Motor Wiring

Figure 81: Toque speed characteristics of series and parallel wired stepper motors

подпись: figure 81: toque speed characteristics of series and parallel wired stepper motors

The stepper motor used is an 8-wire 2-phase motor, enabling it to be wired in either a bipolar series or bipolar parallel configuration. Because series wired coils have greater inductance they tend to produce more torque at lower speeds, while at higher speeds the larger inductance leads to a greater resistance to current and consequently less torque compared to parallel wired coils, as illustrated by the generic characteristic shown in Figure 81.

Motor Wiring

SPEED

For the application of driving the displacer the maximum torque is required at low speeds to accelerate the load quickly. For this reason it would be ideal to wire the motor in the bipolar series configuration as shown on the left in Figure 82, however when tried in practice it was found that the motor would stall at relatively low speeds under this configuration, meaning that the bipolar parallel configuration (pictured right in Figure 82) was instead adopted, which was found to allow much greater operating speeds necessary for fast actuation of the displacer.

5 o 5 ф

 

BI-POLAR Series (6 Leads) BI-POLAR Parallel (8 Leads)

 

Figure 82: Wiring diagrams for motor phases, bi-polar series (left) and bi-polar parallel (right)

 

Motor Wiring

After connecting the coils in parallel there are 4 wires that protrude from the motor. These are connected to the Phase A +, Phase A -, Phase B + and Phase B — outputs from the driver. In addition there is a shield wire that connects to the grounding point on the motor frame and to the shield connector at the driver.

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