Analog speed controller for Leeson DC motor

Martindag · May 2, 2022

hi guys,

I'm currently working on a project where i need to upgrade the automation of a old machinery.

I currently have 2 DC motor 90v controlled by a Leeson Speedmaster that can be changed manually but i would like to replace that control for something with a analog input to control the speed directly from my omron PLC.

Is there any controller or VFD that can output a single phase 90VDC you can think of ?

(look at the picture for the nameplate of controller and motor).

thanks!

OkiePC · May 2, 2022

Are you needing to keep the manual speed pot as well as have a remote reference? If you can do away with the manual speed knob, you can probably wire a PLC analog voltage output in place of the speed pot, but we'd need to see the guts of that controller to know for sure.

If not, you could replace it with:
https://www.automationdirect.com/ad...high_voltage_(>_50v)/enclosed/gsd5-240-10n4-a

That model provides for a 4 to 20mA analog input. The other versions I looked at that will allow you to use analog voltage input as a speed command were out of stock.

Martindag · May 2, 2022

I like that model, having a manual and auto mode is perfect.
I could do either 4-20mA or 0-10V so its fine.

Thanks for the feedback!

I_Automation · May 3, 2022

Normal DC motor controls with 3 terminals for a pot can have the pot removed and wire a PLC analog output (commonly 0-10 volts, but sometimes 0-5V) to the WIPER and COM/0V terminals.

Some have a feedback output for motor amps draw, and a generator style tachometer on the driven part wired to a PLC input will report the actual speed so you can adjust it as needed.

Martindag · May 3, 2022

ahh i see now, i saw a wiring diagram and yeah that make sense.

bernie_carlton · May 3, 2022

Be sure to note carefully any warnings about directly driving the pot input. The zero pot reference is often not at frame ground but often is halfway between line voltage and line common. At least make your PLC analog output is completely isolated from any other I/O. If you aren't completely sure the drive documentation may recommend a separate isolator.

GaryS · May 3, 2022

Theers guys should have what you are looking for

https://bardac.com/

OkiePC · May 3, 2022

bernie_carlton said:
Be sure to note carefully any warnings about directly driving the pot input. The zero pot reference is often not at frame ground but often is halfway between line voltage and line common. At least make your PLC analog output is completely isolated from any other I/O. If you aren't completely sure the drive documentation may recommend a separate isolator.

+1

If in doubt, use a signal isolator. The first time I smoked a PLC analog output channel was because I used it as a voltage speed reference to a DC drive.

GaryS · May 4, 2022

one option that's still available in a true motor operated POT
you can use your original DC drive add the MOP
then all you need is 2 contact outputs from the plc

Martindag · May 4, 2022

For my job i will most likely replace pretty much everything in my panel, everything is pretty old and hard to find so the 2 speedmaster i had will be replaced.

I will probably go with the IronHorse one with a AI 0-5v to keep the manual pot option available if needed.

Gene Bond · May 6, 2022

Dart Controls and KB Electronics both make DC drives with 4-20 or 0-10 option cards. Most of the brands mentioned here are either one or the other of these 2.

Heed the warning of signal isolation!!!! Most all of the current DC drives in the single phase input range are not isolated power supplies. they are referenced a diode away from either side of the line (sitting in the middle of a full wave bridge from the line).

The isolation modules, or separate isolators often cost almost as much as the drives, but they are required!

Martindag · May 6, 2022

ohh thanks for the warning buddy!

So to prevent any type of ground loops problem, noises and transient signals
a isolator like this one would be recommended?

https://www.levtech.ro/products/galvanic-0-10v-isolator/

Gene Bond · May 6, 2022

Yes, or for example, Dart has an accessory board for most models like: https://www.galco.com/buy/Dart-Controls/-55H(125)

KB has similar....

Analog speed controller for Leeson DC motor

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