Applied Motion STM23C-3CE - Manual (Page 44)

Drive/Motor Heating
Step motors convert electrical power from the driver into mechanical power to move a load. Because step motors
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 voltage. There
are certain combinations of speed and voltage at which a motor cannot be continuously operated without damage.
We have characterized the STM23 drive+motors in our lab and provided curves showing the maximum duty cycle
versus speed at commonly used power supply voltages. Please refer to these curves when planning your applica-
tion.
Please also keep in mind that a step motor typically reaches maximum temperature after 30 to 45 minutes of opera-
tion. 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.
Please use the curves below, which show the motor body temperature, to determine the maximum duty cycle of
the STM23 drive+motors under various conditions.
STM23-2 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
C
yc
le
12V Duty Cy c le
24V Duty Cy c le
48V Duty Cy c le
65V Duty Cy c le
Maximum Duty Cycle vs Speed
44
STM23 Hardware Manual
920-0021F
2/14/2012