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NI SMD-7611/7612 User Manual
Step 2: Fine Tuning the Motor Current
The maximum current for the motor is set when the rotary switch is configured to select a motor.
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%.
Switches 1 and 2 on the front of the SMD-7611/7612 drive are used to set the percent of rated
current that will be applied to the motor. Refer to the table below to configure the switches.
ST23-6
Parallel
5
264
480
6
ST24-1
4 leads
3.36
123
280
7
ST24-2
4 leads
4.8
177
450
8
ST24-3
4 leads
4.8
354
900
9
ST34-2
Parallel
8
507
1400
A
ST34-5
Parallel
8
965
2680
B
ST34-8
Parallel
8
1439
4000
C
ST34-1
Parallel
7.56
396
1100
D
ST34-4
Parallel
7.56 series
849
1850
E
Table 5.
Configuring Current on Switch 1 and 2
100%
90%
80%
70%
Table 4.
SMD-7612 Motor Specification Table (Continued)
Model
Number
Wiring
Drive Current
(A), peak of
sine
Holding
Torque (oz-in.)
Rotor
Intertia
(g-cm
2
)
Switch
1 2
1 2
1 2
1 2