3 phase Boxford

Hi all Is it right that if an invertor is used to power the main motor it cannot also power the suds pump and light, but an convertor can.
Mike Cole
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right or wrong I use an inverter on my mill to run machine and pump but I change speeds with the belt not the inverter
Andrew
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Mike cole wrote:

Mike,
A rapid summary - apologies if you already know this.
Inverters are generally designed for 230V single/three phase input or 415V three phase input, both generate 3 phase output (at variable frequency) but they don't usually provide a voltage increase (in other words 230V in results in 230V out). Modern European 3 phase motors can usually be wired in star configuration for 415V operation or delta for 230V operation; older 3 phase motors are commonly configured internally for 415V. If you want to use an older 415 star connected motor with a 230V 3 phase inverter you need to dismantle it to find the star point and reconnect the windings in delta - possible, but fiddly and not for the faint hearted.
If you run from a 415V static converter (eg Transwave) the lathe motor is used to "generate" a third phase; it's essential that this is running before the suds pump is switched on (otherwise the suds pump may be damaged) and you need to make sure that any controls (contactors, transformers, etc) are not connected to the artificial phase. Because the converter contains a 230-415 transformer you don't need to change motors from star to delta. If you use a rotary converter (effectively a static with it's own "pilot motor") there is no need to observe these precautions.
You can run from a 415V 3phase inverter by providing a 240-415 transformer on it's input but there's a slight loss of inverter output transient capability because of the single phase input. I'm currently doing this with a Holbrook lathe and it works very well.
If you run from a 230V 3 phase inverter you need to wire the motors in delta and connect them directly to the inverter output. Remember also that in a 3 phase lathe there will be at least one 3 phase 415V contactor, and probably a single phase 415 transformer to provide power for the LV light; these will require rewiring/replacing. When I did this on a Boxford (and a Chipmaster) I just used the inverter to drive the lathe motor and had a separate single phase feed to the controls and the suds pump (with a phase shift capacitor). Lots of fiddling about but it worked well.
I really am sorry if all I've done is told you things that you already know. The bottom line is that you CAN use an inverter to drive both motors (providing they are both wired star/delta as appropriate for the voltage) but if you use the variable frequency capability of the inverter your suds pump will change it's speed (you may not want that).
Dave
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Thank you, that was what I wanted. As the lathe is alreadly wired up to a transwave converter I think I will stick with that and use the belts to change speed.
Mike Cole
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