Thread: Single phase input VFD to 3ph output on a lathe

Hi, I've just connected a new VFD to the 3ph 415v 2 speed motor of my lathe. Problem; The motor will now run up to full speed (2800) no problem, BUT only after I give the pully an initial push start. The VFD is a Nflixin single phase 240v input to 3ph 380v output. I've changed a few parameters in settings, eg. speed to 2800, acceleration time to 5 seconds, volts to 415 but nothing else. Motor is around 50 years old but seems to run very nicely once going.
Thanks

Maybe it dosen’t like too much variance from the 50Hz it was designed for?

Unsure though as most people seem to rave on about how much range of speeds they can get from a vfd

are you sure you have 415v across all three phases at the motor terminals?

are you saying the motor is a 2 speed motor? and you have tried to configure accordingly to work from the VFD on both speeds?

Can you post a picture of the Data Plate on the motor?

I wonder if it is wired correctly. Sounds like one phase is not there.

Originally Posted by eskimo

are you sure you have 415v across all three phases at the motor terminals?




are you saying the motor is a 2 speed motor? and you have tried to configure accordingly to work from the VFD on both speeds?

I did check static and running but for some reason when running the voltage was jumping around too much for me to understand. Maybe my multimeter wasn't up to the task.
Measuring from motor terminals while running multimeter also kept flipping over to DC.


Yes 2 speed 700 and 2800 but haven't run it from the 700 side.

According to those with the same motor it can only be run on one speed.

Originally Posted by Metalmachine

Maybe it dosen’t like too much variance from the 50Hz it was designed for?

Unsure though as most people seem to rave on about how much range of speeds they can get from a vfd

I could vary the speed quite a bit until it went too low.

VFD maker data label.jpgEMB motor plate.jpg

Originally Posted by Techo1

Can you post a picture of the Data Plate on the motor?

Originally Posted by .RC.

I wonder if it is wired correctly. Sounds like one phase is not there.

Thinking now of bypassing lathe connections and wiring directly from VFD to the motor.

Originally Posted by Metalmachine

Maybe it dosen’t like too much variance from the 50Hz it was designed for?

Unsure though as most people seem to rave on about how much range of speeds they can get from a vfd

If I turn VFD up to 50hz, motor still won't start without a push, but once running I can vary speed with the VFD.

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Updated Nov 28 2022

The 3 phase motors I’ve seen run with a missing phase (when a phase was lost in the building) ran slowly and with obvious growling sounds.

How have you got it wired into the lathe switches? The VFD should have Phase Loss Protection so it would not run at all unless 3 phases were available.

I am guessing that 1 phase is missing. Wire direct to motor as you suggest.

I've now noticed that the motor will keep running even when frequency is turned down to around 3.5hz