Motor Speed surprise at the end of project. New product requires 3 Hz ( 12 RPM )

Good Afternoon ,

I had posted earlier with questions concerning Inverter Duty motors , but yesterday I received a surprise that we are getting another product on this machine I am upgrading , that is going to make these motors run at 3 HZ , to run this machine at 12 RPM's . I am using Baldor Washdown Inverter Duty Motors ( 5 HP ) with no fan. I ran these motors for a little over an hour , and did not see any obvious issues. I know this is not normal. Do you guys think I will have any serious issues with these motors running at 3 HZ ? This is a surprise at the end of this project. With all the products running on this machine , they all ran between 40 HZ to 56 HZ , now this. I don't have enough in the project budget to make major changes . Do you guys think I can get away with this ?

Thanks so much for your help.

What about using a gearbox?

That is a question for Baldor, although I am still waiting 1 week later for an answer to a basic motor question(max mechanical speed). I know of some "inverter duty" motors that are not rated for full continuous torque at less than 20Hz.

3Hz on a 60Hz motor is called a 20:1 turn-down ratio. Baldor should be able to tell you their rated turn-down capability based on the model of motor you have. 20:1 is kind of mid range for inverter duty, better ones are 40:1 in TENV, which is that you likely have, 10:1 is typical for low-end motors that still say inverter duty. But as I mentioned in your other thread, Baldor has been playing a little fast and loose with terminology of late. So it's going to take a phone call.

Does this Motor description tell you anything ?

Thanks for you help,

IDWNM3707T
Baldor Motor, 5HP, 1760RPM, 213TC TENV
Inverter Duty Washdown Motor, 1000:1 CT
Rated, W/ Thermostats and Encoder Mounting
Provisions

You are using a Flux Vector drive that uses an encoder feedback
I don't see the problem just set the speed down to 3 hz
I di it all the time I have run them down to 0.2 hz and lower without a problem
just use a vector duty motor that's rated for continues duty
actually on a system I just completed I saw the output frequency at 0.02 hz while it went in position.
actually they can run a 0.0 hz position hold or sometimes called zero servo

I'm not using an encoder. I did Auto Tune the drives with their motors.

with out an encoder the best you can expect is about 5 - 6 hz without cogging
put an encoder on save yourself all the aggravation

What do you mean " Cogging" ? On the PowerFlex 525 it looks like you need to add an encoder module. What parameters would you modify to accept an encoder ? What is the biggest issue facing a motor and drive at lower frequency ? What benefits does an encoder give at much lowere speeds ?

Thanks in advance,

Cogging is when the motor out shaft acts like its rolling over a gear.
Very unstable operation
I don't know the parameters for a Powerflex drive my standard is Yaskawa
in this case I would use an A1000
I have run welding beads at speed as low as 0.5 hz you can run them at 0 and hold the load. but encoder is necessary

That motor is good for 1000:1 speed ratio, so basically it can almost stand still. If you are using a PF525 in SVC mode and did an auto tune, you should be fine.

Good . I feel better. Thanks so much for all your help.

A good sensorless vector drive on that motor will give you good service at near zero speed. The key is to turn up the motor loop good and tight. That business of less than 5-6 hz not possible without an encoder is nonsense. Just use a good sensorless vector drive (AB, ABB, Mitsi, Yaskawa) and you'll do just fine. And that motor can cool itself at essentially zero speed.