New to VFD... Need some advice...

[abasir]

I picked up a high speed water cooled spindle (400Hz, 24000rpm, 800W, 150V) few days ago. It came with an inverter/VFD that can output 1500Hz, 1500W, 400V. Both are aliens to me...

The VFD allow for custom voltage/frequency curve. Default setting for VF curve is linear (20Hz, 10V to 400Hz, 125V). Is there any potential problem if I set the custom VF curve as follows as I need to get good torque at low rpm too... currently, I can stop the spindle with my finger when it's running around 1000rpm...

Voltage: Min 75V Mid 100V Max 125V
Frequency: Min 10Hz Mid 30Hz Max 400Hz

Also, can I set the VFD output voltage max at 150V (same as spindle nameplate voltage ratings).

Spindle and VFD photo here ...

[rdpzycho]

experiment with custom settings. just never feed any voltage above 150V to the motor.

linear curves are good for some motor. if you cannot find the spec of your motor then just experiment with it.

supposedly, at 1000 RPM you must be getting lots of torque (constant torque region). that's 16Hz ofr 1000 RPM, roughly.

you can even have a constant voltage curve, but the toqrue curve would not be constant. it is the main reason the VFD's are tend to be programmed in a linear V/F fashion..

[HuFlungDung]

If you are running low rpm because you are using a larger diameter tool, this is exactly backwards to the torque requirements of the tool load. A reduction (belt or gear) is the best way to amplify the motor torque at low speeds.

Its been my experience that running a motor with a vectorless VFD on low frequency will have a quite mushy response to load. To overcome this, you need:
a: a larger motor, or
b: feedback from the motor to the inverter. A Vector drive (with encoder feedback from the motor shaft) is the way to really get consistent torque at low rpm.

The next best thing is a reduction drive between your motor and spindle that will permit you to boost the motor rpm for those lower spindle speeds.

[rdpzycho]

it's a bit of trial and error when playing with vectorless VFD's..my father always plays with the curves to get the best out of a motor without resorting to vector drive (he is mostly left with vectorless VFD from a client)..the motor is used for a different environment though, Cargo Elevators..

[rdpzycho]

by the way, there are sensorless vector drives, in case you would be considering switching to them..