Re: [CAD_CAM_EDM_DRO] VFD and inverter duty 3phase motors

Lance Hopper wrote:

>Hello,
> I've got a 5HP Automation Direct GS2 AC (0-400Hz) drive. I'm
>looking to buy a 3-5HP 220VAC 3phase ~3500RPM motor for a small lathe
>application. I've been doing some looking and it seems that there
>are motors that are "inverter duty" rated. The inverter duty motors
>seem to have a rated speed like 1725RPM @60Hz, and then have a 'max
>safe speed' usually rated much higher like 3450+RPM. I'm guessing
>this max speed is at 120Hz. Also it seems that inverter duty motors
>have a much better spread of torque than standard motors made to
>operate at or close to the rated RPM only.
>
> Should I just get a regular ~3450RPM @60Hz motor, and limit my VFD
>to 60Hz, or should I go for an inverter duty motor where I can run
>much higher frequencies/speeds. Any comments would be appreciated.
>
>
>

A standard 1750 RPM motor rated at X HP should have twice the torque
at that RPM as the same HP motor at 3450 RPM. It may also be larger
and heavier. As for "inverter duty" that mostly applies to the motor
winding's
insulation. I think a dual-voltage motor rated for 230/460 V service has
about the same insulation at much lower cost. If you run a 230 V input
VFD into a motor rated for 230/460 V, you should have no trouble with
the motor.

Jon