Applied Motion STM23R-2ND - Manual (Page 18)

18
STM23R Hardware Manual 920-0056C
5/5/2015
Configuring the STM23R
Step 1: Setting the Current
To achieve maximum torque, you should set the current to 100%. But under some conditions you may want to
reduce the current to save power or lower motor temperature. This is important if the motor is not mounted to
a surface that will help it dissipate heat or if the ambient temperature is expected to be high.
Step motors produce torque in direct proportion to current, but the amount of heat generated is roughly
proportional to the square of the current. If you operate the motor at 90% of rated current, you’ll get 90% of
the rated torque. But the motor will produce approximately 81% as much heat. At 70% current, the torque is
reduced to 70% and the heating to about 50%.
Two of the small switches on the front of the STM23R are used to set the percent of rated current that will be
applied to the motor: SW1 and SW2. Please set them according to the illustration below.
Step 2: Setting Idle Current
Motor heating and power consumption can also be reduced by lowering the motor current when it is not mov-
ing. The STM23R will automatically lower the motor current when it is idle to either 50% or 90% of the running
current. The 50% idle current setting will lower the holding torque to 50%, which is enough to prevent the load
from moving in most applications. This reduces motor heating by 75%. In some applications, such as those sup-
porting a vertical load, it is necessary to provide a high holding torque. In such cases, the idle current can be set
to 90% as shown.
1 2
100%
1 2
90%
1 2
70%
1 2
50%
3
50%
3
90%