Another VFD question. Is it worth buying a higher capacity unit?

[Neale]

My own combi machine is saw/spindle moulder - planer is separate machine - but all 240V/1P so haven't had this problem. I guess that you normally change over between motors while nothing is running, so I guess the usual kind of VFD would work.However, I don't really like the sound of it, thinking about how you would isolate the motors for blade/cutter changing/adjusting. VFD that is happy to be to have its output switched live seems like the best way to go.

[Richard]

My own combi machine is saw/spindle moulder - planer is separate machine - but all 240V/1P so haven't had this problem. I guess that you normally change over between motors while nothing is running, so I guess the usual kind of VFD would work.However, I don't really like the sound of it, thinking about how you would isolate the motors for blade/cutter changing/adjusting. VFD that is happy to be to have its output switched live seems like the best way to go.

If it was going to be problem to change the motor select switch while the VFD is actually powered up (motor not running), I guess I would have to make an interlock type cover over the motor select switch to enforce complete isolation of the VFD before changing motors.

If it's just a case of waiting for the motor to stop, then I don't think thats going to be a problem.

I doubt I'll be hopping from saw to spindle and back, so the machine will be set up for sawing or planing or routing and be used like that for some time.


I will ask the supplier and see what they say.


I did read somewhere that VFD's don't like contactors etc inline with the motor, but I have also read that people just wire them up to the main input of the machine and they work ok. No bypassing of contactors, etc.

[Neale]

I did read somewhere that VFD's don't like contactors etc inline with the motor, but I have also read that people just wire them up to the main input of the machine and they work ok. No bypassing of contactors, etc.

I think that that's pretty much the point at issue - the common lower-power VFDs don't like live switching - don't put any kind of switch/relay/contactor between VFD and motor - and some (the better ones? Read "cost more...") are OK. Have to check with supplier to find out which is which!

[JAZZCNC]

I think that that's pretty much the point at issue - the common lower-power VFDs don't like live switching - don't put any kind of switch/relay/contactor between VFD and motor - and some (the better ones? Read "cost more...") are OK. Have to check with supplier to find out which is which!

Provided the VFD isn't outputting power and the motor is stopped then it's not a problem to switch between motors. I've done this with HY VFD switching between spindles using contactors without any problem.

Regards powering 2.2Kw motor with high startup load then I'd say it's do-able if VFD is setup correctly but better with larger VFD to give extra overhead and less stress on VFD.