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WARNING! Do not connect or disconnect the AC power leads
or the motor leads with power applied!
11
MOTOR
SECTION 8.1
MOTOR SELECTION
The IM481H is a Bipolar driver which works equally well with both Bipolar and Unipolar
motors, ( i.e. 8 and 4 lead motors and 6 lead center tapped motors (see section 8.2,
Connecting the Motor)).
To maintain a given set motor current, the IM481H chops the voltage using a constant
chopping frequency and a varying duty cycle. Duty cycles that exceed 50% can cause
unstable chopping. This characteristic is directly related to the motor’s winding
inductance. To avoid this situation, it is necessary to choose a motor with a low winding
inductance. The lower the winding inductance, the higher the step rate possible.
The maximum per phase motor inductance for the IM481H is calculated as follows:
Max. per Phase Inductance (mH) = 2 x Supply Voltage ÷ 10
NOTE: In calculating the maximum phase inductance, when using an unregulated
power supply, the minimum supply output voltage should be used.
Since the IM481H is a constant current source, it is not necessary to use a motor that is
rated at the same voltage as the supply voltage. What is important is that the IM481H is
set to the motor’s rated current.
The higher the voltage used the faster the current can flow through the motor coils. This in
turn means a higher step rate. Care should be taken not to exceed the maximum voltage
of the driver.
Therefore in choosing a motor for a system design, the best performance for a specified
torque is a motor with the lowest possible winding inductance used in conjunction with the
highest possible driver voltage.
SECTION 8.2
CONNECTING THE MOTOR
Phase A of the Stepping Motor is connected between pins 1 and 2. Phase B of the
Stepping Motor is connected between pins 20 and 21. The following drawings in figure 4
illustrates the connection of 4,6, and 8 Lead Stepping Motors to the IM481H Driver.
NOTE: To reduce the transmission of EMI from the motor cables, a twisted pair
sheilded cable is recommended if the driver to motor cabling is in excess of
one foot. Motor leads should not exceed 100 feet. Refer to Section 10,
Recommended Wiring, for further information.
NOTE: The physical direction of the motor with respect to the direction input will
depend on the connection of the motor windings. To reverse the direction of
the motor with respect to the direction input, switch the wires on either
phase A or phase B outputs.