Overclock a Baldor VFD 1

[ports394]

I have a VS1PF from Baldor, the 15 hp, 480V, 3phase version.

http://www.baldor.com/support/literature_load.asp?ManNumber=MN763

For a hours of testing, I'm going to be running a 1.5 HP motor from that drive. I've got the settings programmed in to let it run the lower HP motor etc.

But one of our data points I need is at an RPM, that takes me over 60Hz. I've found a few of the Max Freq settings, but it won't let me change them to 70Hz, and the BAS-7 thats at 60Hz, for the motor nameplate, if I turn that to 70Hz, I still can't output 70Hz.

Could someone help me look through this and find the setpoint?

I know that it's possible to burn up the motor during continued usage...and this is not. I'm looking for 65 Hz for 5 minutes.

Thank you.

 

[jraef]

First, to me "over clocking" would refer to forcing the mP to run faster than designed, something that would not apply to a VFD. VFD is actually designed to put out high Hz. Its the MOTOR that may have an issue with it.

I'm not familiar with that specific drive, but in general there are a couple of things to look for.

1) If the VFD is in Vector control mode, that doesn't allow going beyond base motor speed. You would need to put the control mode in V/Hz, sometimes called "scalar" control mode. Check that first, it's most likely. Vector drives now tend to come defaulter to Sensorless Vector Control (SVC) Mode, you would have had to change it in commissioning.

2) Assuming that's not it and you have it in scalar mode, sometimes mfrs tie the maximum speed programming to other parameters, such as the V/Hz pattern or some other issue that provides one final double check against making sure you understand the potential dangers to the motor. Read the manual thoroughly to understand what they might be using to inhibit this.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[dpc]

Jeff,

This may be a stupid question, but why is vector control mode limited to base motor speed and below?

 

[waross]

Thanks for asking DPC. I'm wondering also.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ports394]

jraef, the motor itself can handle it, it's a pretty robust TEFC Baldor.

The scalar control sounds familiar. I'll try to find that in the manual and go from there.

It's just been 3 years since I've tried this, and it was on a different Baldor drive. We had a PC programmer for it.

Thank you.

 

[JG2828]

DPC, Waross,
Jeff alread explained your question in an old post. See Jraef's last post in this thread.

http://www.eng-tips.com/viewthread.cfm?qid=160450

 

[jraef]

Sorry, didn't mean to imply that ALL drives are incapable of over speed in Vector mode, only that this might be a possibility. It has to do with the power of the mP in the drive. SVC requires that the mP maintain a mathematical model of the motor that you either enter manually or it determines by "auto-tune" at setup. Then it has to compare what is sees in the motor current response to step changes against that model and against what you have told it to do in terms of performance (speed regulation, torque regulation etc. etc.). Once you go above base speed, it has to do a lot more number crunching because the motor torque is now diminishing. Cheaper drives don't have the intestinal fortitude to take that on, more expensive ones do, but even then only to a point. Usually there are separate output frequency limits based on the operating mode, i.e. 200Hz for SVC, 400Hz for V/Hz (took that from a Fuji drive spec as an example). If the drive makes no claims to such limits, it usually means they can handle anything you ask it to do, but even then I have been caught by a "gotcha" on that issue when I tried to run a Teco drive in SVC at 75Hz. No can do, but it made no mention of that, I had to hear it from their app engineer.

So I mentioned it as a probable cause in this case because it seems as though the OP is having that same kind of experience I had when that happened to me. I thought I had everything set correctly, and I did, but the drive just wouldn't do it, because as it turned out, it couldn't unless I put it into V/Hz mode.

Now that I've had time to look at the manual link, it appears as though this drive can handle up to 120Hz and makes no restrictions on V/Hz or SVC, so one would imply from that it is capable of it.

So ports394,
How are you giving it a speed command? From what I see, if you are using something other than the keypad or serial comms, you have to program the maximum speed that an external reference will allow, it doesn't seem to be one setting that universally applies regardless of the speed command source. So if for example you set BAS-07 to 70Hz (Maximum Frequency) but you are using an external speed pot or 0-10VDC signal, you have to purposefully set I/O-5 to 70Hz as well to allow the maximum voltage to equal the maximum frequency reference. If you didn't change that, the default is 60Hz. If it's a 4-20ma signal, you use I/O-10 to set the max. frequency for that reference signal.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[ports394]

jraef, I figured I'd have to chain the speed pot settings too. Since I have the VFD mounted on the wall, next to the Speed Pot.. I just but it back into Local so I can use the up and down arrows on the screen to adjust the speed.

Time to hit the book and the VFD. I don't really need the data point anymore, but it's more a matter of principal that I get it working now.

 

[dpc]

Jeff,

Thanks for the explanation - makes sense.

Dave

 

[ozmosis]

ports394
BAS-07 should be the setting for Max frequency.
What about protection for the motor during normal running? even though you will only run for about 5 mins in an overload situation, you should have some protection for the motor in case of unexpected overloads. The protection system in the VFD is unlikly to protect the motor if it is a 10th of the power rating of the VFD. It might be advisable to fit thermistors or similar devices in the motor and connect these into the VFD.