Constant Torque vs. Varaible Torque VFD

[Big Daddy]

I set mine up with the SJ 100, when I bought it they (the experts) said this would be big enough. But after I had got it installed and ran it for a while I realized that I might have preferred the bigger SJ200. Because it will easily handle the demands of a heavier load while in ball busting cuts.
You set it up the Hitachi to run your spindle motor “ONLY”! Very important.
Your also going to need some good Schematics to help wire it up. I got mine from EMI, maybe they'll help you out. Lastly,, if everything goes badly for you make sure you have a back-up plain. Namely a good machine tech that can step in and finish if the job if it gets to much. I still have my diagrams, they arent the greatest but I'm willing to lend you a hand anyway I can, just use my private mail box. GOOD LUCK!!!

[Big Daddy]

It doesn't matter you probably already have that set right, my other question is do you have a auto turning feature on your VDF? If so use it and that should solve your problems.

Sorry I posted this on the wrong thread! It suppose to be on the other VDF thread!

[bkamali]

Dear All,
I have an application to replace DC variable speed motor with an AC VFD controlled.
The application is a traightener and Withdrawal in a continious casting machine. I think I need a variable toque system but I am not sure.
Does anybody help me to decide about that.
Thanks in advance.

[perrybd]

The difference between CT and VT are their overloads. A VT drive has an overload of 120% for a minute a CT drive will have a 150% overload for at least a minute.

I'd recommend you take a look at VFDs.com buying guide. It goes over some of the VFD basics you should look into when buying a VFD. Here's a Link to it: Variable Frequency Drive Buying Guide.

Good Luck with your VFD

[mike_Kilroy]

actually the difference is the amount of torque ur motor will provide BELOW BASE SPEED.

ct will give same v/hz line from 0 to base speed so u get nameplae rated torque the whole way.

vt reduces the v/hz curve below base speed along a semi exponential curve so the torque available goes down significantly with lower commanded speed. NOT for a machine tool spindle - for a fan or pump