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NI ISM-7400 User Manual
Reference Materials
Torque-Speed Curves
Figure 27.
Torque Curve for NI ISM-7400
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.
The drive electronics of the NI ISM-7400 also dissipate power. The heat produced by the
electronics is dependent on power supply voltage and motor speed.
The following figure show the maximum duty cycle versus speed for each motor at commonly
used power supply voltages. Refer to these curves when planning your application. Charts
depicting typical power dissipation are also provided for use in planning the thermal design of
your application.
A step motor typically reaches maximum temperature after 30 to 45 min of operation. Running
the motor for one minute and then idling for one minute results in a 50% duty cycle. Running
the motor for five minutes on and five minutes off also results in 50% duty. One hour on and one
hour off results in 100% duty because the motor will reach full and possibly excessive
temperature during the first hour of use.