VFD

I’m still scrounging around, trying to get things ready for the lathe’s arrival. I didn’t want to order a VFD until I knew the lathe was on the way and that all systems were “go,” so I had to do my shopping today.

The issue of VFDs and motor derating is complicated. VFDs are rated in horsepower; this refers to the horsepower of the motors they are intended to drive. For motors over 5 HP with single-phase input–check this yourself, because I may be wrong, and I am almost certainly missing some of the nuances–you have to double the rated horsepower. So for a 5 HP motor, you need a 10 HP VFD. I’m not exactly sure how this works; it may only apply when the VFD is made for three-phase input and you are forced to use single-phase. For smaller motors, there may be no derating at all. I called Hitachi (914-333-2900), and they told me that I didn’t need a giant VFD for a 2 HP motor. I got a 3 HP job; that’s what they recommended.

Had to pay a little extra to get it here on time, but I think that was better than taking a chance on shipping it back and paying a restocking fee. The lathe had not been thoroughly checked out when I ordered it, so there was no guarantee that it would be okay to ship. It would be no fun at all to have a VFD here in a box, with no lathe on the way.

I considered getting a Chinese VFD, and maybe I should have, but this is my first VFD, and everyone says the Hitachis are easier to work with. The instructions are better, and the tech support is very good. I’m going to have enough headaches without having to decipher instructions that still contain literal translations of Mandarin idioms, as well as odd cultural references. “Esteemed customer are to find these VFD having all of Chairman Mao’s Thirteen Industrial Virtues. Death to the Gang of Four.” No, thanks.

I may have screwed myself out of a hundred bucks, but I’m a little fatigued from dealing with tech puzzles. Especially those which commence on Fridays; if you’ve been there, you know what I mean. I’m fairly sure all integrated chips are programmed to fail between Friday afternoon and Sunday night. When you can’t get support. The lathe will probably be here Friday, so I am trying to prepare wisely and avoid being bitten in the rear end by George Santayana.

One great thing about a VFD is that it will stop a machine tool quickly. You don’t have to sit there and wait for the tool to spin down. Bridgeport mills have brakes on them, but not all tools do. It’s my understanding that for heavy braking, you have to get additional resistors or circuit boards, and boy, are they expensive. Luckily for me, the Hitachi folks recommend seeing how the VFD does without the extra stuff, before making the added investment. I think braking would be a great convenience and a nice safety feature. It’s always tempting to grab a moving tool while it takes forever to stop. And a lathe can roll up an operator’s arm like an old sock. You can find photos of this on the web, but I recommend you avoid it.

Pray that Yellow Freight doesn’t mash my prize.