In need of VFD/Inverter to motor assistance please

[Amelia-BMO]

Hi!

I am currently trying to troubleshoot an Emerson M200 VFD that is running a 2HP motor that gets up to around 200rpm and then overloads and shuts off... so a little background for you.

Motor specs are as follows:
Speed: 1700 rpm
Motor Power: 1.5kW
Horse Power: 2
Motor Voltage: 230V
Rated Current: 6.00A

We will be using this motor along with the VFD to run a stone wheel grinder. We use these grinders to make nut and seed butters at the company I work for; this process consists of breaking down nuts or seeds in a Robo Machine (basically a massive blender) and then slowly adding these broken down products to the grinder until it is full; depending on the consistency of butter you are looking for, it takes various amounts of time to grind these butters. (I apologize if I'm a bit long winded but these details matter in the story, haha). Also note that this is a new motor with a gear box we are trying out to improve the efficiency of butter making, and hopefully removing a few steps in the process that slow us down. The previous motor this VFD was connected to had a few parameter changes and DID NOT have a gear box. We are hoping to achieve a few things with this new motor; being able to add whole seeds or oily nuts (softer and break down easier) directly to the grinder and allowing the grinder to break down the product as well as decrease the run time it takes to make a batch of butter.

I have been on the phone with Emerson numerous times trying to make sure I had the correct parameters on the VFD set according to the motor specs, or if there were any oddball parameters I wouldn't know of changing.
We have rpms, power, frequency, voltage, etc. all lining up between the VFD and the motor, but the motor still overloads and cuts off when it reaches 200RPMs. The guys at the machine shop have shown me that the motor is wired correctly.

Does anyone have any suggestions or experience to help me with this?

 

[anorlunda]

Can you get a thermal image of the motor just after shutdown?

If the hot spot is the bearing instead of the windings or the VFD controller, diagnosis is easier.

 

[russ_watters]

Hi!

Does anyone have any suggestions or experience to help me with this?

Welcome to PF!

My first thought would be too fast of a ramp rate. Typically the VFD is set up with volts proportional to rpm and current follows torque. So too fast of a ramp rate would mean too high of a torque and amperage.

...but that is assuming the torque results from acceleration/inertia. Are you turning on the grinder empty? If it is partially loaded and cold, the high viscosity of the butter would also increase the starting torque.

Have you talked to the grinder manufacturer about this?

 

[Amelia-BMO]

Hi Russ!

I can tell you under the basic parameters that "ramp mode select" is set to standard. I can see that ramp is one of the options under the advanced menu, but I have not worked with that parameter yet. I will check it out.

Yes, the grinder is empty; we just installed the motor, cut it on, and ran into this problem. I don't necessarily have a lot of knowledge on the subject, so this could be a simple fix; something that I am overlooking. This task was given to me by the owner of the company I work for and I am having to learn about these things from the ground up. So I apologize if I'm a bit ignorant on the topic.

I have called the grinder manufacturer but they directed me to the producer of the VFD- Emerson.

 

[Amelia-BMO]

Can you get a thermal image of the motor just after shutdown?

If the hot spot is the bearing instead of the windings or the VFD controller, diagnosis is easier.

Let me see if that is something the guys at the machine shop can do, thank you for the suggestion!

 

[jrmichler]

Here are some more things to try.

If there is an electrician available, ask for a load check. They put a clamp on ammeter on one of the wires to the motor to measure the current. Compare to the torque limit in the VFD. Be aware that torque limits may be expressed as either % of motor continuous torque, or in amps. Set the torque limit to the maximum possible (for troubleshooting purposes). A normal motor can run 300% torque for well over a minute.

Disconnect the motor from the load, and repeat the test.

With the motor disconnected, rotate the motor and grinder by hand and confirm that both of them turn freely.

 

[jrmichler]

So I apologize if I'm a bit ignorant on the topic.

Sounds like you have a plant engineering job. Do NOT ever apologize for not knowing. Plant engineering covers a very wide range of topics, and no one person knows it all. Your ability to do your job is not dependent on your ability to learn everything, but on your ability to find somebody who does. Which is why you came here.

