22
Rev. 1.0
8/26/2015
TSM11 Hardware Manual
4.4 Drive/Motor Heating
Step motors convert electrical power from the driver into mechanical power to move a load.
Because step motors are not 100% efficient, some of the electrical power turns into heat as it
passes through the motor. The amount of heating is not so much dependent on the load being
driven as on 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 occurring to the
motor.
A step motor typically reaches its maximum temperature after 30 to 45 minutes of operation. A
motor that runs for one minute and then rests for one minute is said to have a duty cycle of 50%.
Five minutes of running and five minutes of rest is also a 50% duty cycle. However, one hour of
running and one hour of rest has the effect of 100% duty cycle as the motor will reach full and
possible excessive temperature during the first hour. The actual temperature of the motor depends
on how much heat is conducted, convected or radiated out of it.
The curves below result from measurements 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. Results may vary.
0
20
40
60
80
100
0
10
20
30
40
50
%
D
ut
y
C
yc
le
Speed (RPS)
TSM11 Max Duty cycle vs Speed
24V 1.5 Amps @Ambient of 40
°C
TSM11-
□
Duty Cycle
0
30
60
90
120
150
180
0
10
20
30
40
50
Te
m
pe
ra
tu
re
(
℃
)
Speed (RPS)
TSM11 Temperature vs. Speed
24V 1.5Amps @Ambient of 40°C
TSM11-1 Temp
TSM11-2 Temp
TSM11-3 Temp
