VFD / Motor experts, O.L. Faults on Yaskawa V1000

milmat1

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I have an application where I have a 5HP TEFC Baldor running open loop from a Yaskawa V1000 drive.
At times due to environmental changes the motor slows to as low as 14Hz trying to maintain the proper flow of material. Well at these speeds it trips with an OL1 Fault. At this speed there is not enough HP to drive that belt and it will sometimes stall the motor before it trips..

My report stated that we simply have to change the gear ratio and get the motor into a higher rpm, or we need considerably more HP.

Mechanical guys suggest putting a Baldor TEBC Inverter duty Vector motor on this application. 1000:1 constant torque speed range, Of the same HP....

What if anything, is that going to accomplish? I mean Power is Power and Current is Current. I have a 5HP Drive topping out on current, the 5HP motor is demanding more than the nameplate FLA under these circumstances. Is a TEBC motor going to make any difference ?
 
You say it is running "open loop", what do you mean by that? Open Loop Vector Control (A1-02 = 2), or V/f control (A1-02 = 0)? The reason is, if you mean V/f control, the lack of torque accuracy starts to hit you at slow speeds like that, that's where you need Vector Control, and "open Loop" vector control is usually fine. That provides you with more torque PU of current at slow speeds, which is usually where you need it.

If you are already using Open Loop Vector control, then if your motor is drawing more current than it is rated for, no amount of cooling is going to change that.

But also, what is your setting of L1-01? That can make a difference. If left at the factory default (=1), you will get an OL1 warning at 90% of the torque capacity of the drive after about 5 seconds, trip at 100% in 60 seconds. If you get a motor designed for use on VFDs (10:1 speed ratio) you would set it for (2) and run at 100% torque continuously. So that may be why they are recommending the better motor, it will allow you to tweak that. If however your motor is pulling more than 100% FLA continuously, it will still trip.
 
jraef has some great points.

I will attest to the baldor motors. I've used a TENV motor with similar characteristics that has constant torque down to 0 Hz.
the one I used was: http://www.baldor.com/catalog/IDWNM3707T
Now, I still don't understand based on my electromagnetics classes how they can provide constant torque with an AC motor like that, but I'll tell you it works. We used that motor with a rockwell 525 drive in open loop vector, and it ran at <3Hz for extended periods with no problem.
 
I started out if V/F control in my original setup. When we started having this issue I worked with Yaskawa and we tried both. And he (Yaskawa tech) Ran me through several different sets of parameter for the motor parameters. To be honest I would have to pull the modified constant's to tell you where we ended up at. At the end of the session even he agreed that we may just not have enough HP to operate at these super slow speeds..
 
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jraef has some great points.

I will attest to the baldor motors. I've used a TENV motor with similar characteristics that has constant torque down to 0 Hz.
the one I used was: http://www.baldor.com/catalog/IDWNM3707T
Now, I still don't understand based on my electromagnetics classes how they can provide constant torque with an AC motor like that, but I'll tell you it works. We used that motor with a rockwell 525 drive in open loop vector, and it ran at <3Hz for extended periods with no problem.

That is impressive. My understanding is stretched on this myself. I mean I understand power and I understand HP is a function of velocity and force. (RPM - Torque). So to maintain the torque without the RPM's seems like it would require a lot of current.....Hence my problem...
 
yep, those charts don't lie. If you can't tune your existing motor to work, then I'd suggest trying that. I ran the autotune and it worked out of the box.

good luck.
 
That is impressive. My understanding is stretched on this myself. I mean I understand power and I understand HP is a function of velocity and force. (RPM - Torque). So to maintain the torque without the RPM's seems like it would require a lot of current.....Hence my problem...
Torque and current are essentially synonymous when using a VFD, so the current would NOT change. The motor creates torque via magnetic flux, and flux strength is related to the ratio of voltage and frequency that the motor was designed around. The trick that a VFD does is to maintain that same V/Hz ratio so as the Hz changes, so does the voltage.

The reader's digest version of Vector control is that inside of that motor, SOME of the current goes toward establishing the flux in the first place, i.e. magnetizing the core (Flux Current), and the rest goes toward increasing the flux strength to produce torque (Torque Current), and they take place at different points in the AC sine wave; flux then torque, flux then torque, flux then torque, repeat every cycle. The flux current requirement remains relatively constant as a percentage of applied voltage, which in a VFD, is changing with speed. The torque current varies with load on the motor causing an increase in slip. In a standard V/Hz drive everything changes together, as you lower speed, some of the flux current as a percentage of total current is unnecessary and gets wasted as heat. A Vector Drive can separate the vectors of flux current and torque current so that the motor is only given exactly as much flux current it needs at the relative voltage, leaving more of that current available for torque production. To do so, it needs to KNOW that angular position of the rotor in the magnetic fields. Closed Loop vector does that with an encoder feedback, "Open Loop" vector is not really open loop, but the sensors that tell the drive where the rotor is are built in to the drive. Open Loop is not as accurate, but it's good enough for 99% of applications.
 
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I have an application where I have a 5HP TEFC Baldor running open loop from a Yaskawa V1000 drive.
At times due to environmental changes the motor slows to as low as 14Hz trying to maintain the proper flow of material. Well at these speeds it trips with an OL1 Fault. At this speed there is not enough HP to drive that belt and it will sometimes stall the motor before it trips..

My report stated that we simply have to change the gear ratio and get the motor into a higher rpm, or we need considerably more HP.

Mechanical guys suggest putting a Baldor TEBC Inverter duty Vector motor on this application. 1000:1 constant torque speed range, Of the same HP....

