maximum rpm of stepper motor

[stevez]

Surplus stepper motors can be purchased inexpensively and often there is limited data available. Is there a way to approximate the RPM that the motor might run at given the information that is usually available such as degrees per step, voltage, current, ohms, etc.? If there's a generally understood maximum pulses per second or some other guideline that's more than sufficient.

 

[Nigel Goodwin]

Surplus stepper motors can be purchased inexpensively and often there is limited data available. Is there a way to approximate the RPM that the motor might run at given the information that is usually available such as degrees per step, voltage, current, ohms, etc.? If there's a generally understood maximum pulses per second or some other guideline that's more than sufficient.

I think the best way is simply to increase the speed until you hit problems, then back off a bit. Bear in mind that the power from a stepper falls off at higher speeds, so you might have to slow it down considerably to get the power you need.

The ones I've got seem to run at about 60 rpm quite happily in half-step mode, fed from a 5V supply.

 

[stevez]

Nigel-if I have no other alternative I'll do just that but I was hoping to have some way to approximate a reasonable limit. Plan is to drive a screw (actually threaded rod) with a nut for linear motion and the rpm might give me some sense of how fast I can expect things to be moving. I was thinking that there was some well known limit to pulse rate. Some reading revealed the recommendation that whatever the final rate, that you ramp up to it and not just apply full pulse rate.

The project-a simple X-Y table that will allow a student to demonstrate skills with controllers and programming. My part is to assist in the mechanical portion in a way that keeps things simple and low cost as the student has a very limited budget. My reward will be the satisfaction that mentors get (can't be described in words) and some one on one tutoring with controllers.

 

[Nigel Goodwin]

The project-a simple X-Y table that will allow a student to demonstrate skills with controllers and programming. My part is to assist in the mechanical portion in a way that keeps things simple and low cost as the student has a very limited budget. My reward will be the satisfaction that mentors get (can't be described in words) and some one on one tutoring with controllers.

There are a LOT! of these projects on the net, usually using PC parallel ports to control them, you may be able to find more info there.

Here's a nice site .[/code]

 

[canadianpoet2012]

stevez,

The thing that will prevent the motor from going any faster, i.e.: reaching its maximum rpm, is back EMF. This is caused by the motor acting as a generator and creating its own voltage. This affectively, cancels out the I/P voltage, preventing it from going any faster.

So, if you are able to find out the number of coils and the number of turns on those coils, that the motor has, with that figure and the current and voltage, you can calculate the back EMF the motor will produce. From there you can work out the speed the motor will be doing at that point, and that should give you your rpm.

Its a bit long winded and the equations to do it, are and can very quickly become more complex, but it is, in theory, possible. It depends if you can find out the number of turns and the size of the coils though, without taking the thing to bits!

Hope this was helpful to you.

 

[falleafd]

Stepping as usual run at 100 to 4000 pulse per second. 4000 pulse seems no load. max RPM depends on your load and your steps.

 

[Klaus]

Stevez, just reading through my stepper motoe application guides, I notice the remark: stepper motors can rotate up to 3000rpm and work well up to 1000rpm.
They recommend using toothed belts & pulleys to increase speeds. Belts also introduce some damping to the output.
They also talk about a natural resonance occuring in the range of 70 - 100 step/second range, which should be avoided as desyncronisation could occur.

I have built a rotating lead screw device for a medical research project, it provided plenty of push torque but the motor screamed if we wanted it to run fast :wink: The programmer had lots of fun in getting the ramp on/off times right for the differend speeds required, its not as easy as it looks.

Klaus

 

[stevez]

Thanks for the replies and information. It sounds like maximum RPM is quite dependent on many things including the motor itself, the power supply, the controller and the load, among other things. It doesn't sound like there is some well known ceiling or obvious limit.

It looks like the student has two choices here-purchase a surplus motor and experiment to see if it can be used or purchase a new motor with known characteristics that meet or exceed the project requirements.

 

[Nigel Goodwin]

It looks like the student has two choices here-purchase a surplus motor and experiment to see if it can be used or purchase a new motor with known characteristics that meet or exceed the project requirements.

I tried looking up stepper motors in the RS Components catalogue, none of them listed a maximum speed - best idea is to rip one out of an old printer or disk drive and have a play with it.

 

[IRQ57]

Stepper motor speed

Stevez,

Just to complete the idea, the speed that a stepper motor can reach is a function of the rise of the magnetic field up to a minimun to overcome inertia and friction to jump from one pole to another.
This rise time depends of the current rise time in the coil and it is a function of its impedance. Impedance is represented as a vector with 2 components: inductance of the coil and resistance.

The inductance of the coil can not be varied, but the total resistance of the circuit can be increased as needed to reduce the circuit impedance by adding an external resistor (speed-up resistor) .

To compensate the resistance losses just increase the supply voltage to get the nominal value in the motor terminals.

In commercial machines is common to find 5 V motors fed with 36 V and a big speed up resistor wasting 6 to 1 power, but with a very fast response.

Regards