washdown motor for VFD

Almost certainly, this motor has an INTERNAL fan, to move heat from the windings and rotor to the case. TEFC motors have internal AND external fans.

Assuming that it does have an internal fan, it will definitely care if run at very low speeds. A computer-type fan and some cardboard or other duct to contain the airflow might make it possible to run at reduced speed with a VFD and not overheat.

Jon

Thanks Jon. Sounds like an open-frame motor and a computer fan is a better approach.

The issue of free should (automatically) make it worthwhile to investigate what's inside. Also, unless it's ancient, you might be able to locate the manufacturer's temperature specifications for this motor. The wire leads might be a clue.. the temp rating of the insulation is sometimes printed on the vinyl insulation. A rating of 125 degree C would be a good sign (with 105 being more common).

By your description of it's relative size, my WAG would be that it's very old (not bad), well designed for heat dissipation (more surface area than a typical motor that size), or that it was designed for a specific heavy duty application.

Additionally, if there is a small amount of shaft protruding from the rear bearing, you could drill & tap the shaft (and drill the rear end bell) for the addition of an external impeller to direct air over the case. If that's not appropriate, there are large sizes of muffin fans (from 12VDC to 220VAC) that would probably be suitable for cooling.

WB ..............

If you don't need washdown, and don't have a lot of dust, dirt etc. that could clog up the cooling passages in the motor, then yes, that would be the best for extended low-speed operation. A motor with a higher service factor would do better, still.

Jon