What if anything, is that going to accomplish? I mean Power is Power and Current is Current. I have a 5HP Drive topping out on current, the 5HP motor is demanding more than the nameplate FLA under these circumstances. Is a TEBC motor going to make any difference ?

You are not running out of power. You are running out of torque. As others have pointed out, that means you are running out of current capacity in the VFD. A conveyor is essentially a constant torque load, and the VFD must be selected accordingly.

Using a higher numerical gear ratio increases torque output, which is proportional to gear ratio. The trade off is lower speed at 60 Hz. You would be able to use the same hp since hp = torque(ft lb) x rpm / 5252. Higher torque, lower speed, same hp.

It might be less expensive to replace the VFD and/or motor. Check the torque on the existing and new motor and the amp rating on the new VFD. If the existing motor has enough torque then only the VFD needs replacement. If the VFD has enough current capability only the motor would need replacement.

Designers should always determine if the load is variable torque or constant torque in component selection.

Using a totally enclosed blower cooled motor probably won't solve the problem. That design is intended to eliminate motor overheating at low speeds. It won't change the motor torque demand or current draw.
 
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You might be able to swap that 1800rpm motor for a 1200rpm motor and gain considerable torque... depending on mounting, you may not be able to fit the 1200rpm motor's frame, but worth a look.
 
You might be able to swap that 1800rpm motor for a 1200rpm motor and gain considerable torque... depending on mounting, you may not be able to fit the 1200rpm motor's frame, but worth a look.
That's not a bad idea, considering that you are wanting to run it slower anyway.
(y)

The caveat would be at the other end; if you wanted to run at the previous full speed (1750RPM). You could over speed the motor with the VD, but would lose torque at that end (once you get above the 1200RPM motor design speed). Still, might be OK.
 
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Similar to jraef's point in post #2, does the drive have a derating curve for use with TEFC motors operating below a certain speed? I have never used a Yaskawa drive so I don't know. But it would be significantly more aggressive that the 90% derating that jraef referred to if it was there. For example, with an AB Powerflex 750 series drive the max continuous overload current at standstill for a TEFC motor used by the motor heating model is (I believe) 60% of motor nameplate and doesn't rise to full motor nameplate current until 20 Hz or above.

This also plays into what an "OL1" is. Are they referring to a motor heat model overload or a continuous current overload. As stated above, those could be two different things.

Finally, what kind of a load is this. To match the statement that the motor current is climbing above nameplate at low speeds the load would need to be increasing as speed decreases. While these load types do exist they aren't ac common as constant torque (conveyor type loads) or "variable" torque (centrifugal pumps and fans) loads.

Keith
 
...The caveat would be at the other end; if you wanted to run at the previous full speed (1750RPM). You could over speed the motor with the VD, but would lose torque at that end (once you get above the 1200RPM motor design speed). Still, might be OK.

Yes, the torque available at 1800 rpm (90hz) would be right back where you were with the 1800rpm motor (@60hz). Still just 5hp.
 
Torque and current are essentially synonymous when using a VFD, so the current would NOT change. The motor creates torque via magnetic flux, and flux strength is related to the ratio of voltage and frequency that the motor was designed around. The trick that a VFD does is to maintain that same V/Hz ratio so as the Hz changes, so does the voltage.

The reader's digest version of Vector control is that inside of that motor, SOME of the current goes toward establishing the flux in the first place, i.e. magnetizing the core (Flux Current), and the rest goes toward increasing the flux strength to produce torque (Torque Current), and they take place at different points in the AC sine wave; flux then torque, flux then torque, flux then torque, repeat every cycle. The flux current requirement remains relatively constant as a percentage of applied voltage, which in a VFD, is changing with speed. The torque current varies with load on the motor causing an increase in slip. In a standard V/Hz drive everything changes together, as you lower speed, some of the flux current as a percentage of total current is unnecessary and gets wasted as heat. A Vector Drive can separate the vectors of flux current and torque current so that the motor is only given exactly as much flux current it needs at the relative voltage, leaving more of that current available for torque production. To do so, it needs to KNOW that angular position of the rotor in the magnetic fields. Closed Loop vector does that with an encoder feedback, "Open Loop" vector is not really open loop, but the sensors that tell the drive where the rotor is are built in to the drive. Open Loop is not as accurate, but it's good enough for 99% of applications.

That is an excellent explanation !!
Thank You !!
 
You are not running out of power. You are running out of torque. As others have pointed out, that means you are running out of current capacity in the VFD. A conveyor is essentially a constant torque load, and the VFD must be selected accordingly.

Using a higher numerical gear ratio increases torque output, which is proportional to gear ratio. The trade off is lower speed at 60 Hz. You would be able to use the same hp since hp = torque(ft lb) x rpm / 5252. Higher torque, lower speed, same hp.

It might be less expensive to replace the VFD and/or motor. Check the torque on the existing and new motor and the amp rating on the new VFD. If the existing motor has enough torque then only the VFD needs replacement. If the VFD has enough current capability only the motor would need replacement.

Designers should always determine if the load is variable torque or constant torque in component selection.

Using a totally enclosed blower cooled motor probably won't solve the problem. That design is intended to eliminate motor overheating at low speeds. It won't change the motor torque demand or current draw.

which gets back to my original statement, which I was hoping to verify. We simply haven't got enough HP to begin with.
Yes we could change the gearbox and get the motor in a happier spot on the RPM scale, but at the cost of reducing the top speed.
The big man upstairs (The Owner) Want to put a vector drive Baldor on this thing. Because it claims 100% Torque down to 0Hz.
I cannot understand how it does this though, Without using more current......
 

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