How should I wire a 2/4 pole 2-speed motor?

J

joe_m

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I bought a motor I thought was a simple, new, 3-phase, 1700rpm motor for my mill. When I finally convinced the guy to mail it I got what looks like a 2-speed, 2 or 4 pole motor with this baseplate:
newmotor.jpg

It's going on my mill to replace the single-phase 1.5hp 1750 rpm motor currently there. I just ordered another VFD so I've got at least until Thursday/Friday before I can wire it up.

I'll be bypassing the on/off and reverse switches currently on the mill and just using the on/off switch on the VFD to power it. I do have a 5-step pulley to provide variable speed and I know I can turn the knob on the VFD to increase/decrease it a bit. My lathe runs off a VFD though, and I find myself switching speeds via the gear levers, never via the VFD knob.

So should I wire it at 1700 or 3400? I know carbide likes higher speeds, but all my tooling is HSS. I work mainly in simple steel, occasionally in brass, next to never in aluminum. I've read a half-dozen other threads in other forums on these motors and some of them say that if I wire it at 1700 I'll get the slower speed, but also less torque. I don't want to wire it for 1700 and find out I've just converted a 2hp motor into a 3/4hp motor, but I don't want to wire it for 3500 and find I have to dial it down to next to zero at the VFD because otherwise it's too fast.

thanks
Joe

newmotor.jpg
 
If the speed range on your mill is adequate now, I would wire it for 1700RPM.
 
Well it's done, except it's on the high speed and I need to go back out and move the wires. Thanks KennyD for the suggestion.

I didn't even read the instructions for the VFD because it was the same model as the one for my lathe, and I thought it would be easy since I've already wired up thelathe, but I screwed up big time - a very boneheaded mistake. If you look at the diagram in the pic, I saw that word "Connect" but didn't look closely. So I spent a long time jumping U1-U2, V1-V2, W1-W1. It wasn't easy because they were so close to each other and the wire was too fat to bend easy. But I got it done. The VFD arrived today and I hooked it up and turned it on and all it did was make the motor screech and I got about 1 RPM. That wasn't the real mistake. The real mistake was that after the VFD kicked off I tried it again. And again. And just for grins, I tried it again. Then I finally figured out that there was a problem - probably a serious case of operator locked in anal-cranial loopback so I unplugged and looked at the pic again and realized that it wasn't telling me to jump anything. So I took off the jumpers and tried again and it sounds sweet - 1/10th the noise that the old contraption made. But of course I had misread the diagram again and thought I wanted everything on terminals #1 for 1700 rpm. I need #2, so when I go back out I'll switch them over and that will slow it down to where I want.

Joe
 
Joe, sometimes we are simply forced into doing the correct thing.

Not that I would know from personal experience...

Bill
 
At least you didn't let the magic smoke out of the VFD:lmao:
 
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