[protman16]

Group,

Does anyone have a good source for "low cost" brush DC servo motor? Specs I am looking for are;

Continuous stall Torque - 400 oz/in
Continuous stall current - 10A or less
Max rpm - 5000 or more
Max voltage - 80 VDC

All recommendations appreciated.

Thanks,

Protman16

[protman16]

Group,

I have seen the error in what I was specifying. What I need is a motor that can do the following;

1) Speed of 5000 RPM or more with at least 80oz/in of torque at this speed
2) Continuous torque of at least 400 oz/in at 1000 RPM
3) Voltage needed to reach 5000 RPM must be less than 80VDC

I realise after checking my math that my original post was way off for the current value. It should be about 19A @ 1000 RPM with a 400 oz/in load.

Again any recommendations appreciated.

Thanks,

Protman16

[Al_The_Man]

There are not many DC brushed motors that can attain or rated at 5000rpm+ at that size/torque, look at the Aerotech 1000 series line, these are one that are designed for high rpm.
But even this model has rpm limitations when going up in size.
DC brushless may be a better option.
Al.

[mcpltd]

For this kind of speed, brushless is the way to go.
With brushed at this speed you will have all kinds of problems.
You could get a 3000 RPM motor and over drive it, but only if your duty cycle is not to harsh.
Also 80V is very low for a servo motor of this torque even at 3000 RPM.

[protman16]

mcpltd and Al_The_Man,

I would agree with your posts. After looking for a suitable motor I have decided to do one of the following;

1) Scrape the idea of running brush motors and go to brushless dc or an ac system.

2) Drive the ballscrews directly (1:1) from the motor. This means I need to find a motor that can spin at 2500rpm but I now need 800oz/in @ 500rpm.

Which do you think is the more feasible solution?

[JBV]

A friend recently bought these 850 oz/in servos...

[protman16]

JBV,

In my search for a suitable motor I came across these from a suggestion from another group. They are close but the torque value is a little low for my application. They do look like they would be great servos to match up to a G3X0 drive though.

[mcpltd]

If you are runninig the axis quite fast, and you are supplying the drives near their max voltage, make sure they can handle the bemf or you may pop your driver.

mcpltd and Al_The_Man,

I would agree with your posts. After looking for a suitable motor I have decided to do one of the following;

1) Scrape the idea of running brush motors and go to brushless dc or an ac system.

2) Drive the ballscrews directly (1:1) from the motor. This means I need to find a motor that can spin at 2500rpm but I now need 800oz/in @ 500rpm.

Which do you think is the more feasible solution?

[protman16]

If you are runninig the axis quite fast, and you are supplying the drives near their max voltage, make sure they can handle the bemf or you may pop your driver.

So far these drives have been running at 75Vdc for about 2 years without a single problem. It might be due to the regulated power supply I built... not sure though.

[protman16]

Guys,

Since I have exhausted my search for a suitable DC servo or even a surplus motor that can provide the performance I need, I have decided to switch to a different drive/motor combination. The thing is that there are many different ways to go. I realize that I will have to change power supplies or even go to AC to get what I need. My question is were do I go from here? More importantly which system or method will give me the best bang for my buck?

Thanks,

Protman16

[Al_The_Man]

Probabally BLDC would the most economical, if you are going direct drive to the ball screw get a higher pole count motor than just a 2 pole to give you smoother rotation at low rpm.
You should be able to use the existing power supply if the capacity is there.
I would run the motor sizing through one of the free ones (Kollmorgen etc) to get the correct inertia rating for the motor.
Al.

[mcpltd]

2 pole brushless servo motor? I thought that the minimum would be 4 pole?
Never seen a 2 pole before. (Correct me if i am wrong)
I have only seen 2 pole on a brushed servo.

Probabally BLDC would the most economical, if you are going direct drive to the ball screw get a higher pole count motor than just a 2 pole to give you smoother rotation at low rpm.
You should be able to use the existing power supply if the capacity is there.
I would run the motor sizing through one of the free ones (Kollmorgen etc) to get the correct inertia rating for the motor.
Al.

[Al_The_Man]

Do you mean is it possible or is it common? A 2 pole motor will give you 6 steps/mechanical rotation, (6 steps for every pole-pair).
Maybe not common because of the low speed cogging, Companies like Renco supply Commutation encoders down to 2 pole.
Al.

[mcpltd]

I know it it posible, just never come across a 2 pole brushless motor before.
Didnt think anyone bothered to make them.

Do you mean is it possible or is it common? A 2 pole motor will give you 6 steps/mechanical rotation, (6 steps for every pole-pair).
Maybe not common because of the low speed cogging, Companies like Renco supply Commutation encoders down to 2 pole.
Al.

[protman16]

Probabally BLDC would the most economical, if you are going direct drive to the ball screw get a higher pole count motor than just a 2 pole to give you smoother rotation at low rpm.
You should be able to use the existing power supply if the capacity is there.
I would run the motor sizing through one of the free ones (Kollmorgen etc) to get the correct inertia rating for the motor.
Al.

Went to the Danaher Motion site and downloaded Motioneering Engine software. Ran a few scenarios through Motioneering and came up with a worst case motor requirement of;

Torque = 3.375 Nm
Inertia = 0.0012092 kg-m2
RPM = 5000

Now that I have some specs for the motor and it’s been recommended that brushless DC would provide the best performance to dollar ratio (assuming that I have enough power supply capacity), can anyone recommend a motor and drive manufacturer? I have done some searches on Globalspec and have found a local supplier for the motors, but the cost of about $750 per motor is a little out of my reach. I have looked at Rutex as a possible drive solution. Any others I should know about?

Thanks,

Protman16

[protman16]

Anyone know if these motors (see http://www.cmccontrols.com/mdm-5000_brushless_motor.asp) with Rutex 2030 brushless drives?

Protman16