Specifications

20 Gear Drive, Plymouth Ind. Park, Terryville, CT 06786
Tel: [phone] Fax: [phone] http://www.amci.com
CHOOSING YOUR MOTOR
A
47
Unipolar Ratings (continued)
Many motor manufactures still publish unipolar ratings
for their motors instead of bipolar ratings. Therefore, you
must convert the unipolar current rating to either the bipo-
lar series or bipolar parallel current rating to determine the
correct setting for the SD17063. Table A.1 lists the multi-
pliers to convert from unipolar to either of the bipolar val-
ues. Conversion factors for voltage, winding resistance,
winding inductance, and holding torque are also given.
As a conversion example, assume a size 34, two stack
motor has a unipolar current rating of 3.7 amps and you
will be wiring the motor to the SD17063 in parallel. The
conversion from the Unipolar to Bipolar Parallel is 1.41.
Therefore the maximum current setting for this motor is
3.7 * 1.41 = 5.2 amps.
In order to avoid confusion, AMCI publishes the bipolar
series and bipolar current ratings on all of our motors.
For your convenience, Table 2.5, Stepper Motor Specifi-
cations on page 16 lists the maximum series and parallel
currents for our motors.
Table A.1 Motor Conversion Factors
Desired Value
Unipolar
Multiplier
Bipolar Series
Multiplier
Bipolar Parallel
Multiplier
Rating
Known Value
Unipolar
or
Bipolar
Center Tap
1
Volts 1 1.41 0.707
Amps 1 0.707 1.41
Ohms 1 2 0.5
Inductance 1 4 1
Holding Torque 1 1.41 1.41
Bipolar
Series
Volts 0.707 1 0.5
Amps 1.41 1 2
Ohms 0.5 1 0.25
Inductance 0.25 1 0.25
Holding Torque 0.707 1 1
Bipolar
Parallel
Volts 1.41 2 1
Amps 0.707 0.5 1
Ohms 2 4 1
Inductance 1 4 1
Holding Torque 0.707 1 1
SM34 - 650D
0
100
200
300
400
500
600
700
800
0 1020304050
Speed (RPS)
––Torque (oz-in) ––
- - - Power (W) - - -
Parallel
6.3A
Series
3.8A
Figure A.6 SM34-650 Torque Curves
SM42 - 1250D
0
200
400
600
800
1000
1200
1400
0 1020304050
Speed (RPS)
––Torque (oz-in) ––
- - - Power (W) - - -
Parallel
6.3A
Series
6.0A
Figure A.7 SM42-1250 Torque Curves
1) “Bipolar Center
Ta p ” refers to six
lead motors that
are connected to
the drive from
center tap to one
end. In this
configuration,
only half or the
winding is used.
If the current
specification of
the motor is listed
as bipolar, and
you decide to
connect the motor
from center tap to
end, use the
Bipolar Series to
Unipolar
multipliers.