The motor data plate indicates 400v three phase, connected in Y (wye/star).

To attach a VFD directly to that motor with no modifcation would require a VFD that outputs 380v three phase from a 230v single phase input. These are available as AT4 (not AT1).

A second option is to locate the star point of the motor and reconfigure it to delta connected. This can be a more or less easy job depending on how the motor is manufactured. Then an AT1 VFD would work.

<p style=”text-align: left;”>Should have said converters not convectors</p>

A VFD doesn’t remove the need for moving the belt to different pulley positions Mark. It will lessen those changes as long as the tooling diameter and what the tooling is built from, HSS v Carbide are similar when changing those cutting tools. From my own perspective, using a VFD on my own step pulley turret mill was one of the best decisions I made because of all the extra motor control options. Yes you can get a fair amount of torque even down into the 25 Hz range, but the length of time your using that motor at those reduced speeds becomes important since the motors own cooling fan is also running at that reduced rpm as well. Extra heat the motor wasn’t designed for will only lessen it’s life span if that motor is being operated for too long at reduced rpm.

Most but not all VFD’s today are capable of either forward or reverse motor direction. If your mill does have a back gear, then you also require a VFD that does allow switching to either motor direction since that back gear reverses the spindle rotation once it’s engaged. I’d also suggest that how well the user manual has been done might be as important as the VFD itself. Without a clearly written manual, the initial end user programming for what you want to have available such as ramp up / down times, pre set motor speeds etc, can become a real issue. And as long as it’s well explained, none of it is hard to do. I also wouldn’t under size or buy any VFD that’s just barely adequate for the job. For higher than the motors rated rpm and at the highest pulley speed ratio, my own industrial quality VFD would fault out due to the extra torque required during a motor start. Increasing the motors ramp up time of a few seconds more cured that.

If you simply connect a common 220 V nominal output VFD intended for use with a 220 v delta connection to a Y (star) 440 V motor maximum power will be approximately 60% of the nameplate rating.

Basically the VFD bus runs out of volts so it switches to constant power mode at about 29 hz,  just over 800 rpm.

Which may well be enough. Thats a 2 hp motor so maximum power will be reduced to 1.2 hp. I presume the mill is a Bridgeport clone, my Bridgeport has a 1.5 hp motor and has, so far as I can see, never run at anything approaching full power in my hands.

Clive