Sensorless Vector Control

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VinceS

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Looking for info: Can a inverter duty motor be controlled using sensorless vector control, or is a vector motor required?

The application is low speed high torque chain conv. It will have direct operator control, speed pot, from 0 Hz to 30 Hz or so, maybe more, allowing for inspection of a product as it passes. The motor often is stalled at 0 Hz using the speed pot. The drive is a TB Woods X4 model.

Currently the drive is setup not using the sensorless vector control option, and frequent drive O/L's are occurring as the operator rapidly changes the speed pot and often overcompensates trying to make the chain come up to speed faster.
 
That's an interesting drive choice for your particular application. I use the Wood's drives a lot, since they're made in my town. I've used plenty of Etrac drives, but I'm not sure if I've ever used the X4, however. Don't suppose you called their 800 tech support? They're top notch, speak good english, and will stay on the phone until you're sorted out. Probably just a few settings need tweaked. A change to the ramp time might just do it.
 
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I understand from the Woods website there now made by or maybe just owned by Vacon. I hope this isn't a precursor to another outsourced US product.
No, I haven't yet called the 800 support. I may call tomorrow...

The X4 is the replacement received for the Etrac Drive. I think, shortening the ramp time and possibly using the S curve option might be a fix also..
 
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VinceS said:
I understand from the Woods website there now made by or maybe just owned by Vacon. I hope this isn't a precursor to another outsourced US product.
No, I haven't yet called the 800 support. I may call tomorrow...
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Yeah, I did notice that there's a Vacon sign in front of their electronics shop, now that you mention it. I think they sold off their electronics division, and are focusing on their core foundry business. I can tell you that the electronics shop is still where it always was (for now). I learned a lot about their Ultracon drives by taking them in for repair there, but I don't think they even make DC drives anymore. At least not the Untracon's.
 
VinceS said:
Looking for info: Can a inverter duty motor be controlled using sensorless vector control, or is a vector motor required?

The application is low speed high torque chain conv. It will have direct operator control, speed pot, from 0 Hz to 30 Hz or so, maybe more, allowing for inspection of a product as it passes. The motor often is stalled at 0 Hz using the speed pot. The drive is a TB Woods X4 model.

Currently the drive is setup not using the sensorless vector control option, and frequent drive O/L's are occurring as the operator rapidly changes the speed pot and often overcompensates trying to make the chain come up to speed faster.
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The term "Vector Motor" is just a marketing term used by Baldor. It is just an Inverter Duty motor with a wide speed range (see below) and an integral independent blower attached to it, along with standard options for Encoders.

An "Inverter Duty" (not a true design specification by anybody either) motor is typically referring to a motor designed to be operated at less than full speed and with features necessary to have it survive in the sometimes electrically nasty environments that come with being connected to an inverter. So from that standpoint, if you have a motor that says it is "Inverter Duty", it may be fine. But as I mentioned, there is no universally accepted third-party specification as to what "Inverter Duty" means, so it is sort of up to you to look carefully at your application and the motor specs to make sure it will survive. Vector or non-vector makes no difference in the motor really. BUT...

There are going to be differences from one Inverter Duty motor to another, usually based on the Speed Ratio (or Range) it is rated for. If for instance your motor says it is rated for a 1000:1 Speed Ratio, that means if it is an 1800 RPM motor it can be run at 18 RPM without external cooling. If it says 2000:1, it can go down to 9 RPM. If it says 100:1, it is only good down to 180 RPM though and if it doesn't say anything, I wouldn't trust it. But it should, even if it isn't on the nameplate. You may need to go back to the mfr for specs.

So... because of the fact that people usually use Vector Drives for low speed applications, you could make an assumption that a motor with a 2000:1 speed ratio could be considered better for Vector operation than one rated at 100:1. But if you are operating at 30% speed or higher, it would make little difference; in other words the 100:1 motor would be fine for vector operation.

Back to your application; if you are NOT currently using the Vector mode in the VFD at those speeds, it would be likely that your motor will stall and overload. In V/Hz mode, the best you can typically hope for is a 4:1 speed ratio. So for an 1800 RPM motor, that is down to 250 RPM. When you get slower than that, the motor output torque is unstable and may or may not allow for acceleration without overloading. But if your motor, Inverter Duty or not, is not rated for a high speed ratio, running it at low speeds will not be possible or may require external cooling.
 
Thank you all very much...

Thank you all very much...

I sure appreciate drawing on the knowledge of the group...:smile:
 
Jraef said:
The term "Vector Motor" is just a marketing term used by Baldor. It is just an Inverter Duty motor with a wide speed range (see below) and an integral independent blower attached to it, along with standard options for Encoders.

An "Inverter Duty" (not a true design specification by anybody either) motor is typically referring to a motor designed to be operated at less than full speed and with features necessary to have it survive in the sometimes electrically nasty environments that come with being connected to an inverter. So from that standpoint, if you have a motor that says it is "Inverter Duty", it may be fine. But as I mentioned, there is no universally accepted third-party specification as to what "Inverter Duty" means, so it is sort of up to you to look carefully at your application and the motor specs to make sure it will survive. Vector or non-vector makes no difference in the motor really. BUT...

