Created Date: January 04,2014

Created by: bcarlton

Many VFDs provide a few methods to control the speed externally

By following an analog input

By presetting speeds then selecting from them by digital inputs

By commands using a communication channel

If you provide the exact model number of the VFD we may be able to providee more help. In the meantime just read any documentation you cann find concerning the VFD.

Created Date: January 04,2014

Created by: mudger

First thing you need is and analog out module, determine the type by finding what’s compatible with your VFD analog in. Set up your module in ladder logic (I-Box is a simple way to do that). The output data address is where you have to put the value that will be used by the module to generate what value is going to the VFD. If you are using a current module 4-20ma with 16 bit resolution or 1-10v 16 bit resolution the value will be between 0-65535.

The output address will be a V memory address and let’s use V2000 for example.

Now all you need is a means to set V2000 to the desired value for the speed you want. Full speed 65535, half speed 32768 etc.

You can use a PID set point set through some compatible HMI or use the HMI to set speed by operator input, if you need Variable speed. There are other ways to manipulate the value in V2000 but this is simple and common.

If you only need a few preset speeds you don’t need a plc at all. Just use push buttons or selectors and configure the presets on your VFD.

The HMI value will need to be loaded into a V memory location and then scaled and sent to V2000.

V2000 is the beginning address for the module double words for all module outs and are in BCD format.

V2000 is channel 1, V2002 is channel 2 etc.

Hope this gets you started.

Created Date: January 06,2014

Created by: leochimy

thanks i now have a rough idea of what i have to do.basically my project involves automation of a mine rock winder.it is basically an elevator that carries rock out of a mine shaft. The motor that determines the winder motion has to follow the following sequence for the up trip:

after loading has completed the winder moves at a slow creep speed (20% of full speed) for about 3seconds to steer clear of the loading area,

it accelerates to full speed and mantains that speed for a preset distance until it it reaches a limit switch that initiates deceleration to 20%of full speed

then a limit switch initiates it to stop signalling the end of the cycle

the motor that i am looking to control is a 200hp squirrel cage induction motor which is supplied with 550v.