Here's the disconnects:
Even if you could put a several thousand volt driver on the motor and run an amp through it no matter what, it's torque wold still drop off. The hysteresis and loss in the magnetic materials used in the motor are the limit here. As the frequency goes up their losses go up as well. All of your added input simply goes to heat. The easy way to look at that is the angle between the voltage and current. You can directly measure what's going on.
In a stepper the torque starts off at the holding torque and pretty much just drops as rpms (or frequency) goes up. Your "dynamic torque" has an upper bound in the static torque. That's what makes static torque a very important parameter on a motor. That's why you can always find it specified.
A motor is a *very* slow thing. Compared to electronics motors simply don't move. Put in a more technical fashion a stepper motor's torque drops off as you try to run it faster. You could get the current up to spec in a nanosecond and the motor would just sit there for a *long* (in nanoseconds) time. You have acceleration and jerk limits on controllers for exactly this reason. You can't take a motor from zero to 10 rpm in zero time. You *slowly* go from static DC to stepping. The only time you ever have high voltage on a stepper is when you are running high RPM's. Except on some very unusual Delta's we just don't run high rpm's.
You can go through the acceleration math and the feed rate math to confirm all of this.
A simple example:
Motor is at rest.
I want to go 10 rpm
I immediately step at 10 rpm
Motor slips
Motor is at rest
I want to go 10 rpm
I slowly accelerate to 10 rpm
Motor does not slip.
In this case "slow" is in electrical terms. I'm accelerating the motor as fast is it can in mechanical terms. On an 200 mm travel at max 200 mm / sec, I spend 1/4 of my time accelerating or slowing down. 250 ms is a *long* time in electrical terms. As the motor starts and finishes it's at low RPM's. Low RPM's mean low drive frequencies. Low drive frequency means that you are completely in the ohms law region.
Even if you could put a several thousand volt driver on the motor and run an amp through it no matter what, it's torque wold still drop off. The hysteresis and loss in the magnetic materials used in the motor are the limit here. As the frequency goes up their losses go up as well. All of your added input simply goes to heat. The easy way to look at that is the angle between the voltage and current. You can directly measure what's going on.
In a stepper the torque starts off at the holding torque and pretty much just drops as rpms (or frequency) goes up. Your "dynamic torque" has an upper bound in the static torque. That's what makes static torque a very important parameter on a motor. That's why you can always find it specified.
A motor is a *very* slow thing. Compared to electronics motors simply don't move. Put in a more technical fashion a stepper motor's torque drops off as you try to run it faster. You could get the current up to spec in a nanosecond and the motor would just sit there for a *long* (in nanoseconds) time. You have acceleration and jerk limits on controllers for exactly this reason. You can't take a motor from zero to 10 rpm in zero time. You *slowly* go from static DC to stepping. The only time you ever have high voltage on a stepper is when you are running high RPM's. Except on some very unusual Delta's we just don't run high rpm's.
You can go through the acceleration math and the feed rate math to confirm all of this.
A simple example:
Motor is at rest.
I want to go 10 rpm
I immediately step at 10 rpm
Motor slips
Motor is at rest
I want to go 10 rpm
I slowly accelerate to 10 rpm
Motor does not slip.
In this case "slow" is in electrical terms. I'm accelerating the motor as fast is it can in mechanical terms. On an 200 mm travel at max 200 mm / sec, I spend 1/4 of my time accelerating or slowing down. 250 ms is a *long* time in electrical terms. As the motor starts and finishes it's at low RPM's. Low RPM's mean low drive frequencies. Low drive frequency means that you are completely in the ohms law region.