Powerflex 70 speed control

[Dennis g]

Hi all
I have a powerflex 70 that has a remote speed pot and i want to be able to use a preset to speed it up or slow it down by a percentage of the speed pot setting. does this make sense?

 

[Lancie1]

Dennis,

It makes sense that there would be situations where this speed control method would be desirable. The question is whether it can be implemented.

All this raises the question: Why not just raise or lower the remote speed pot setting to the desired level?

Normally, preset speeds must be set inside the drive by programming the parameters while the Powerflex 70 is in program or setup mode. It may be possible to changes these settings remotely if you have a Devicenet or Ethernet connection to the drive. If not, then probably you will be limited to setting each Preset Speed to a defined 0-to-120 Hertz setting (which is not dependent on the remote speed pot setting).

If this drive is connected to a PLC and if you can connect the remote speed pot to the PLC, then you could "simulate" a percentage of the speed pot and send that to the drive using a PLC analog output signal.

Another case could be that you have a series of speeds that the drive needs to run when certain conditions occur. You can set Preset Speeds that change depending on ON/OFF input signals to the drive. But these would have no relationship to the setting of the remote speed pot.

Check your Powerflex manual Parameter List for the Preset Speed set-up. From the Powerflex 70 & 700 Reference Manual, page 2-171, you have 22 choices for the speed reference signal:

The default reference is from the source selected in [Speed Ref A Sel], parameter 90. This parameter can be set to any one of the 22 choices.

It does not appear than any of these 22 choices will do exactly what you described, although some of them might do what you actually NEED.​

 

[Dennis g]

this is on a bottle labeler that runs best with a backlog and is not always fed at same rate so i want them to be able to adjust with pot switch for the product they are running and let 2 photoeyes speed or slow machine

 

[Lancie1]

If you have different speeds for different products, then set up a drive Preset Speed for each product, and install a selector switch that connects to the Powerflex terminal blocks for the Preset Speeds.

From the Reference Manual, page 2-63, the Powerflex 70 can have up to 6 Preset Speeds and two Speed Reference Sources. You can use a BCD Thumbwheel switch to manually change to each of these settings (from binary 000 to 111, decimal 0 to 7).

I suppose it might be possible to use photoswitch inputs to change the Preset Speed settings, or even a combination of inputs from a manual selector AND photoswitches. Many more details would be needed to derive the complete wiring diagram that would perform this function.

If I understand what you are wanting, then the remote pot should set the base speed, and the two photoswitches then modify this speed within some preset percentage of the base speed?

I can see a way to do it if you have a PLC with one spare analog input and one spare analog output. Send the pot setting and the photoswithes to PLC inputs, then write a small logic program that computes the percentage value of the pot setting, then sends this speed setting to the drive using a PLC analog output connected to the drive.

 

[Dennis g]

can i change the accel and decel for the different preset speeds and set them high and the frequency settings below and above range so that the freq changes so slowly it never makes it to the setpoint before the condition changes?

 

[Lancie1]

Let me check the manual to see if each of the Preset Speeds have their own Accel and Decel settings. Based on past experinece, they all use the main Accel and Decel settings.

EDIT: Yes, I think that all the Preset Speeds use the same main Acceleration and Deacceleration time settings. But you could set those so that the frequency does change slowly. You can also set up ramps that are used if certain VFD digital inputs are ON.

There is another option that I just discovered by reading the manual. This drive has a TRIM input selector. The Trim function seems to do what you want: adjusts the main speed input by a preset amount when the TRIM input terminal is ON. (See Manual Page 2-174).

 

[Dennis g]

yeah I couldn't find it in there either was hoping it could be different from start stop accel decel

 

[Lancie1]

Check the TRIM function, page 2-174.

 

[Dennis g]

Great Thanks seems I dont have a complete manual Ill have to download
Thanks again

 

[showshocka]

I am on a similar problem. If I can get a response to this old post. I am working with a Powerflex 700 which is Basically the same setup as the Powerflex 70. Lets say if I use digital-in 2 for "Run" for one speed, how would I use digital-in 3 for another speed? Or could I use the fwd/rev 2 wire control inputs and just make the reverse side a forward in the drive parameters to have 2 speeds from that? Now, logically lets say I wanted to use preset 7 to have a particular speed, would I simply have to supply a digital 1 1 1 somewhere to get that preset 7 to come true? I know this is a Bunch of Questions but I'm right at the point of understanding and not, a lot of years wring VFDs but it's crazy how I've never come across having to wire one for more than one speed, which, by the why will be command by a 3-way selector switch. What will be the most Elementary method to achieve this. I'm also open to tutorials on how to set presets if anybody has any links to provide. Thanks

