construction as slotless rotor but smaller diameter (less
magnet area) for a given motor OD. |
Toothed
laminations from precision tooling and pressed on custom
shaft. Windings in slots and terminated at commutator
pressed on shaft in a correct relationship to the laminations.
Windings are commutated through brush assemblies in contact
with commutator. |
| C.
HOUSING |
In
direct contact with stator and winding for superior heat
dissipation. |
No
functional differences from slotless motors. |
Requires
accommodation for brushes and holders. Usually open construction
for cooling. |
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SLOTLESS
BRUSHLESS DC |
CONVENTIONAL
BRUSHLESS DC |
BRUSH
TYPE PERMANENT
MAGNET DC |
| A.
PERFORMANCE |
Improvement
in life, noise, heat rise, efficiency, and controllability
over other conventional brush type PMDC motors.
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Inherently no tooth "cogging".
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Low torque ripple for smooth lo-speed operation.
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High efficiencies achievable.
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Low inductance, low time constant, for high-speed
operation.
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Improved heat dissipation from windings.
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Higher power levels per unit weight.
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| B.
ECONOMICS |
- Low
tooling costs, design flexibility.
- Broader
tolerance construction due to large magnetic gap,
no precision teeth.
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Potentially less expensive stator fab process compared
to conventional BLDC and AC motors.
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Stator fab process similar to AC stator construction
and already highly mechanized.
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Less magnetic material required to achieve a given
torque due to smaller magnetic gap.
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Currently most economical to build. High volume, low
labor equipment available.
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No electronics required to operate.
- Speed
control electronics less expensive compared to conventional
BLDC and AC motors.
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The
OEC motor mechanical design was developed after years of experience
in designing under water motors for military, industrial,
and commercial applications. All joints and connections are
made behind static "O"ring type seals except, of
course, the rotor shaft seal, which is a specially selected
dual rotary seal with a design life of several years.
The
motor electronic driver is mounted so as to achieve a short
thermal path for the power handling devices through the aluminum
housing to the water. It is mounted in the "nose"
of the motor under an aluminum cover. A multi-conductor cable
from the driver "module" extends up the mounting
shaft to a control board mounted on an aluminum casting housed
in a thermoformed ABS housing. The housing includes a detachable
(for cable remote control) "box" that contains,
a safety power switch, FWD, REV, OFF selector switch, a levered
speed control potentiometer, and a digital panel meter for
battery voltage or motor RPM readout. Also an over temperature
indicator lamp warns the user that the motor is overheated
and the power is automatically reduced to half speed until
the temperature recedes to a safe limit.
Power
is fed down the mounting shaft to the motor though high current
carrying conductors to minimize voltage drop between batteries
and motor. A reverse voltage protection feature will not allow
the motor to start if the batteries are connected with the
wrong polarity.
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Our new motors are sealed for freshwater and saltwater use!