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Explanation of Size and
Winding Parameters
- Continuous Torque
- The motor is capable of developing
this torque on a continuous basis with no heat
sinking from the stator mounting mechanics.
The motor will reach 135C at room temperature
(approximately 185 C at 71 C ambient) under
these conditions. In actual applications, there
is large heat sinking available from the stator
mounting allowing higher continuous torque ratings.
This rating is therefore very conservative.
- Peak Torque
- A torque 2.5 times the continuous
ratings. The motors can achieve these levels
for short periods with no heat sinking from
the stator mounting mechanics. The wire current
handling capability and the magnetic saturation
of the steel have all been considered in this
rating.
- Peak Power -
The Peak current squared times the motor resistance
at 20 C.
- Km - Motor Constant
- A figure of merit which characterizes
the size of a motor with respect to the amount
of torque vs amount of power available. It is
mathematically the peak torque divided by the
square root of peak power or it is the torque
constant (Kt) divided by the square root of
motor resistance (R).
- Theoretical No
Load Speed - The speed at which
the motor will operate when Voltage Peak Torque
is applied to the motor with no external motor
load applied. There are magnetic and bearing
drags which will cause the motor to run a bit
lower than this published figure.
- Temp Rise Per
Watt - The TRPW values are experimentally
arrived at and are the results of a stable temperature
rise due to a steady power dissipated in one
phase of the motor while suspended in air with
no forced air cooling or conductive paths. This
therefore represents the worst case scenario
and in actual applications will be less than
the published values.
- Poles -
The number of poles has been chosen to keep
the circular magnetic paths of each motor the
same regardless of motor diameter. This standardizes
the thickness of back irons and ensures a good
sinusoidal BEMF wave-form.
- Cog Torque -
The motors cogging torque is zero due to the
absence of lamination teeth and the uniformity
of the magnetic paths with respect to angle.
There is some drag torque associated with magnetic
hysteresis and viscous damping associated with
all PM motors brush or brushless.
- Inertia - The
moment of inertia about the axis of rotation.
Multiply by 0.00706 to convert to Kgm-m2.
- Weight -
The weight of the combined rotor and stator
without leads.
- Voltage Peak
Torque - The nominal voltage required
to generate the peak torque when the winding
temperature is 20 C. It is nominally Peak current
time R. Since the motor torque is proportional
to current, as the motor heats the resistance
increases causing the current to drop for a
constant voltage source. This should be considered
in designing the drive system.
- Peak current
- The current required to generate
the Peak Torque of the motor. It is Peak voltage
divided by motor resistance at 20C.
- Kt - Torque
Constant - The amount of torque
developed for a given
current. It is true-independent of motor speed.
- R - Motor resistance
- The 20C resistance of each phase
of the motor.
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Phone: |
(631) 231-9100 |
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Fax: |
(631) 231-8375 |
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