Aarif

Ramp program for rslogix500

12 posts in this topic

Hi all

I need so assistance with a ramp program on rslogix500. Preferably in ladder logic. I need to control acceleration of a drive using different speeds depending on conditions 

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At its simplest, initialize the setpoint to the starting value and use a self-resetting timer with its preset the ramp step interval. Every time the timer finishes, add the ramp step size to the setpoint until the setpoint reaches the target value.

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The way I implement a ramp is with a timer whose preset is the total ramp time. At any point the output is FinalOutput * (Timer accumulator/Timer preset)

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What you ask may not be as simple as @Joe E. and @b_carlton suggest for the following reasons.

Modern VFD Drives will have an internal Acceleration Parameter.  This ACC Parameter is usually the time it takes to go from Zero to Max but I've also seen it be the time to go from Zero to SetPoint.

If you can clarify some details we can get you a better answer.

I would assume what you're looking to do is have several Setpoints for example 150 FPM , 250 FPM and 400 FPM. 

Each Setpoint will have a different rate at which it goes from Zero Speed to Setpoint Speed?

The Ramp needs to be linear or can it be stepped?

You're using an SLC 500 but what brand of drive?

What communication network do you have between the SLC500 and the drive?

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What SLC/Micrologix do you have? SLC5/03.04 and 05 have a ramp instruction (RMP).

 

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23 hours ago, b_carlton said:

The way I implement a ramp is with a timer whose preset is the total ramp time. At any point the output is FinalOutput * (Timer accumulator/Timer preset)

Yea I was hoping to find a easier solution. With less logic. But if I have to then I will use this method. Thanks

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22 hours ago, Mickey said:

What SLC/Micrologix do you have? SLC5/03.04 and 05 have a ramp instruction (RMP).

 

I'm using 504. Where can I find this instruction? I've looked

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23 hours ago, BobLfoot said:

What you ask may not be as simple as @Joe E. and @b_carlton suggest for the following reasons.

Modern VFD Drives will have an internal Acceleration Parameter.  This ACC Parameter is usually the time it takes to go from Zero to Max but I've also seen it be the time to go from Zero to SetPoint.

If you can clarify some details we can get you a better answer.

I would assume what you're looking to do is have several Setpoints for example 150 FPM , 250 FPM and 400 FPM. 

Each Setpoint will have a different rate at which it goes from Zero Speed to Setpoint Speed?

The Ramp needs to be linear or can it be stepped?

You're using an SLC 500 but what brand of drive?

What communication network do you have between the SLC500 and the drive?

Ok I'm using slc 504 controller. I've got an analog out module -10v - +10v. I'm using a parker dc integrator 590+ series 2 drive. 

My problem is... In reverse I need 1sec acceleration... but in forward i need to ramp the drive to setpoint. Preferably over 10secs. I'm using MOV blocks to achieve different setpoints. I can use a timer and use the acc of the timer to ramp. But this requires alot of logic.

Edited by Aarif
I can use a step to ramp the drive. Doesn't have to be linear

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44 minutes ago, Mickey said:

Thank you. So I can just move that interger to my analog out for the drive. Will give it a try in the morning. 

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@VFD Guy has asked a pretty valid question, which @BobLfoot eluded to; different drives treat accel ramp rate differently. If accel is set to ten seconds, some drives will take ten seconds for all speed changes, from current speed to new setpoint, while others assume a zero to setpoint, and scale the difference if the drive is already running. 

Let us know how the RMP instruction works out for you.

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