Applied Motion STM23R-2ND - Manual (Page 24)

24
STM23R Hardware Manual 920-0056C
5/5/2015
Heating
Step motors convert electrical power from the driver into mechanical power to move a load. Because step mo-
tors are not perfectly efficient, some of the electrical power turns into heat on its way through the motor. This
heating is not so much dependent on the load being driven but rather the motor speed and power supply volt-
age. There are certain combinations of speed and voltage at which a motor cannot be continuously operated
without damage.
The drive electronics of the STM23R also disspate power. The heat produced by the electronics is dependent
on power supply voltage and motor speed.
We have characterized the STM23R in our lab and provided curves showing the maximum duty cycle versus
speed for each motor at commonly used power supply voltages. Please refer to these curves when planning
your application. Charts depicting typical power disspation are also provided for use in planning the thermal
design of your application.
Please also keep in mind that a step motor typically reaches maximum temperature after 30 to 45 minutes of
operation. If you run the motor for one minute then let it sit idle for one minute, that is a 50% duty cycle. Five
minutes on and five minutes off is also 50% duty. However, one hour on and one hour off has the effect of
100% duty because during the first hour the motor will reach full (and possibly excessive) temperature.
The actual temperature of the motor depends on how much heat is conducted, convected or radiated out of
it. Our measurements were made in a 40°C (104°F) environment with the motor mounted to an aluminum plate
sized to provide a surface area consistent with the motor power dissipation. Your results may vary.
Maximum Duty Cycle
STM23R-2 Max Duty cycle vs Speed
5 Amps @Ambient of 40°C
Mounted to a 6.4" x 6.4" x .25" Aluminum Plate
0
20
40
60
80
100
0 10 20 30 40 50
Speed (RPS)
%
D
ut
y
Cy
cl
e
12V
24V
48V
65V