question for variable frequency drive (VFD) people

C&P 8x12 with a 1/2 HP 40 amp 3 phase motor with a 3” pulley wired to a GE Fuji VFD. I a running a v-belt

Everything wired up well and is operating. I still had my base and plate locked up from a blind deboss run a week ago. I ran that run first and was very cozy with the speed. I was getting about 15-20 per minute (whilst I was teaching a beginner). I actually wanted slower but it seems the motor does not agree with lower speeds and gradually slows down and motor struggles until I push the flywheel a bit for it to catch up.

That aside, We went to our second pass which had ink. I put on the rollers and inked it up. Everything changed completely!!! Something is dragging the press considerably.

The press is totally oiled well. So my questions are…

-Is there not enough amperage for the motor to pull that weight? (is 40 amp)

-Is it a problem with amperage from the wall?

-Is the pulley to big? My gut is telling me that a 2” pulley may help. But not drastically in my mind.

I dunno a 1/2 hp motor should be plenty.

- Or finally is my motor not so good overall?

Anyone’s thoughts please.

Log in to reply   4 replies so far

Isolate, identify and eliminate potential problems one at a time. Unbelt motor from press. Without chase in press, turn flywheel slowly by hand. If you have the rollers in, it should get a bit harder when the rollers go over the shoulders of the rails. All other parts of the cycle should turn freely without binding. Turn the flywheel away toward the back of the press. With hand on spoke at about 11 o’clock, give the flywheel a strong full 1 1/2 turn pull and pull up strong and let go. The press should turn several cycles. If all is well here, look to the electrical end. A correctly running 40 amp 1/2 HP motor is plenty.

Make sure you’re oiling the left and right flywheel journals (where the shaft of the flywheel passes through both sides of the press). These are often overlooked and can cause some pretty serious friction if neglected.

It sounds like when you were debossing you weren’t using rollers. Adding the rollers and ink to the press will add a significant amount of drag/resistance. You’ll have to speed up the motor to overcome this added resistance.

Your motor amperage shouldn’t matter too much. The horsepower and RPM will be the more important factors. That being said, your 1/2hp motor shouldn’t be the issue. However the torque of the motor will decrease as the speed is lowered by the VFD.

With a 2” pulley you’d be able to speed up the motor a bit while still maintaining very low impressions per minute. That would likely be the easiest solution. I think my 8x12 can run as slow as one impression every 7-8 seconds (with rollers and ink) before the torque loss causes the press to slow to a stop.

Hope this helps,

I agree with inky you have to isolate where the problem maybe coming from. How long has the press ran with the setup that you express. Not familiar with the GE line but my first question would be the amperage are you sure it is 40 and not 4, it sounds high.
If you follow the setup in the manual it should put you back to proper running if all factors are ok. There are many setting like top speed, lowest speed and of course the tourque settings. How old is the motor some older 3 phase motors can not take the pulsing from the frequency changes and pounding. There are many settings that can be altered in the controllers and they must be set properly. Make sure the motor and the drive are matched..
Good luck and maybe someone else familiar with your drive will offer some suggestions.

Turns out it has to be the motor itself. There is a little resistance when turning the shaft by hand. Removing the belt, I am able to push it forward effortlessly with my pinky.

I found a Nos dayton (vfd friendly) motor relatively cheap and will hook it up. I’ll fix the other if I can and shelf it for my next frankenstein project.