20
Figure 1.4.1 A & B: Per Phase Winding Inductance
The per phase winding inductance specified may be different than the per
phase inductance seen by your IB driver depending on the wiring configu-
ration used. Your calculations must allow for the actual inductance that the
driver will see based upon the motor’s wiring configuration used.
Figure 1.4.1A shows a stepper motor in a series configuration. In this
configuration, the per phase inductance will be 4 times that specified. For
example: a stepping motor has a specified per phase inductance of
1.47mH. In this configuration the driver will see 5.88 mH per phase.
Figure 1.4.1B shows an 8 lead motor wired in parallel. Using this configu-
ration the per phase inductance seen by the driver will be as specified.
Using the following equation we will show an example of sizing a motor
for an IB drive used with an unregulated power supply with a minimum
voltage (+V) of 18 VDC:
.4 X 18 = 7.2 mH
The maximum per phase winding inductance we can use is 7.2 mH.
Maximum Motor Inductance (mH per Phase) =
.4 X Minimum Supply Voltage
NOTE: In calculating the maximum phase inductance the
minimum supply output voltage should be used when using an
unregulated supply.
PHASE A
PHASE B
8 Lead Stepping Motor
Series Configuration
8 Lead Steppin
Motor
Parallel Confi
uration
PHASE A
PHASE A
PHASE B
PHASE B
PHASE A
PHASE B
(Note: This example also
applies to the 6 lead motor
full copper configuration and
to 4 lead stepping motors)
(Note: This example also
applies to the 6 lead motor
half copper configuration)
Specified Per Phase
Inductance
Specified Per Phase
Inductance
Actual Inductance
Seen By the Driver
Actual Inductance
Seen By the Driver
AB
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