CNC Newbie needs advice and Guidance

Hey Espressomatic,

look, Espressomatic, neither you follow the references I always provide, nor you are attentive. Here we were talking of VFDs for single-phase input. That is exactly what is available as domestic electricity in North America (as you correctly state) since you have split-phase electricity in domestic areas.

You forcibly need a VFD to run a spindle, because a spindle is a three-phase asynchronous induction motor (called “spindle” here) and such a motor forcibly needs three-phase electricity. And a VFD is a device that creates three-phase electricity. That’s what it does.

You didn’t forget that when a spindle is rated with 10 A and a VFD with 10 A output, that a VFD produces three phases at the same time? So when you draw these currents from one single phase supply circuit, what do you think to what that the input current then forcibly arises?

This is physics, not magic. If you want to know, the formula for the three-phase motor is here and you still will have to add the efficiency of the VFD itself. But I am sure that people like you are not interested in these facts, and that you won’t even look.

Look, you’re just embarrassing yourself here with your alternative facts instead of reading up on the facts I always reference, which are available for everyone to read and verify. You better stop before you embarrass yourself even more.

Precisely. The VFD mentioned above is rated 24 A input current (and the fuse recommended as per the VFD manual 30 A for this reason, as you need a few percent reserve) because it is made for the case that at any time, you attach a spindle that is rated 12 A on three phases to it.

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