To control motor through PLC

Hi All,

From several days I Trying to get the solution of my problem but i didn't get the solution.
In my Company we have old Adjustable speed motor which control the Mill, in this we are controlling through Potentiometer based speed controller. Mill main motor running in its full rpm (1000rpm/min), by this controller we are controlling the mill RPM.
we have Siemens Step 7 -300 PLC with analog Input and output card.
I need to control this motor through PLC.
Adjustable speed motor description: aux supply 56 Vac, 2.2 A
tachogenerator 2 VA 0-25V (1000r/min)

Current or voltage analog inputs?


So it is currently being controlled by a pot or you wish that in future it will be controlled by a pot?

Currently we are using with POT

And what does the pot control, a VFD?

POT is regulating the voltage of adjustable speed motor, due to this speed regulate

OK, Current or voltage analog input/output modules?

for your reference this is the adjustable speed motor

Current analog input/output modules

https://www.google.com/search?q=wux...UICigB&biw=1034&bih=615#imgrc=u24P1fv9dk84CM:


for your reference this is the adjustable speed motor

sandeepjajawara said:

POT is regulating the voltage of adjustable speed motor, due to this speed regulate

Click to expand...

OK so this is how it works now, currently.


Can you explain how? Do you understand the process and equipment?


In essence, you have the POT now. You want PLC control instead.


Do you mean you want the pot wired into the PLC and a voltage output from the PLC wired to what the pot used to be wired to.


You will need to change the output current signal to a voltage signal, this can be done with a precision resistor.

The link which was shown earlier is our adjustable speed motor.

we have speed controller having potentiometer to controlled the motor speed. for your reference of speed controller please go through this link: http://www.cnwinston.com/Mannufacturer-JD1A-40-Motor-Speed-Control-Regular-DC90V-5A-pd6011224.html

Here we are controlling the speed manually, so I am trying to control through PLC

sandeepjajawara said:

The link which was shown earlier is our adjustable speed motor.

we have speed controller having potentiometer to controlled the motor speed. for your reference of speed controller please go through this link: http://www.cnwinston.com/Mannufacturer-JD1A-40-Motor-Speed-Control-Regular-DC90V-5A-pd6011224.html

Click to expand...

OK. You need to replace this with a VFD that can accept an analog current input signal.

do you really want do it

You have a standard motor that is intended to run at full speed, attached to a variable magnetic clutch that allows you to let the speed slip by varying the strength of the magnetic field of the clutch.

The clutch will have a controller associated with it, and your Pot is probably the analog input to that CONTROLLER. If you want to replace that Pot with an analog output from your PKC, you will need to investigate exactly what that Pot is doing in the control circuit. It may not be compatible with an analog PLC output, but once you know what the speed controller board needs, you can likely get a signal conditioner to go between the PLC analog output and the Controller input (if they are not already compatible).

It sounds as though you are attempting to do something that is beyond your level of expertise, I strongly suggest that you find and employ a qualified automation integrator for this before your attempts cause damage to the likely expensive speed controller module.