2-2
Gather the Following Information
• Power rating from motor nameplate in watts, kilowatts, or
horsepower
• Speed rating from motor nameplate in rpm or rps (radians per
second)
• Motor inertia and load inertia in kg-m
2
or lb.-ft.
2
• Gear ratio (GR) if a gear is present between the motor and load
• Motor shaft speed, torque, and power profile of the drive application
Figure 2.1 shows the speed, torque, and power profiles of the drive as a
function of time for a particular cyclic application that is periodic over t
4
seconds. The desired time to decelerate is known or calculable and is
within the drive performance limits. In
Figure 2.1, the following
variables are defined:
ω(t) = Motor shaft speed in radians per second (rps)
N(t) = Motor shaft speed in Revolutions Per Minute (RPM)
T(t) = Motor shaft torque in Newton-meters
1.0 lb.-ft. = 1.355818 N-m
P(t) = Motor shaft power in watts
1.0 HP = 746 watts
ω
b
= Rated angular rotational speed
ω
o
= Angular rotational speed less than ω
b
(can equal 0)
-P
b
= Motor shaft peak regenerative power in watts
ω
2πN
60
----------=
Rad
s
---------
Rad
s
---------
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