[cstmwrks]

I'm working on replacing a current system ( no longer available ) with my own version. A single stepper is used to pick up a load via a worm gear winch. It takes 134 in oz to pick a full load up.

So I'm looking at motors from AutomationDirect.
This:
STP-MTR-34066

and this:
STP-MTRH-34066

The main difference being 2.8 amps per phase VS 6.3 amps. If I read the specs right the 6.3 amp / phase motor holds its torque rating at a bit higher sps than the one rated at 2.8.


So the motor that I ( currently ) use is set to half stepping mode and runs at 250 sps to a max of 2700 sps. the STP-MTRH-34066 with 6.3 amp / phase should have no issue handling the load. Even the 2.8 amp / phase may be just fine. I could be going overkill on safety factor.

Without debating the motor choice, If your motor is rated at 6.3 amp / phase and the driver like this STP-DRV-4850 is rated to 5 amps.. do you risk damage to the driver, or is the amp limitation on the driver a built in safety factor to the motor as it will only deliver 5 amps per phase?

[H500]

The driver will limit the current.

I recommend the M version with the lower inductance.

[cstmwrks]

The driver will limit the current.

I recommend the M version with the lower inductance.

The MTRH in that model has an inductance of 1.5mh vs 6.6 on the MTR .

Is it common to run motors with a higher amp rating than the driver?

[ger21]

If the driver supplies less current then the motors rating, then the torque is reduced by a proportional amount.

[H500]

The MTRH in that model has an inductance of 1.5mh vs 6.6 on the MTR .

Is it common to run motors with a higher amp rating than the driver?

I mean the H version. Although the low speed torque will be lowered, it will maintain the torque at higher speeds. This is usually far more useful.

[UA_Iron]

The difference between the two is that the MTRH is parallel internal winding and the MTR is in series even though it is not explicitly stated. This is why the 'H' version requires so much more current and is rated to 2250RPM.

You require 134oz-in but at what RPM? What will be your max RPM? 134oz-in with 50% margin is 201oz-in, with 100% torque margin you're looking at ~270oz-in (automationdirect suggests a 100% safety factor margin). The MTRH motor will provide 270oz-in up to about 750RPM @ 70V, while the MTR will see about 375RPM until you're below that safety factor. With the MTR you should be able to run around 50% torque margin though, so you'll squeeze about 600RPM. The reason why they suggest a 100% SF for their motors is that *most* of them are wound in parallel and will generate quite a bit of heat at 100% loading. Since the MTR is presumably not wound in parallel, you should be able to run closer to the torque curve without damaging the motor.

You will want to confirm the above with Automationdirect.

Other questions:
Do you currently have a power supply? What are voltage and current ratings?
Is there a reason why you're going with that driver over the much cheaper STP-DRV-6575 that will supply current up to 7.5A? Are you providing position commands over RS232 (serial) or using the A/B quadrature inputs, or just simply need the functionality that that the STP-DRV-6575 doesn't have?


I have a couple STP-DRV-6575 drivers laying around, along with some of the MTRH-23079 and MTRH-34097 motors laying around and they are excellent products. If you're using serial commands there may be other options that would fit the bill - I'm thinking the Schneider M-drive series integrated steppers.

[cstmwrks]

Other questions:
Do you currently have a power supply? What are voltage and current ratings?

Thanks for the input UA_iron.. No, I have not selected a power supply and am not using anything left over from the old system

Is there a reason why you're going with that driver over the much cheaper STP-DRV-6575 that will supply current up to 7.5A? Are you providing position commands over RS232 (serial) or using the A/B quadrature inputs, or just simply need the functionality that that the STP-DRV-6575 doesn't have?

I have bounced back and forth on the driver based on what is the simplest smoothest way in both ladder logic and hardware to get the job done. Right now this is how thinks work:
I have a stepper with integrated driver that accepts serial commands from a PC. With some pretty simple keyboard commands you can start and stop the motor as well as vary the speed while the motor is moving. Pre set information on speed, torque, direction and so on can be stored and called up by keyboard commands as needed.

Well, if I have some thing that works.. what is the issue? Incompetence of the supplier. Anyhow on the third strike there was no way I would ever deal with that outfit again.

So in my rebuild I don't want to have a PC. I don't see much need for an HMI unless I just want it to look cool. In my most simplest control set up I would have 3 buttons. One for CW, another CCW and a STOP button. Last would be a potentiometer for speed control. Right now I run my motor in half step mode as that is the smoothest. A low of 250 sps and a high of 2500 sps. The pot would be used as needed to vary the speed inside that range.

Currently I'm looking at this motor : STP-MTRH-34097

For what it was worth this driver: STP-DRV-80100 had a 'velocity mode' that accepted input from a pot. I thought it even possible to run with no PLC if all the set up of min/max speed was done with the driver software and just use a 5V signal for step and direction.