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NI SMD-7613/7614/7615/7616 User Manual
Current
The maximum supply current you need is two times the motor current. However, you will
generally need a lot less than that, depending on the motor type, voltage, speed and load
conditions. That is because the NI SMD-761x uses a switching amplifier, converting a high
voltage and low current into lower voltage and higher current. The more the power supply
voltage exceeds the motor voltage, the less current you will need from the power supply. A
motor running from a 48 volt supply can be expected to draw only half the supply current that it
would with a 24 volt supply.
We recommend the following selection procedure:
1.
If you plan to use only a few drives, get a power supply with at least twice per phase current
rating of the step motor. Example: for a motor that is rated for 2 A/phase use a 4 A power
supply.
2.
If you are designing for mass production and must minimize cost, get one power supply
with more than twice the rated current of the motor. Install the motor in the application and
monitor the current coming out of the power supply and into the drive at various motor
loads. This will tell you how much current you really need so you can design in a lower cost
power supply.
Table 1 lists the relevant specifications for suggested motors. Please consider this information
when choosing a power supply.
Table 1.
NI SMD-7613/7615 Power Supply Current
Motor
Holding Torque
Drive
Current
Setting (A)
Resistance
(
Ω
)
Inductance
(mH)
Rotor
Inertia
(g
· cm
2
)
oz
·
in
kg
· cm
ST11-1
7.0
0.50
1.2
1.4
1.4
8
ST11-2
15.0
1.08
1.2
2.0
2.6
18
ST14-1
26.0
1.87
1.2
4.3
5.5
20
ST17-1
31.4
2.26
1.6
2.1
2.8
35
ST17-2
51.0
3.67
2.0
1.7
3.6
54
ST17-3
62.8
4.52
2.0
1.7
3.0
68
ST23-1
76.6
5.52
3.4
0.7
1.4
120
ST23-4
177
12.7
5.0
0.4
1.2
300
ST23-6
264
19.0
5.0
0.5
1.6
480
ST23-8
354
25.48
6.0
0.5
2.2
750
ST24-1
123.2
8.87
3.36
0.73
1.6
260
ST24-2
177
12.74
4.8
0.43
1.1
450
