Do you know that, or did someone tell you? In my manual the spindle motor part number is the same on both 415V (UK) and 220V/380V (European) schematics.

I run my M300 on 3-phase so I'll avoid the debate about VFD plus 3-phase motor versus single phase motor. Although in either case the switch gear may well not work, nor may the coolant pump.

Andrew

Sigh, that is incorrect. Here's the plate from the 3-phase motor I bought to drive my Pultra lathe:

The two lines for 230V delta and 400V star have identical powers.

Andrew

Hi,

I am only going by my experience with the M300 I worked on.

In "star" the lathe starts in it's top speed of 2800 almost instantly but in "delta" it would not start until we adjusted the "ramp up" setting. I cannot remember the figure we set in the VFD but it did start after a few seconds.

The VFD supplier said in the paperwork that there would be a reduction in torque when running in "delta"

Although the motor on the M300 is reasonably accessible my lathe is up against a wall. I've had a quick look but can't immediately see a ratings plate anywhere on my motor. Going on the experience of Alistair who has recently installed one the terminal block has six contacts which means it is dual voltage. Being a cynical old git I wouldn't put it past the manufacturer to buy dual voltage motors but mark them as 415V only in order to charge more for a dual voltage motor option.

A motor designed to run at 415V in star will expect 240V in delta, ie, divide the voltage by the square root of three.

Andrew

I don't understand why they would say that? The frequency doesn't change, so neither does the speed. Given that the plate I showed indicates that the output power stays the same then the torque must also stay constant.

Remember that the phase currents in delta are higher than in star. So if the current limit in the VFD wasn't increased that may explain why the motor didn't start properly in delta. The start currents will also be proportionally higher so may be the VFD was going into current limit? A longer ramp time may ameliorate that.

Andrew

The converter referenced by Dave at Home Workshop ad 28540 is a Motorun static converter.

Decent quality unit but very old now. 30, maybe 40,+ years I think. I had one and found it worked much better when turned into a pseudo rotary converter by adding a permanently running pilot motor. 2 or 3 hp that I had just kicking around I think. Eventually sold to a man with a Colchester Student who was well pleased.

Big issue with static converters is that they can never achieve proper phase balance, unless you get lottery win lucky and hit the sweet spot, because the capacitor values needed vary with both motor size, type and load. The maker provides a best guess approximation.

Don't futz about. Get yourself a decent brand name vector drive inverter from the likes of Inverter Drive Supermarket, the folk I use, or one of the other Forum Recommended good guy suppliers and hook up your motor. Even if it doesn't have a 6 terminal junction box opening up a relatively modern motor to find the star point is pretty easy as its generally right on top of the windings. Pretty much anything made after about 1960 will be dual voltage windings by design even if thruppence ha'penny was saved by not using a 6 terminal connection box. Older designs often have it somewhat buried.

With a good vector drive inverter used between nameplate ± 1/3 rd rpm in conjunction with the mechnical speed settings you will never notice that its not on full fat 3 phase.

Clive

I was discussing the star/delta thing today with our old plant engineer and when I said there was no difference in star or delta windings and output he said "well why do we need Star Delta Starters for larger motors?" He couldn't remember the de-rating percentage off hand but it was always listed in the motor and starter configuration paperwork.

Most of the VFD's used for small motors from domestic mains also output 240V three phase. I set the connections in the motor i bought to delta to suit that. If the motor had been left in star, it might have run, but at reduced output, as star usually used 415V.