And what @russ_watters says about ramp rate is important if it is a high inertia load. High inertia loads require a slower ramp rate.

I spent ten years doing plant engineering. It was a great job, then I decided to go in a different direction.

 

[jim hardy]

I am currently trying to troubleshoot an Emerson M200 VFD that is running a 2HP motor that gets up to around 200rpm and then overloads and shuts off... so a little background for you.

is that 200 rpm the motor's speed, ie input to the gearbox,
or is it the speed of the stone wheels, ie the motor's speed multiplied by gearbox ratio ?
If the latter, what fraction of full speed is it?

The previous motor this VFD was connected to had a few parameter changes and DID NOT have a gear box.

so the major change was addition of a gearbox?
Did you change the speed of the stone wheels?

old jim

ps - i agree with @jrmichler ,
as a plant engineer you get to see into every designer's "bag of tricks" .

 

[russ_watters]

is that 200 rpm the motor's speed, ie input to the gearbox,
or is it the speed of the stone wheels, ie the motor's speed multiplied by gearbox ratio ?
If the latter, what fraction of full speed is it?

Nameplate speed 1700rpm -- a standard motor. 200rpm, if that's the motor speed, is only 7Hz, which is really slow for a motor like that. My assumption was it was ramping-up and that's as far as it got.

Still, my understanding is this blender was previously set up for an across-the-line start, so I would have thought *any* ramp rate would be fine. So I expect there's a setting wrong on the VFD.

 

[jim hardy]

The previous motor this VFD was connected to had a few parameter changes and DID NOT have a gear box.

First question in troubleshooting: "What changed?"

2HP motor that gets up to around 200rpm and then overloads and shuts off...

Overloads ? Detected how - by overcurrent ?
Was the previous motor also 2hp ?

Still, my understanding is this blender was previously set up for an across-the-line start, so I would have thought *any* ramp rate would be fine. So I expect there's a setting wrong on the VFD.

Same VFD, different motor, different gearing

What else changed ?

old jim

 

[russ_watters]

First question in troubleshooting: "What changed?"Overloads ? Detected how - by overcurrent ?
Was the previous motor also 2hp ? Same VFD, different motor, different gearing

What else changed ?

My read of the OP is they added a VFD to an existing machine and that's it.

 

[jim hardy]

My read of the OP is they added a VFD to an existing machine and that's it.

mine is they replaced (a motor) with a (motor + gearbox)

The previous motor this VFD was connected to had a few parameter changes and DID NOT have a gear box. We are hoping to achieve a few things with this new motor;

a problem well stated is half answered
and this one's not there yet...

the motor still overloads and cuts off when it reaches 200RPMs.

If she's sped up her stone wheels ,
which i assume to be a high inertia load,
it might be as simple as lengthening time delay overcurrent setpoint to outwait the startup .
BUT
I'm naturally apprehensive about what she's done here with the gearbox. Don't want to be party to overspeeding large grinding wheels .

What was hp and rpm of that " previous motor "?
Did she change rpm of the grinding wheels ?
She said she's starting the machine empty , so friction shouldn't be the issue.
That leaves inertia?
Double operating rpm and you quadruple the energy it takes to get there.

What is the rated maximum RPM of those grinding wheels? At what RPM will she spin them ?
Sorry, just my old habits kicking in - safety first.

old jim

 

[Amelia-BMO]

is that 200 rpm the motor's speed, ie input to the gearbox,
or is it the speed of the stone wheels, ie the motor's speed multiplied by gearbox ratio ?
If the latter, what fraction of full speed is it?so the major change was addition of a gearbox?
Did you change the speed of the stone wheels?

old jim

ps - i agree with @jrmichler ,
as a plant engineer you get to see into every designer's "bag of tricks" .

Hi Jim,

200rpm is the speed of the motor. we have a 4:1ratio from the motor to the shaft(this shaft holds a 20 tooth sprocket that is connected to a 100 tooth sprocket under the grinder by a chain), and then another 5:1 ratio from the shaft coming out of the motor to the grinder. So if the motor is running 400rpm, then the grinder (stone wheels sit inside of the drum of the grinder) should be moving 20rpm...

