Jan 12, 2011

How to Run Variable Frequency Drive In Multi-Speed - VFD Tutorials

All the Drives have the feature of Multi-speed settings i.e we can set up the drive to run at different frequencies according to some input conditions. Here we will see the detailed step by step procedure to run the VFD in Multi-speed. Well every Variable Frequency Drive has some Multi-Function Input Terminals and we can assign these terminals as any function according to our application out of several possible functions like RUN,STOP,REVERSE,JOG,Freq Addition , Multi-speed etc.

How to Run Variable Frequency Drive In Multi-Speed - VFD Tutorials :-
So first of all we need to understand the Hardware Connections required for setting up the VFD for Multi-Speed running . As told earlier that there are some Multi-Function Input Terminals , also there is one Input Common. Here we will take the example of OMRON VFD (BUT settings are almost similar for any VFD only Parameter name changes). IN OMRON VFD there are 5 Multifunction Input Terminals S1 S2 S3 S4 S5 and one input common as SC. By factory default the Multi-Function Input are at Sink Logic , so we will take sink logic at default . We will be using First terminal for RUN Command and other four as Multi-Speed Input Terminals. Make the hardware connections as below :-
If you are using the PLC then from the output of PLC , switch a Relay and short the SC and S1 terminal , if you are using PUSH Button or Selector switch then at one end connect S1 and at other end connect SC i.e whenever the SC will connect with the Multi-Function Input terminal it will be ON . So its very simple , so make the hardware connections accordingly . See the below Picture for better understanding.

After Making the hardware connections we have to set up the parameters in the drive , as we are using 4 input terminals for multi-speed so we will be able to switch between 17 different speeds/frequency as per input conditions.
First of all we will set up the parameters for assigning the Multi-Function input as Multi-Speed terminals Go to Drive parameters and select C-Parameters and make following changes :-
PARAMETER NAME ---------------------------------------PARAMETER VALUE
C001 ----------- Multi-function input 1 selection --------------- O
C002 ----------- Multi-function input 2 selection --------------- 2
C003 ----------- Multi-function input 3 selection --------------- 3
C004 ----------- Multi-function input 4 selection --------------- 4
C005 ----------- Multi-function input 5 selection --------------- 5

Here 0 stands for Forward RUN and 2 , 3, 4 and 5 for multi-step speed setting binary 1 , 2 , 3 and 4 respectively .
Now after setting these parameters we have to assign the respective frequencies for each condition of the Inputs . Let us understand One thing Before , as there are four terminals to which we have assigned Multi-Speed functions , so in other words we can say that we have four binary numbers i.e 0 or 1 , so 2 to the power 4 is 16 So we will have 16 different combination and accordingly 16 different frequency for each input condition.

Parameters for Setting up the Multi-Speed Frequency :-
PARAMETER NAME ---------------------------------------------PARAMETER VALUE
A20 -------------------- Frequency 1 -------------------------------- Set The Value as Desired.
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A35 ------------------- Frequency 16---------------------------------Set The Value as Desired.

Now we are done with complete settings , now you may want to know that which frequency will be when or according to what input combination frequencies will switch , for that see the below table .

Now for example take any condition like 8th condition i.e when multi-function input four will be ON (HIGH) then the VFD will run at frequency specified in Parameter A28.
So we Hope that now you can make the hardware connections and set the parameters accordingly for any number of Multi-Speed Run of VFD , if you just want to run the VFD at 3 or 4 Frequencies then you can just assign this property to two terminals.
If you have any doubts or facing any problem with the VFD Multi-speed settings please drop down a comment an we will be happy to help you out .
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  1. sir ur tutorial is very helpful to me,
    i want some information on vfd,
    here above explanation is good but in coming to design a program part is difficult to me,can u explain using a small ladder program with vfd for allenbraudly
    thank u in advance for ur lot of patience


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