 

[Lancie1]

Showshocka,

The Preset Speeds must be programmed by setting parameters inside the drive in the program or setup mode. Each Preset Speed (set by you to be a speed anywhere from 0 to Max (usually 60 Hz) is then assigned a binary number than can be entered by sending control voltage to a combination of terminal block numbers on the VFD control Terminal Block. It is not so easy to set up, is not automatic, and requires some study and work to make it happen.

You must know:

(1) Which speed you assigned (programmed by setting drive parameters) to each Preset Speed Number.
(2) What combination of Input Terminal Block Numbers turns on each Preset Speed Number.

 

[DickDV]

Some drives have multiple analog inputs and the ability to do math functions between two or three of them. I don't know if the PF70 has that capability but it seems like what you are looking for. That Trim input should do it too.

 

[showshocka]

I'm well on the right track
http://www.ab.com/support/abdrives/powerflex700/wiring/Selecting_Mutliple_Speed_Command_Sources.pdf

(2) What combination of Input Terminal Block Numbers turns on each Preset Speed Number.

So looking at the picture, is it when the digital input is applied for Preset Speed #4, also send that same digital input to terminal 6? And when the input is applied for Preset Speed #5, send that same digital input to terminal 6 and 4?

 

[Lancie1]

...when the digital input is applied for Preset Speed #4, also send that same digital input to terminal 6?

Well, yes. Basicaly you need 3 inputs (from a PLC or some selector switches or thumbwheel switches or anything else that would generate 3 ON/OFF signals). Connect these 3 inputs to your Powerflex control block terminals 4, 5, and 6. The binary-number equivalent of the ON inputs selects the Preset Speed to be run. For example, if you want to run Preset Speed 6, the Input terminals 6 and 5 both need to be turned ON, while 4 remains OFF. The drive software looks at these terminals, converts the Binary "110" to Deciaml "6", and says, "I need to set my speed setpoint to Preset #6.

Now, logically lets say I wanted to use preset 7 to have a particular speed, would I simply have to supply a digital 1 1 1 somewhere to get that preset 7 to come true?

You keep leaving out the FIRST step: tell the drive WHAT you want each Preset speed to BE. For example, set Preset Speed 6 to "50 Hertz". Only then when you turn terminal blocks 6 and 5 ON, will the drive run at 50 Hertz, and only if it is in RUN mode. You may still need a RUN input, depending on how you set up your drive to operate.

(Preset: something set ahead of the time when it is needed, for example an oven preset to 450 degrees to later bake some biscuits.) The key to making the Preset Speeds work is that you must FIRST set up your Preset Speeds by setting the correct Parameters in your drive's Program mode.

Suggestion: get a copy of the user manual, and learn how to read it, how it is organized, how to find and set the Parameters to make the drive do what you need it to do, then immerse yourself in studying the manual until you find the answers to ALL your questions.

 

[Lancie1]

Study your PowerFlex 70 & 700 Reference Manual, pages 2-68 to 2-70:​

Because any combination of open/closed conditions (or unwired condition) commands a reference source, terminal block seeks ownership of reference selection as soon as any of these input functions are configured, which may happen at power-up. In order for the terminal block to actually gain ownership, the masks must be set up correctly (see above) and no other device can currently have reference ownership. Once the terminal block gains reference ownership, it will retain it until shutdown, until the [Reference Mask] or [Logic Mask] bits for the terminal block are cleared, or until none of the digital inputs are configured as Speed Select input functions.

The Speed Select input function configuration process involves assigning the functionality of the three possible Speed Select input functions to physical digital inputs. The three Speed Select inputs functions are called “Speed Select 1”, “Speed Select 2”, and “Speed Select 3”, and they are assigned to physical inputs using the [Digital In x Sel] parameters. The table below describes the various reference sources that can be selected using all three of the Speed Select input functions.

If any of the three Reference Select input functions are not configured, then the software will still follow the table, but will treat the unconfigured inputs as if they are permanently open.​

In other words, if you do not tell the drive which termianal you want assigned to each Preset Speed #, then it will default to 0 and not run at any speed.​