Soft Start vs VFD for 5hp motor

[rockman7892]

I am trying to decide weather or not to use a soft start or a VFD for a tripper car dirve motor which is 5hp at 480V. Right now we are just using a full voltage reversing starter (FVR) and when the tripper car gets to one end of the track the forward starter drops out, it pauses briefly (couple of sec) then the reversing starter pulls in to send the car the other way. It does the exact opposite at the other end of the belt.

To aovid wear and tear and the constant hammering of the starter and tripper car itself when the starter pulls in, we want to add a soft start or VFD to allow a smoother transition and startup when reversing direction. I'm not sure which one will work best for this application or which one is more economical.

I dont believe that we'd be varying the speed of the drive at all once it is up to full speed, so that why I'm not sure if a VFD would be worth it in this case. In other words we are just looking to ease the drive slowly up to speed then let it run at a certain speed to the end of the track and either ramp the speed back down or just let it come to a stop at the end of the track.

Has anyone had experience or know what will work best for this type of application?

 

[rockman7892]

"So what happens at design time is that the Engineer determines the WK2 (inertia) of the load, the starting duty, speed and the required torque at the shaft, then (hopefully) refers to those NEMA guidelines to pick out the proper motor."

Jaref

Do you have a copy of these NEMA guidelines used for selecting a motor based on the above variables. Do you have the guideline for the duty cycles avaliable?

Thanks

 

[jraef]

Do you have a copy of these NEMA guidelines used for selecting a motor based on the above variables. Do you have the guideline for the duty cycles avaliable?

I can't publish the file itself because it is copyrighted material, but this chart is readily available all over the net.

 

[jraef]

Oh and if you are interested in obtaining the complete specification, it's in NEMA MG-10, not MG-1