HD65 & HD130 STEPPER DRIVES USER GUIDE 13
Current Profile
Setting (Half-step
Mode)
In the half step mode, a two-level current profile is used at low
speeds to equalise torque on alternate steps. Figure 4 shows this
current profile with A and B representing the two-phase-on condition,
and C the one-phase-on condition. When two phases are energised
the current levels are 6.5A and 13A for the HD65 and HD130 drives
respectively. These current levels are increased in the one-phase-
on condition to 9A (HD65) and 18A (HD130) to help maintain the
torque on intermediate steps.
The function of the square-off circuit is to maintain torque output in
the middle speed range where the average motor current is falling
off due to winding inductance. The current profile is "squared off" to
the one-phase-on level at 3200 half steps/sec. The square-off
speed is determi-ned by R2 on the drive motherboard. The standard
value is 33K, and halving the resistor value will double the square off
speed. Do not change this resistor value without first consulting
Digiplan.
Turning on switch 5 will give permanent square-off. This will give a
significant increase in low speed torque, but will also increase motor
noise and temperature rise. This setting should therefore be used
with discretion. Square-off is logically inhibited at standstill to
prevent overheating. Turning on switch 0 will have the effect of
permanently inhibiting square-off.
When using a microstepping drive (HD65M or HD130M), switch 5
should be in the "off" position. Note that selecting permanent
square-off in a micro-step mode would effectively return the drive to
the full step current profile.
AC
B
Phase 1
Phase 2
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Step Pulses 9
Figure 4. Normal Current Profile (Half-step Mode)