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I have got this LS iG5A VFD to control speed of my rotary cutter machine. I have attached a momentary On/Off switch to start stop the motor and also connected a 10k POT to control its speed

My question is.... I want to program my VFD such that it should start only when the POT is set to Zero and when it starts it should go from 0-10Hz and maintain until i turn the POT and increase the speed.

Please suggest how can it be achieved.


Thank you Raefield

Actually why I am doing this is to prevent the operator from starting the machine on the speed previously set when it was turned off.

Like, the machine was stopped because there was some issue and now after correcting that when we start it instead of going from 0 to 55 where it was previously running the system should stop and when the POT is at zero then start and go from 0 to 10 and wait there so the operator may see that the problem for which the machine was stopped is now over and the operator may increase the speed at his will.

While reading the manual which is not very self explanatory there is an option called Multi Step Speed Functions, is it something which is for my purpose

Thank you once again

Anxiously awaiting reply

Kindest regards Kagazwala

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    \$\begingroup\$ What does the user manual say about this? \$\endgroup\$ – Dave Tweed Oct 1 '18 at 15:42
  • \$\begingroup\$ Nothing as such specifically. It shows how to set the remote start/stop that I have done and shows how to set a remote POT that also is done \$\endgroup\$ – Kagazwala Oct 1 '18 at 15:45
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Having it always start from 0-10Hz with no speed command yet is a simple task, using what most drives call the "minimum speed setting", usually one of the programmable features (you will have to consult your manual for that). Having it not start unless the pot is set to zero is, I think not possible with the standard settings of any VFD that I am aware of. Generally the Start / Stop commands are separate from the Speed commands, and when you hit Start, it starts at whatever the speed command setting is. If using a potentiometer, that means wherever the previous user had left it set. There are a couple of possible variants that I've used however. Whether or not that specific VFD is capable of them is, again, something you would have to determine by reading their manual.

Variant 1. Many VFDs have an option available wherein the VFD is always in a Run state, and you set up the Speed Pot as both the speed control AND the Run / Stop control. How that works is that at some analog value on the pot, let's say 5%, the speed is Zero, meaning stopped. So to "Start" the drive, you move the pot to a value above 5%, and to Stop it, you turn it back down below 5% again. When you do this, you can usually ALSO still have the "Stop" button be functional as a Stop command, but you would not be able to re-start it until you move the pot back to below the threshold again.

Variant 2. Many VFDs have a function called a "MOtorized Potentiometer (often abbreviated MOP) as a speed input option. In that, you increase the speed by closing an assigned input ("UP"), and decrease it by closing another one ("DOWN"). Then you can often "trick" the drive into accepting the UP input as ALSO being the "Start" command, and in conjunction with the aforementioned "minimum speed" setting, you can have the VFD always start when you hit a push button wired to the UP input at that minimum speed, then increase or decrease based on how long you hold the UP or DOWN buttons.

In both cases you must pay close attention in the manual as to how you control the response to a power loss during operation: do you want the VFD to to re-start automatically upon restoration of power, or do you want the user to be forced to re-start it manually? That's a VERY important safety issue.

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  • \$\begingroup\$ Thank you Raefield Actually why I am doing this is to prevent the operator from starting the machine on the speed previously set when it was turned off. Like, the machine was stopped because there was some issue and now after correcting that when we start it instead of going from 0 to 55 where it was previously running the system should stop and when the POT is at zero then start and go from 0 to 10 and wait there so the operator may see that the problem for which the machine was stopped is now over and the operator may increase the speed at his will. \$\endgroup\$ – Kagazwala Oct 2 '18 at 10:16

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