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.
| | | | | Step Pulses | | | |
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| | | C | | | | | | |
| A | | | | B | | | | | |
Phase 1
Phase 2 
Figure 4. Normal Current Profile (Half-step Mode)
