Hi again! Ive just recieved the contactor i ordered. Its rated for 5kw.. However, i now note that its actually only rated for 1.2kw inductive loads.. Is a spindle /vfd considered an inductive load? Appreciate motors in general are classic inductive loads, but via a vfd? My spindle is rated 1.5 kw. I doubt highly ill ever use it "maxed out". But i dont want risk of anything going "pop" Thanks
Seems unlikely- the energy stored in the coils that it would have to break is buffered by the VFD [/your braking resistor]. There is usually some inductance in an inverter circuit, but even that is gonna be shielded by the full bridge rectifier on the input. I didn't go overboard on my contactor, I don't think it's necessary. I feel like a ton of people don't even use contactors, though after doing the research on VFDs you get the distinct impression they're pretty mandatory, so you're probably still ahead of the game.
I notice "/your braking resistor". Do people generally use one? (yet another purchase i didnt factor in . I had the impression these "small" spindles without lots of inertia are fine without one, as long as you dont set the decleration so some crazy speed.. Mine is currently set at 10 seconds.
Yeah should be fine. Your VFD documentation should have a section on how much of a load it can decelerate using the internal resistor.
Why would that be, I wonder. I got one. It was around $30 shipped from China. After I've installed it I found out it NEVER even gets lukewarm and most likely not really needed. Mind you, my resistor is big enough for a spindle 5 times as big.
So you're not purely relying on your VFD software to make your spindle safe after power events, any floating pins on your control outputs at startup don't accidentally trigger the spindle when you're not expecting it, and so you can control precisely when your VFD turns on in the start-up sequence (to avoid the aforementioned floating pins, etc). It's literally mandatory to industrial codes, but it seems very sensible on an individual basis as well. Generally speaking I don't think it's recommended to loop your e-stop into your relay-contactor module, because the VFD should usually do a better job through its built-in e-stop terminal and make use of the braking resistor to minimize spin-down time. Of course then, you're relying on the quality of your VFD... Which is why I got the Hitachi VFD. And the Schneider-Telemechanique contactor. Doesn't usually pay to skimp, in the long run.