There are going to be differences from one Inverter Duty motor to another, usually based on the Speed Ratio (or Range) it is rated for. If for instance your motor says it is rated for a 1000:1 Speed Ratio, that means if it is an 1800 RPM motor it can be run at 18 RPM without external cooling. If it says 2000:1, it can go down to 9 RPM. If it says 100:1, it is only good down to 180 RPM though and if it doesn't say anything, I wouldn't trust it. But it should, even if it isn't on the nameplate. You may need to go back to the mfr for specs.

So... because of the fact that people usually use Vector Drives for low speed applications, you could make an assumption that a motor with a 2000:1 speed ratio could be considered better for Vector operation than one rated at 100:1. But if you are operating at 30% speed or higher, it would make little difference; in other words the 100:1 motor would be fine for vector operation.

Back to your application; if you are NOT currently using the Vector mode in the VFD at those speeds, it would be likely that your motor will stall and overload. In V/Hz mode, the best you can typically hope for is a 4:1 speed ratio. So for an 1800 RPM motor, that is down to 250 RPM. When you get slower than that, the motor output torque is unstable and may or may not allow for acceleration without overloading. But if your motor, Inverter Duty or not, is not rated for a high speed ratio, running it at low speeds will not be possible or may require external cooling.
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I think you meant 100:1 and 200:1 ratios.....;)

Since the OP indicated that he intends to use the drive from 0 to 30Hz external cooling seems a must. I wonder if the top limit is 30Hz why not to choose the next higher speed motor, unless of course it is a 3600rpm already.
 
weressl said:
I think you meant 100:1 and 200:1 ratios.....;)

Since the OP indicated that he intends to use the drive from 0 to 30Hz external cooling seems a must. I wonder if the top limit is 30Hz why not to choose the next higher speed motor, unless of course it is a 3600rpm already.
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No, there are motors out there now that are rated for 1000:1 and 2000:1 speed ratios. Some of them are TENV up to 20HP (1000:1), then TEBC above that, but on those, the constant speed blowers are integral to the motor, so you only order one part number.
 
Jraef said:
No, there are motors out there now that are rated for 1000:1 and 2000:1 speed ratios. Some of them are TENV up to 20HP (1000:1), then TEBC above that, but on those, the constant speed blowers are integral to the motor, so you only order one part number.
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1800:18 - the example you used - seem to me 100:1. But maybe you are using 'new' math :D
 
Jraef said:
If for instance your motor says it is rated for a 1000:1 Speed Ratio, that means if it is an 1800 RPM motor it can be run at 18 RPM without external cooling. If it says 2000:1, it can go down to 9 RPM. If it says 100:1, it is only good down to 180 RPM
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I think you've got the idea correct, but a 4 pole on 60 Hz, "1800", would go to 1.8 at 1000:1, or 0.9 at 2000:1, and 18 at 100:1. Methinks you missed your decimal placement.<g>
 
The cause of the problem was...

The cause of the problem was...

again thanks all... I was wondering about the math also but understood the concept so thanks again Jraef. My Marathon motor was rated at 20/1, a bad choice for sensorless vector control.

The operator was using the speed pot to stop the drive. Under a large load the chain would stall with 25Hz still being commanded. This set up a stall condition so the current increased above FLA for over 60 seconds. The drive them faulted with a TOL,( timed overload fault condition ) fault. I need to install a start stop station at the speed pot location to correct the issue. Until then I conducted training for operators to accommodate the bad design.

Has anyone ever used other methods to overcome this problem?
 
VinceS said:
again thanks all... I was wondering about the math also but understood the concept so thanks again Jraef. My Marathon motor was rated at 20/1, a bad choice for sensorless vector control.

The operator was using the speed pot to stop the drive. Under a large load the chain would stall with 25Hz still being commanded. This set up a stall condition so the current increased above FLA for over 60 seconds. The drive them faulted with a TOL,( timed overload fault condition ) fault. I need to install a start stop station at the speed pot location to correct the issue. Until then I conducted training for operators to accommodate the bad design.

Has anyone ever used other methods to overcome this problem?
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Not necessarily a "bad choice". Note that my math was off by a factor of 10 (redface), so at 20:1, you should be good down to 3Hz. But I would still consider an external fan if you already know you are having trouble. If I understood you, the VFD is still NOT in Vector mode, so enabling that and tuning it to the motor should solve your torque issues. If stopping is still an issue after that, you could consider using Dynamic Braking so that any residual kinetic energy in your conveyor is converted to resistor heat. If your VFD does not already have a DB transistor in it, that may be tough to implement though. You never stated the HP size, but typically smaller VFDs have the DB transistor built-in, larger ones need an external module. If it is built-in, all you need to add is a suitable resistor, the VFD manual should explain all that to you.
 
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