VFD setup help

Soooorta.

So the drive needs to be 135v or it will toast the spindle. BUT, you are 100% right in that lowering the voltage has some some sort of math and reduced the power.

After working with the drive support people, we did a few things. ! was to boost the carrier frequency to 16khz. this reduced current a lot (over an amp at load). Then we upped the voltage bit by bit until we found a compromise where it is no longer bogging down, but also not getting more than slightly warm. Idles at 2.1A now.

As a result, I have about 600w usable power at 5A draw, no bogging down, and it's "fine" for now, until I can wrangle a high speed drive.

Well, I better bow out, you sound quite sure that your motor speed is voltage-dependent not hz/poles like an AC induction motor.
Might be worth throwing some info on the motor up here - surely someone in the linuxcnc community has used a similar unit.

AC induction motor voltage is speed dependent in the same way as DC motors.
They are more complex because of things like field weakening in the the armature,
but the basic behaviour is the same.

That is if you took a 240V 60 Hz AC induction motor and ran it at 1/2 speed at 30 Hz
you would need to reduce the voltage to approximately 120 V to avoid overcurrent/saturation

Yes. But apparently setting a 220v 1000hz motor to 135v and 600hz on this drive is not the same as just moving down the VF curve on a 1000hz drive. The engineer was confused as much as me. It should "just work" but it doesn't.

And of course as I found out, faster drives are not easy to get so I'm stuck with this compromise we found for now.

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I am surprised by this engineer's statement. If you can't give full voltage, you can't expect full power. Power is the product of volts * amps. If this engineer gets full power with half the voltage, he can do magic. The motor and VFD must fit together. Frequency-controlled motors have characteristics such as torque and frequency, or torque and power. Not easy to read or calculate. But I would say full power is only possible if everything fits.

Not full power. Full torque. This is a common response form people on the issue. No one ever stated we expected to get a full 1.5kw at 60% speed. we expect 900w.

The torque should not change as speed(voltage) lowers normally, especially with a vector drive. I was getting half the expected torque and the spindle would not stay at speed. This means something unexpected was happening when the voltage was lowered that would not happen on a 1000hz drive that was simply set to 600hz.