VFD for myford ml7

Hi Myfordians

I daresay this question has already been asked, if so pls link me. I ask if anyone has converted the original BC 1/2hp sp 240 v motor for use on a vfd. Note this has start and run windings controlled by a centrifugal switch (not capacitor start).

Will bearing arcing be a problem provided I screen and earth properly

How do I switch to reverse safely? Stopping first of course

Will this type of motor provide dynamic braking and need a db resistor?

I am not looking for a wide speed range say 20 to 150%

Im floating in the dark here in a pool of techno babble

Robin

Hello Robin,

In a word no, you need to fit a three phase motor.

Michael

+1 to Michael's response.

And to add that braking a threaded chuck can cause the chuck to unwind. Also beware that you may be over-speeding parts of your equipment at 150%.and continuous working, at below about 50%, can cause overheating (the motor fan is running at half speed also).

While it is not strictly true that single phase motors cannot be used with a VFD the motors need to be of a specific type. The motor you have is unsuitable so as mentioned above you will need a three phase motor suitable for a voltage of 220v between phases, this will usually be achieved by using a motor that is 400v between phases connected in star and 220v connected in delta. Some small motors do not have all six wires brought to the terminal block so the the conversion will involve the wretched business of finding the star point which will be loomed and varnished into the windings. Best to check any motor of interest has six wires brought to the terminal block. A careful study of the information plate on the motor will usually show the star and delta voltages if this connection is possible. Ready made packages are available for myfords and this may be the simplest way to go although not the cheapest. The advantage of a package is that it will work straight out of the box and the inverter will be set up and optimised and be safe. It is not to difficult to put the parts together and even make it work but as usual there is a right way and a wrong way to do things and looking at some of the installations on people's machines they do not meet any sort of standard or recommended design from the manufacturer. Two issues are important, electrical safety for the user and proper design of the installation to protect the inverter and the motor.

Mike

Edited By Michael Poole on 20/06/2016 19:02:44

Hi Robin,

I fully support Michael Poole's thoughts and have just very recently purchased, and installed, a complete system from Transwave onto my ML7 Tri-Leva.

The package comprised of the VFD, the brand new motor, the remote control plus all the necessary cabling to complete the installation, including the initial 240v power to the VFD.

The change is spectacular in giving me effectively three complete ranges of speeds at the flick of a switch and the turn of a rotary knob.

The installation was extremely straight forward and the wiring instructions simplicity themselves, though I would suggest placing the VFD unit into an enclosed vented box to ensure that all the numerous wiring connections are nice and tidy and safe.

Mike