Remember that when you turn the speed down the power available will be less, using the belts or gears to keep the motor running at near its rated speed will maximise the power available. The VFD should have the motor current set to the full load current of the motor. Does the VFD error indicate an over current trip?

Mike

Looking at all possibilities (your fault is more likely with the VFD settings or installation) are the motor phase windings equal? An imbalance could lead to tripping. Is the motor a dual voltage machine?

A couple of mm depth of cut is not the whole story, by any means. Diameter, rotational speed and feed rate will all affect the power loading – as would the sharpness of the cutter and the material being worked.

The VFD may be too small (particularly if cheap chinese) as a 3 HP motor should deliver that power (2.2kW) but will require a greater input power, depending on the motor efficiency.

In the model aeroplane world, there are small devices which turn battery DC into 3-phase, with the frequency varied by a potentiometer. They are used to drive propellers and drone rotors etc.

It seems to me that the device concerned must be a very small version of a VFD. Am I correct?

The radio controlled versions must (I guess, again) be worked by a digital message – ie an on-off signal like a version of morse code. Is this right? If so, isn't this a close relative of CNC?

Regards – Tim

Colin

The motor plate shown in your Album is from a 4 pole (1450rpm) so you need to change that in parameter settings if the plated motor is on your lathe.

Emgee

I can't see a problem running a 2-speed motor from a VFD, provided only one speed range is used. A potential problem arises if both speed ranges are needed, as one would need to change parameters in the VFD (number of poles and rated current as a minimum) each time the speed range was changed. I have a vague recollection that some VFDs allow multiple parameter sets which are selected via an external switch.

Andrew

Concerning the need for parameter changes when using VFD boxes on two speed motors I suspect this isn't really needful unless running close to maximum output or wanting peak efficiency. Maybe more important with self tuning vector drive types if you want to retain the low speed torque boost ability.

Certainly the 10 hp Plug and Play VFD box supplied by Drives Direct that does a very respectable imitation of utility power in my workshop doesn't seem to care whether or not a motor is two speed or what speed its on. It just sits there driving a set of smoothing inductors at 50 hz and the normal machine controls do the rest.

That said my largest motor is 3 hp so its working well within its capabilities and, obviously, I don't use the variable speed abilities.

If Colin's Chipmaster still has its mechanical variable speed device I see no great advantages from using the VFD for variable speed. Hence odds are any sophisticated tuning parameter errors will be of little importance as 50 Hz is 50 Hz and the clever stuff is mostly to improve behaviour at other frequencies for which the motor wasn't explicitly designed.

However, as DC31k posted whilst I was typing, if Colin still has the two speed motor it can't be reconfigured to delta for 220 V input so it needs full fat 420 (nominal) volt 3 phase to work properly. I'm dubious of the ability of the so called "380 volt output" import VFD boxes being able to properly drive a UK 2 speed machine tool motor. The common designs are lovely machines but, for complex design reasons, are inherently notorious current hogs off frequency and during start up.

Clive

Edited By Clive Foster on 06/11/2021 13:08:27

Edited By Clive Foster on 06/11/2021 13:08:49

Colin before running out and buying a new VFD check that P12 is set to around 8 amps

H

Colin

Inverter Drive Supermarket are my go to supplier. Prices are reasonable and they have a well deserved reputation for going that bit further to ensure you get a device suitable for your needs.

When you say reconfigured the motor do you mean that you connected the parallel connected "double Y " windings in delta just as is done with a normal motor with single windings?

I'm told this isn't a good thing to do as it reduces efficiency and raises power consumption. Makes no sense to me as surely a pair of parallel windings is equivalent to a single winding. If it works in Y it ought to work in delta.

However there must be a reason why received wisdom is that you can't do the conversion although all the connections are there.

Clive