I’m looking to get some clarification on what is meant by the phase of a stepper motor. What I’m gathering is that a higher phase numbered stepper(i.e. 5 vs. 2) will produce higher resolution of steps and thus higher precision, but what is meant by the actual phase? I’m assuming that the phase is referring to the current drawn in through each coil, so a 2 coiled stepper is equivalent to saying 2 phase?
Secondly, in regards to motor drivers, if a motor is rated at 2amps per phase, does the motor driver need to accommodate at minimum 4 amps? or is the alternation of power through the motor coils keeping the overall current through the motor at closer to 2 amps?
A stepper motor has several windings. Two is the most common. Each winding is basically turned on and off (there are variations, but that is essentially what is happening.) So a winding is driven with a “waveform” that is on for some amount of time and off for some amount of time. If the windings were turned on and off at the same time the waveforms would be said to be “in phase.” If one was turned off the entire time the other was turned on they would be called “out of phase” or a phase difference of 180 degrees (waveforms are based on a complete circle of 360 degrees.) However, the motor wouldn’t work or at best would work poorly. So, the power to the windings is staggered some percentage, usually based on the number of windings, so that power is applied to one winding, then the next, then the next, and so on. Sometimes they overlap with two on at a time. That is the general definition of “the phase.”
However, it gets confusing because the windings, or part of a winding, is often referred to as a “phase” of the motor, hence “two phase” or “five phase” motors. But what that really means is that you need to stagger the applied waveforms by that many steps of phase. For instance, the “phases” of a five phase motor would be staggered by 360/5 or 72 degrees apart on the waveform.
In general, the number of phases and the resolution of the motor are independent. Although higher-phase motors will often be built with higher resolution. There are other benefits, too, but as a general rule it doesn’t make much difference.
Just to confuse things more, a 2 phase and a 4 phase motor both have two windings and can sometimes be used interchangeably.
Any stepper should be rated with the number of steps per revolution. That will be independent of the number of phases.
Your question about the current drawn is a bit confusing. Current will be drawn through a winding whenever that winding is on. To put it another way, when that phase is “active.” But the AMOUNT of current doesn’t depend on the number of phases.
For your second question, motor drivers are usually rated “per phase.” A motor driver will typically say something like “2 amps per phase.” Sometimes the marketing people get creative and say " 4 amp driver" and you have to read a bit deeper to find they mean 2 amps per phase.
For your second question, motor drivers are usually rated “per phase.” A motor driver will typically say something like “2 amps per phase.” Sometimes the marketing people get creative and say " 4 amp driver" and you have to read a bit deeper to find they mean 2 amps per phase.
Maybe I can clarify my question a bit. Since the windings are typically alternating in on and off states, I’m thinking only one of the windings is powered at a given time, so a 2 phase motor with 2amps/phase, should in theory only be drawing 2 amps at any time if the windings are alternating correctly. If there is some partial overlap between the timing of the windings being on, there would likely be more current drawn right?
So when applying a motor driver to a motor such as this, is it appropriate to use a driver that’s rated for 4 amps total to account for any overlap, or is a 2amp rated driver ok to use?
The amount of current per phase is what is important. if each phase/winding draws 2 amps then each phase of the driver must be rated for 2 amps. that applies whether there is any overlap or not. The totals (motor or driver) aren’t really important or even relevant.
