Centroid Community CNC Support Forum

Thank you for the additional info gents. That's a lot of info for me to absorb. I may actually have some time to mess with it tomorrow.

Just out of curiosity, what could I be looking at for a new single phase VFD? Guessing about as much as having mine repaired and then still having to deal with 3-phase. Would be wonderful to not have to deal with 3 phase at all.

Mark

You are going to need a 3 phase VFD. There might be one out there that is designed for single phase @7.5 hp, but I think it is an off brand. You can run a 3 phase VFD on single phase, but you need to derate the VFD. The general rule of thumb is to double the HP, ie a 15 hp vfd for a 7.5 hp motor, but current is most important. So start comparing the current ratings of a 15 hp unit to your motor, and move up to a larger size if the ratings are not met.

Please post a picture of the NAMEPLATE of the spindle motor.
I had a Bridgeport Romi Lathe. That lathe was fitted with a 5ph motor and LEFT here with a single phase VFD.
It was the gear head lathe.

As was previously mentioned, you could find a 15hp VFD and potentially use it on single phase. That VFD you have may well run on single phase. Do you intend on pushing your lathe to 7.5hp??

DO, as I suggested. Put single phase 240 to the spindle drive and the Servo drives directly, see how they respond. Look up any error codes on the display. You have nothing to lose in my opinion.

Marty

Here's an older shot of the tag on the motor. Can you read it and does it have what you're looking for? If not, I can try for a better pic.

I don't ever intend to push the lathe to it's limits. I tend to baby the equipment in my home shop because I can, and I don't run production.

Chevy427z wrote: ↑Thu Jan 06, 2022 11:46 pm Here's an older shot of the tag on the motor. Can you read it and does it have what you're looking for? If not, I can try for a better pic.

I don't ever intend to push the lathe to it's limits. I tend to baby the equipment in my home shop because I can, and I don't run production.

Looks like a coolant pump motor at 1/10 up and .5amp at 220vac?

Yeah, I am with Marty. That is the coolant pump motor. Current is way too low. Even if you baby the machine you should not use a smaller VFD. It is the startup current that will take the VFD out, and as I mentioned a lathe has a very large inertial load presented to the motor. It is far harder to start than any mill. My 7.5 hp lathe startup current is 100a- but my motor is also a pig. A VFD helps with the startup due to it ramping up, but there is still a higher current presented to the VFD trying to get that spindle rotating. Match the current rating of your motor to the VFD and go a bit higher if possible.

Here is a 7.5 hp single phase VFD. Again, current is what counts.

The stupid Amazon links don't work here, but you can search it up.

The NEC requires upsizing the service to a VFD 125%, so whatever the current rating of the VFD is you need to increase it. You would probably end up with a 60A feed to it, which is not bad.

I agree with Marty, try feeding single phase to that converter and see what happens.

martyscncgarage wrote: ↑Fri Jan 07, 2022 12:14 am
Looks like a coolant pump motor at 1/10 up and .5amp at 220vac?

Oops. I thought it looked a little odd. I will try to get a shot of the spindle motor this afternoon, and see if I can't figure out how to get single phase to the drives.

Just when I thought I was beginning to understand.. I am more confused now. Is this not a spindle motor?? It ran like a 7.5 HP machine for a little while when I first bought it. This is the motor with the 1/10 label on it.

I will post pics of the coolant pump in the next post to keep things separate.

Coolant pump and label

This is the spindle drive. Posting these pics to ask where I connect the 220 single phase so I don't blow anything up. I am assuming L1 and L2.