(c) copyright 2004-2007 www.stappenmotor.nl
These rules are rather simple, but they are correct to a certain extent.
Most steppermotors are electromotors of the hybride type. These are the strongest steppermotors with a very good price/performance ratio. The number of steps a steppermotor can execute with a fullstepdriver is usual 200. At every fullstep the shaft of the steppermotor rotates 1.8 degree and holds there. With a microstep driver the steps of a steppermotor are divided in so called microsteps. If one use's a microstepdriver with 40 microsteps, the shaft of the same steppermotor has 200 * 40 = 8000 posible position's. With every micro step the shaft of the steppermotor rotates 1.8 / 40 = 0.045 degree's. So a steppermotor doesn't need a feedback ( open system ) unlike a servomotor.
Provided there is enough space, use a long thin steppermotor, instead of a short big one ( with the same torque ). A long thin steppermotor has a lower rotorinertia, and so accelerates faster. A steppermotor with a higher current is better than one with a low current. The higher the current, the lower the selfinduction of the steppermotor, so the less E.M.K. the steppermotor produces at higher rotation. So the steppermotor has a better torque at high speeds. All our stepermotors can be specified with a high current on request. The higher the voltage of the steppermotor-driver, the better the torque at higher speeds will be. If a steppermotor at high speeds misses steps, there is little point in increasing the current. This only increases the torque at low speeds, not at high speeds. Increase ( if posible ) the voltage of the steppermotor-driver. A steppermotordriver with microstep is better than one with full or half step.With microstepping, the steppermotor makes smaller steps, and so doesn't fibrate as much as a full step driven steppermotor. The complete system doesn't get that much fibration from the steppermotor. The only advantage of a full steppermotor-driver is the torque. At full step the torque is higher, as the steppermotor gets driven by all the coils. A steppermotor with 8 wires can be used with both unipolair and bipolair systems. Also there is the posibility to connect the coils in series ( low current ) and parallel ( high current, but also better torque at high speeds ). Use the coils parallel. The current is than higher, but also the torque at high speeds. When you use a unipolaire steppermotor-driver, a part of the coils isn't used, so there is always a loss in torque, both at low and at high speeds. This can be compensated for by increasing the current somewhat, but it can never completely be compensated for.
The ( maximum ) speed of a steppermotor depends on serveral things. First there is the start-stop speed of the steppermotor. This is the maximum number of steps a non-rotatingl standing steppermotor can follow from one moment to the other. This is influenced by the rotor inertia and of cource by the system. Also the voltage the steppermotor-driver can supply to the steppermotor is of influence. Wenn the steppermotor turns it can accelerate more, up to the point where the steppermotor generates a voltage of its own that counteract with the voltage supplyed by the steppermotor-driver. At that point there is no more acceleration posible, and the torque is zero. So the maximum speed is dependent of the voltage suplied to the steppermotor-driver, as the steppingmotor needs to turn faster to supply a countervoltage as large as the powersupply.
The start-stop frequentie is that frequentie which the steppermotor can follow without the need for a acceleration or deceleration. This is also called the pull-in frequentie.
The pull-out frequentie is that frequentie that the steppermotor can follow, but only with a acceleration or deceleration.
The maximum speed is for a large part dependent on the voltage the steppermotordriver can supply. As the steppermotor turns, it produces the counter-voltage and this is responsible for the drop in torque as the steppermotor starts to turn.
This is a rather simple way of looking at steppermotors, but for a beginner this is a good way to start.
(c) copyright 2004-2007 www.stappenmotor.nl