Advanced VFD controls

[allscott]

Is allscott a tach, encoder, resolver salesman, by any chance? Am mystified otherwise by the comment of always using an encoder. Sure is a lot easier and cheaper to use sensorless vector with a commodity motor rather than an encoder, VFD encoder module, pipe and wire, and a motor built with a backside mounting face.

Of course, there certainly are applications that must use an encoder but, in my world that is less than 1% of the total.

Honestly no I am not but I haven't had the greatest of luck with SVC and my plant is standardized on one brand of drive. I don't have the option of putting in an ABB with DTC, we simply buy one brand of drive and spec all of our OEM machines to come with that brand. Basically if anything we need requires more than V/HZ control we use an encoder.

It would be a different story for sure if we were an OEM and the cost of hardware was a major concern, with us it isn't. Most of the drives we are installing with encoders are replacing older DC units. We are already pulling wire and there is already a pipe from the tach or an existing encoder so running a line for an encoder is never a big deal.

If I could turn back the clock about 15 years and standardized on something like an ABB ACS series drive I'm sure our plant would have a lot of equipment with a lot more sensorless vector control.

I should have qualified my comments a bit before commenting on sensoreless vector.

 

[allscott]

There is nothing radical about operating an inverter-duty motor like a Marathon Black Max or similar from 0 to 100hz. After all, the motor is nameplated to 120hz!

But you do have to understand the motor torque and cooling capabilities over that range and assure that the available torque exceeds the load torque demand at all speeds. In fact, as long as 2% speed error is acceptable and you don't go below 5hz, you wouldn't even need sensorless or flux vector control. Open loop scalar would be good enough if you choose a motor with less than 2% slip.

For tighter speed regulation and/or operation below 5hz, sensorless vector would be needed. That will give you around .5% speed regulation with a good sensorless vector system. If you need better speed regulation or if you need to hold the shaft perfectly still under heavy torque transients at zero speed, then you would need an encoder to close up the speed loop.

These numbers for sensorless vector are very impressive, more than I thought anyone was capable of honestly.

 

[The Plc Kid]

Honestly no I am not but I haven't had the greatest of luck with SVC and my plant is standardized on one brand of drive. I don't have the option of putting in an ABB with DTC, we simply buy one brand of drive and spec all of our OEM machines to come with that brand. Basically if anything we need requires more than V/HZ control we use an encoder.

It would be a different story for sure if we were an OEM and the cost of hardware was a major concern, with us it isn't. Most of the drives we are installing with encoders are replacing older DC units. We are already pulling wire and there is already a pipe from the tach or an existing encoder so running a line for an encoder is never a big deal.

If I could turn back the clock about 15 years and standardized on something like an ABB ACS series drive I'm sure our plant would have a lot of equipment with a lot more sensorless vector control.

I should have qualified my comments a bit before commenting on sensoreless vector.

Allscott what is the brand of your standard VFD now?

 

[allscott]

Allscott what is the brand of your standard VFD now?

Parker, which was for a time SSD and before that Eurotherm.

 

[Tom Jenkins]

Osmanmom had the right idea.

You have to look at a system approach. The performance of the pump, the piping system, the discharge static head requirements, suction head, flow variations, the motor, and the VFD are all related and each part of the system affects all other parts. Looking at any one item, such as the VFD, in isolation will probably lead to wailing and gnashing of teeth in the future.

 

[The Plc Kid]

Parker, which was for a time SSD and before that Eurotherm.

We have some Parker SSD drives in Sensorless Vector setup s and have few issues. I will say that the initial tuning is a little ore involved and a lot of manual tuning to get it right but we have some very challenging drive applications also.

It may be worth a look at the tuning the next time you have an application where sensorless may be a better fit.

 

[allscott]

We have some Parker SSD drives in Sensorless Vector setup s and have few issues. I will say that the initial tuning is a little ore involved and a lot of manual tuning to get it right but we have some very challenging drive applications also.

It may be worth a look at the tuning the next time you have an application where sensorless may be a better fit.

I will do that thanks. The decision (without me) was made years ago that if we were going to go with vector control on an application then we would just go ahead and install an encoder. It sounds like maybe that wasn't the best decision.

 

[The Plc Kid]

Well nothing wrong with having an encoder. I do a lot of over engineering myself but just be aware if you have an encoder fail that you process may not be down and that you may be able to run sensorless and have the same results with the right tuning parameters.

 

[brandoncosta]

Take a look at Hitachi's WJ200 series for a reasonably priced VFD.