Yes, the biggest change we made was the addition of the gear box. The only changes within the motor (from the motor that this VFD was connected to before the installation of the new motor) was rpm increased ffrom 1745 to 1767 and Amps changed from 6 to 5.4. As far as I can tell, most other motor specs did not change.

Something I noticed yesterday, the vfd is showing that the motor is running at 100rpm before the grinder even begins to turn. This sort of indicated that there is possibly a mechanical problem and not actually an issue with the VFD. Am I safe to assume that.

Funny, I am actually a production manager, and part of my job is running the butter department, I have no experience in this! What I know I have learned in the last two months. So some of these things are a bit hard to comprehend for me.

 

[jim hardy]

Yes, the biggest change we made was the addition of the gear box.

Thank you. I take it you slowed down the grinding stones ?

400rpm, then the grinder (stone wheels sit inside of the drum of the grinder) should be moving 20rpm...

4::1 in the gearbox, 5::1 in the chain drive . So the stones got slowed by a factor of 4?
Having no idea what this looks like i was worried about building a centrifuge .

the new motor) was rpm increased ffrom 1745 to 1767 and Amps changed from 6 to 5.4. As far as I can tell, most other motor specs did not change.

Are those RPM's measured with a tachometer, or just taken from the nameplate ?

just guessing here at something that could match your observations -

1745 rpm is 3% slip ,,, $\frac {1800 - 1745}{1800}$
1767 rpm is 1.8% slip

Going to a lower slip motor means it has less rotor resistance so draws more starting current.
Does it have an entry on the namepate called:"NEMA code" or "code" or "kva code" ? It'll be a letter.
Compare the two kva codes

if you've gone (let's just say) from a code D to a code K motor you've almost doubled your starting current
and that could explain why you trip .
see if your electrician can get a current reading before it trips?

What settings do you have on that VFD to accommodate starting current ?

Something I noticed yesterday, the vfd is showing that the motor is running at 100rpm before the grinder even begins to turn. This sort of indicated that there is possibly a mechanical problem and not actually an issue with the VFD. Am I safe to assume that.

There's an old maintenance man's adage : " ASSUME is an acronym for "makes an ASS of U and ME"
so don't assume, investigate.
Is it just taking up the play in your chain? Or is a sprocket slipping on its shaft ?
You'll learn a lot by firmly grabbing the stone wheel and rocking it back& forth , watching the parts move to see where's any 'slop' in the mechanism.

I have no experience in this! What I know I have learned in the last two months. So some of these things are a bit hard to comprehend for me.

Yes, we learn so much faster by doing than by just reading about doing..
Grab a flashlight and enlist your electrician's help.

above all,
Have fun -

old jim

 

[ChemAir]

A question Emerson should have asked, Is this an inverter-duty motor? In the past I've not had good, reliable VFD operation without the motors being designed for VFD service, with larger problems associated with larger motors.

Also, when the shaft (gearbox output) is changing from 100-200 RPM, what is the frequency doing? i.e. is it changing from 30 Hz to 60 Hz, or is it changing from 10 Hz to 20 Hz (or 5 Hz to 10 Hz). I'm asking this, because some VFD/motor combinations don't like to be run at very low frequencies for extended periods.

 

[Asymptotic]

I am currently trying to troubleshoot an Emerson M200 VFD that is running a 2HP motor that gets up to around 200rpm and then overloads and shuts off

What is the exact error code?
What is the user drive mode (parameter 79)?

Try bringing the speed up slowly to just under 200 RPM where it trips while observing drive-reported speed, voltage, current, torque, and so on (in parameter group 8x). Do any of them become unstable?

If the drive is in a flux vector mode, does behavior change when set to open loop control?

I've seen this sort of behavior occur with drives that have been set up for vector operation (as opposed to scalar, open loop) that were incorrectly autotuned. Autotuning matches the drive to a particular motor, and will calculate a whacked-out motor model if autotuning is performed with physical load connected.