[Degrom]

Hi.

I am studying a few steppers motors and was wondering what the characteristics of each motor will be... Both are Nema 23,look the same and has the same weight.

In the left corner we have a motor rated at 6.3V , 3A , 2.1OHM , 9mH...

..and in the right corner a 4.2V , 4.2A , 1.0 OHM , 2.3mh stepper.

If you could tell, what kind of boxers... I mean Stepper will they be?

I am mainly concerned about the first steppers 9mH... Is that good or bad?

All info would be much appreciated.

[Crevice Reamer]

Hi.

I am studying a few steppers motors and was wondering what the characteristics of each motor will be... Both are Nema 23,look the same and has the same weight.

In the left corner we have a motor rated at 6.3V , 3A , 2.1OHM , 9mH...

..and in the right corner a 4.2V , 4.2A , 1.0 OHM , 2.3mh stepper.

If you could tell, what kind of boxers... I mean Stepper will they be?

I am mainly concerned about the first steppers 9mH... Is that good or bad?

All info would be much appreciated.

Hi Degrom.

The first motor will need 96V to perform at its best. That much inductance makes me wonder if it is wired in Bipolar Series. If So, then it will not run very fast before it stalls.

The second motor will run best at 48V. If it has 4 or 8 wires then it is wired in Bipolar Parallel, and that is what we usually want. 4.2A is too high for the 3.5A G540, but this motor would run well with a full sized Gecko.

What drivers will you be using with these motors? What kind of CNC equipment do you want to run with them? How many wires do each of the motors have?

CR.

[Degrom]

The first has 4 wires and the second has 8 wires...

I am planning on using Gecko's and it will be for a CNC plasma cutter.

In what cases will you use the first stepper with the high mH?

Thanks for the info.

[Crevice Reamer]

The first has 4 wires and the second has 8 wires...

I am planning on using Gecko's and it will be for a CNC plasma cutter.

In what cases will you use the first stepper with the high mH?

Thanks for the info.

Okay, so you aren't moving much load, but you DO need axis speed. You will want to run 48V PSU for the 8 wire motor, and that will somewhat undervolt the 4 wire motor.

I'm pretty sure that 9 mH motor is wired Bipolar Series internally. Series motors have most of their torque at very low RPM. I suppose it would work best on the Z because it wouldn't have to move very far at a time and so speed would not be critical as even a fast motor would not have much time to get up to speed.

CR.

[ger21]

You do need to factor torque in here a little bit. It's possible to have two motors with the same inductance with vastly different torque ratings. Or are you saying they both are the same torque?

[yaphiar]

Hi Degrom.

The first motor will need 96V to perform at its best. That much inductance makes me wonder if it is wired in Bipolar Series. If So, then it will not run very fast before it stalls.

The second motor will run best at 48V. If it has 4 or 8 wires then it is wired in Bipolar Parallel, and that is what we usually want. 4.2A is too high for the 3.5A G540, but this motor would run well with a full sized Gecko.

What drivers will you be using with these motors? What kind of CNC equipment do you want to run with them? How many wires do each of the motors have?

CR.

hello
i am new to this stepper motor
do you mean the first motor need 96volt powersupply?where did you get 96 ?
thank you

[James Newton]

This page explains all of it:
techref.massmind.org/techref/io/stepper/estimate.htm

Specifically:

Estimating Drive Voltage

Given a target wattage (which is the power you need from the motor), the voltage needed to drive the motor is that wattage, divided by the rated amperage of the motor.

DriveVolts = Watts / Amps

The voltage on the motor label, is the steady state voltage, or the voltage which the motor can support when it is sitting at rest, which will be much less than the voltage used when the motor is turning. The maximum voltage that the motor can take when turning, the maximum safe drive voltage for the motor, can be estimated from the motors Inductance rating (if known) by finding it's square root and then multiplying that by 32.

MaxVolts ~= SQRT( Inductance in mH ) * 32

In the example above,{ed: see the page for the example, I didn't copy it here} if the 4 amp motor had an inductance rating of 0.75mH or more, then we could feed its driver 24 volts and expect to get about 75 watts power out and drive our 40 lb load at 1000 IPM. That assumes a good lead screw and bearings, and no binding or other loads, of course. It also assumes 100% efficiency, which just doesn't happen, so build in an extra 20% or so as a "reality" factor.

In general, the motor needs more voltage to run at higher speeds, because the voltage pushes the current to the necessary level faster. Think of it like this: If you have a /really/ long garden hose, and you want a trickle of water out the far end, you can supply a trickle at the valve and just wait... eventually, the water will trickle out the other end. But if you want that trickle NOW, you turn the water value on full, then wait for the water to start coming out the end before you turn it down. Of course, if you fail to turn it down, you are going to swamp the motor at the other end of the hose! That is why the motor driver must regulate the current by turning down the drive voltage once the coil reaches it's maximum current flow.

Higher supply voltage allows faster changes to the current and field strength in the motor coils and so faster rotation. But there is also a balance; at higher PSU voltages the motor will get hotter (because of increased wattage) and it will jerk faster from step to step, so you get more resonance and more problems with stalling. A higher voltage can actually stop the motor getting through resonance bands.

Roman Black says: "I hate seeing the "bigger is better" mentality, good design is about balancing all the factors for the exact performance needed."

Also: Java simulation of a stepper motor drive circuit demonstrating the advantage of higher supply voltage combined with current regulation.